WO2015135976A1 - Polymyxin derivatives and their use in combination therapy together with different antibiotics - Google Patents

Polymyxin derivatives and their use in combination therapy together with different antibiotics Download PDF

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Publication number
WO2015135976A1
WO2015135976A1 PCT/EP2015/055046 EP2015055046W WO2015135976A1 WO 2015135976 A1 WO2015135976 A1 WO 2015135976A1 EP 2015055046 W EP2015055046 W EP 2015055046W WO 2015135976 A1 WO2015135976 A1 WO 2015135976A1
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Prior art keywords
compound
group
nitrogen
carbon
alkyl
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PCT/EP2015/055046
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French (fr)
Inventor
Pamela Brown
Michael Dawson
Mona SIMONOVIC
Steven Boakes
Esther DUPERCHY
Steven James Stanway
Antoinette Wilson
Stephen Frederick Moss
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New Pharma Licence Holdings Limited
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Priority claimed from GB201404301A external-priority patent/GB201404301D0/en
Priority claimed from GB201421019A external-priority patent/GB201421019D0/en
Priority to SI201531832T priority Critical patent/SI3116897T1/en
Priority to PL15715172T priority patent/PL3116897T3/en
Priority to LTEPPCT/EP2015/055046T priority patent/LT3116897T/en
Priority to CA2940455A priority patent/CA2940455C/en
Priority to RS20220387A priority patent/RS63138B1/en
Priority to KR1020167027152A priority patent/KR20160135739A/en
Priority to DK15715172.1T priority patent/DK3116897T3/en
Priority to EP15715172.1A priority patent/EP3116897B1/en
Priority to ES15715172T priority patent/ES2910072T3/en
Priority to CN201580011858.0A priority patent/CN106232617B/en
Priority to HRP20220387TT priority patent/HRP20220387T1/en
Priority to AU2015228898A priority patent/AU2015228898B2/en
Priority to KR1020237036093A priority patent/KR20230152779A/en
Priority to MX2016011682A priority patent/MX359104B/en
Priority to RU2016139978A priority patent/RU2740190C2/en
Priority to JP2016556784A priority patent/JP6785659B2/en
Application filed by New Pharma Licence Holdings Limited filed Critical New Pharma Licence Holdings Limited
Priority to US15/125,415 priority patent/US20170073373A1/en
Publication of WO2015135976A1 publication Critical patent/WO2015135976A1/en
Priority to IL247243A priority patent/IL247243B/en
Priority to US17/157,393 priority patent/US20210221848A1/en
Priority to US18/126,270 priority patent/US20230322858A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides
    • A61K38/04—Peptides having up to 20 amino acids in a fully defined sequence; Derivatives thereof
    • A61K38/12—Cyclic peptides, e.g. bacitracins; Polymyxins; Gramicidins S, C; Tyrocidins A, B or C
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K7/00—Peptides having 5 to 20 amino acids in a fully defined sequence; Derivatives thereof
    • C07K7/50—Cyclic peptides containing at least one abnormal peptide link
    • C07K7/54—Cyclic peptides containing at least one abnormal peptide link with at least one abnormal peptide link in the ring
    • C07K7/60—Cyclic peptides containing at least one abnormal peptide link with at least one abnormal peptide link in the ring the cyclisation occurring through the 4-amino group of 2,4-diamino-butanoic acid
    • C07K7/62—Polymyxins; Related peptides
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
    • A61P31/04—Antibacterial agents
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K38/00—Medicinal preparations containing peptides
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/30—Against vector-borne diseases, e.g. mosquito-borne, fly-borne, tick-borne or waterborne diseases whose impact is exacerbated by climate change

Definitions

  • the present invention relates to novel compounds, combinations of compounds, pharmaceutical compositions comprising the compounds and the use of the compounds, pharmaceutical compositions and combinations for treatment, for example treatment of microbial infections, particularly those caused by Gram-negative bacteria.
  • Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumanii can cause serious infections, such as pneumonia, urinary tract infections, skin and skin structure infections such as wound infections, ear infections, eye infections, intra-abdominal infections, bacterial overgrowth in the gastrointestinal tract and bacteraemia/sepsis.
  • the treatment of serious bacterial infections in clinical practice can be complicated by antibiotic resistance.
  • Recent years have seen a rise in infections by Gram-negative bacteria which are resistant to many types of antimicrobials including broad spectrum antibiotics such as aminoglycosides, cephalosporins and even carbapenems.
  • Polymyxins are a class of antibiotics produced by the Gram-positive bacterium Bacillus poly my xa.
  • polymyxins particularly polymyxin B and polymyxin E (colistin, usually as its prodrug colistin methane sulphonate) were used in the treatment of Gram-negative infections.
  • these antibiotics exhibited side effects such as neurotoxicity and nephrotoxicity.
  • the polymyxins now play an important role in the therapy of MDR Gram-negative infections due to the lack of viable alternatives. However, their use in therapy is limited to treatment of last resort.
  • WO 2008/017734 tries to address this toxicity problem by providing polymyxin derivatives carrying at least two but no more than three positive charges. These compounds are said to be effective antibacterial agents with reduced renal toxicity. It is hypothesised in the disclosure that the reduced number of positive charges decreases the affinity of the compound for isolated rat kidney tissue which in turn may lead to a reduction in
  • WO 2010/075416 provides urea linked aryl polymyxin decapeptides including CB182,804, which is reported to have similar activity but reduced renal toxicity compared with polymyxin B. Phenyl cyclopropane polymyxin derivatives are also described in
  • WO 2012/168820 provides a further series of polymyxin derivatives reported to have reduced toxicity, and sometimes enhanced activity compared with polymyxin B, in which the diaminobutyrate group at position 3 in the tripeptide side chain is replaced by a
  • polymyxin derivatives which have reduced toxicity compared to polymyxin or colistin and are particularly effective against Gram-negative bacteria.
  • the present invention provides a polymyxin compound of formula (III), as described herein, and its use in a method of treatment or prophylaxis,.
  • the compounds of formula (III) may be used to treat a microbial infection, such as a Gram-negative bacterial infection.
  • a polymyxin compound of formula (III) and pharmaceutically acceptable salts, protected forms, solvates and hydrates thereof, such as pharmaceutically acceptable salts, and hydrates thereof.
  • a pharmaceutical composition comprising the polymyxin compound of formula (III) together with one or more
  • a polymyxin compound of formula (III) or a pharmaceutical composition comprising the polymyxin compound of formula (III) for use in a method of treatment of prophylaxis.
  • a polymyxin compound of formula (III) or a pharmaceutical composition comprising the polymyxin compound of formula (III) for use in a method of treating a bacterial infection.
  • the compounds of formula (III) or a pharmaceutical composition comprising the polymyxin compound of formula (III) are suitable for use in the treatment of fungal infections.
  • polymyxin compound of formula (III) for use in a method of treatment or prophylaxis, in combination with an active agent, such as where the active agent has activity against Gram-negative bacteria.
  • the present invention provides compounds of formula (III) and their use in medical treatment.
  • the compounds of formula (III) are polymyxin compounds having an N terminal group that contains amino functionality.
  • the N terminal group has a nitrogen-containing heterocyclyl (or heterocyclylene) group and/or a
  • the compounds of formula (III) have suitable antibacterial activity whilst also apparently exhibiting less toxicity, especially nephrotoxicity.
  • the compounds may have comparable or improved biological activity compared to Polymyxin B or Colistin against one or more of E, coii, P. aeruginosa, K. pneumonia, or A. baumannii bacterial strains. Such compounds are useful alternatives to the polymyxin type compounds previously described in the art.
  • polymyxin compounds or polymyxin derivatives in the art are known or suspected to have a poor toxicity profile.
  • compounds having a fatty acyl chain at the N terminal such as Polymyxin B and Colistin, is associated with
  • Vaara et ai. (Antimicrob. Agents Chemother. 2008, 52, 3229) have suggested that the pharmacological and toxicity properties of a polymyxin compound may be altered with changes to the polymyxin polypeptide sequence.
  • Vaara ef ai. have prepared a polymyxin compound having only three positive charges, whereas the polymyxin B nonapeptide carries five positive charges.
  • the present inventors have shown that adaptations to the N terminal of a polymyxin compound may reduce nephrotoxicity. As described herein, the N terminal has a substituent containing an amino group (which may be in the form of a nitrogen-containing heterocycle).
  • the compounds of formula (III) are capable of increasing the antimicrobial activity of a second antimicrobial agent, such as rifampicin.
  • a second antimicrobial agent such as rifampicin.
  • Such combinations have comparable or improved biological activity compared to the combination of the second agent with Polymyxin B or Colistin, for example against one or more of E. coli. P. aeruginosa. K. pneumonia, or A. baumannii strains.
  • compounds of formula (III) may have comparable biological activity compared to Polymyxin B or Colistin against one or more of E. coli, P. aeruginosa, K. pneumonia, or A. baumannii strains.
  • when such rifampicin have comparable or improved biological activity compared to the combination of the second agent with Polymyxin B or Colistin, for example against one or more of E. coli. P. aeruginosa. K. pneumonia, or A. baumannii strains.
  • compounds of formula (III)
  • the combination has unexpectedly superior activity compared to the combination of Polymyxin B or Colistin with the same active agent.
  • the compounds of formula (III) may also posess an inherent antimicrobial activty.
  • each compound of formula (III) is active against a broad range of bacteria and each compound is capable of potentiating the activity of a second active agent, for example against E. coli. P. aeruginosa, K. pneumonia, or A. baumannii strains.
  • a second active agent for example against E. coli. P. aeruginosa, K. pneumonia, or A. baumannii strains.
  • the compounds previously described in the art have a varied profile of biological activity, and it is difficult to predict the extent to which a particular polymyxin compound will potentiate the activity of a second agent.
  • the compounds of formula (III) have excellent microbial activity whilst also exhibiting less toxicity compared to Polymyxin B or Colistin, for example as measured against HK-2 cells. In some cases the compounds are active even against microbial strains which are resistant or have reduced susceptibility to Polymyxin B and Colistin. The activity is associated with the presence of amino functionality at specific locations within the N terminal group. Further improvements in activity are also found where certain substituents are present in the N terminal group, and the chiral centres in the terminal group have a specific stereochemistry.
  • the compounds of formula (III) are N-terminal derivatives of the polymyxin series of compounds.
  • the core of the compound of formula (III) is a nonapeptide version of a polymyxin compound, such as deacylated polymyxin B nonapeptide (PMBN,
  • the present inventors have found that the group attached to the N terminal of a polymyxin nonapeptide is an important determinant of biological activity and compound toxicity.
  • the inventors have identified certain N terminal substituent groups that show enhanced activity and/or exhibit less toxicity compared to Polymyxin B or Colistin.
  • the amino acid residue at position 1 is a diamino butyric acid (Dab) residue which is acylated at its N-terminal with a fatty acyl chain.
  • Dab diamino butyric acid
  • the N-terminal group of Polymyxin comprising Dab and the fatty acyl chain is replaced by an amine-containing moiety which is linked to a further substituent, but not linked via an amide bond.
  • polymyxin nonapeptides are known in the art for use in the treatment of microorganisms.
  • the present inventors looked at the activity of three polymyxin B analogues against a range of microorganisms. As with other researchers, the inventors found that the deletion of the Dab residue at position 1 in Polymyxin B had little effect on the activity of the compound (compare compounds CC4 and CC6 in Table A below). However, when the inventors looked at a further analogue where the Dab residue was replaced with Gly, a substantial deterioration in biological activity was noted (compare CC5 and CC4). The inventors believe that the presence of amino functionality at the terminal of a polymyxin compound is important for maintaining activity. Thus, the compounds of the invention include amino functionality at the N terminal of a polymyxin compound. The polymyxin B nonapeptide structure is shown below, where -R is a modification of the N terminal group.
  • the inventors believe that, for optimal activity, an amino substituent is required to mimic the Dab side chain in the naturally-occurring polymyxin structure.
  • the inventors have therefore provided compounds of formula (I I I) where an amino group -NR 16 R 17 or -N(R 16 )- is provided at a carbon atom that is ⁇ or ⁇ to a group -X- at the N-terminal of a polymyxin nonapeptide.
  • the group -X- may be regarded as equivalent to the carbonyl portion -C(O)- of an amino acid residue at position 1 .
  • the inventors have found that compounds where an amino group is provided solely at a carbon atom that is a to the group -X- have inferior biological activity (compare CC7 with example compounds D4 and D6 in Table B).
  • the data are MIC values at g/mL.
  • the stereochemistry is an important determinant of activity, for example where an additional substituent is provided at the carbon atom that is a to the group -X-.
  • it is preferred that the stereochemistry at this position is the same as that of the L-Dab residue in Polymyxin B (compare compound D29 prepared from optically active carboxylic acid with diastereomers D24 and D25 in Table D, where B7 is Example 12 in WO 2013/072695).
  • the data from Table D also shows the importance of a substituent group: compare B7 with D29, for example.
  • nonapeptide and the data are MIC values at pg/mL Absolute stereochemistry is depicted by heavy or dashed wedges.
  • the amine group may be part of a nitrogen-containing heterocycle.
  • WO 2013/072695 describes compounds having a nitrogen-containing heterocycle at the N terminal of a nonapeptide. However such compounds are not substituted. The inventors have found that the addition of a substituent improves activity.
  • the compounds of the invention therefore, where the amine -N(R 16 )- is part of a ring structure, have a ring substituent (compare B8 with example compounds D2 and D39 in Table E, where B8 is Example 13 from WO 2013/072695). Table E
  • the compounds of formula (II I) are characterised over the polymyxin deca peptides for the reason that the compounds of formula (I I I) do not possess the amide functionality of a polymyxin that is formed from the amino group at the a carbon of the L-Dab group at position 1 and the fatty acyl chain.
  • an amino group is provided at the a carbon, it is not part of an amide group.
  • polymyxin deca peptide derivatives having a short acyl chain e.g. butanoyl
  • polymyxin B see de Visser et al. J. Pept. Res. 2003, 61, 298
  • Compound D9 (see Table C) has a short isobutyl moiety attached to an aminobutyric acid moiety. It is an analogue of the alkanoyl derivatives described by de Visser, yet it does not include the amide group of those derivatives.
  • Compound D9 has a similar biological activity to the natural polymyxin, and it is 12 times less toxic than polymyxin B (as measured in relation to I C3 ⁇ 4 values in a HK-2 assay).
  • the present invention provides a compound of formula (III) and the use of this compound in a method of treatment.
  • the compound of formula (III) is represented thus:
  • -X- represents -C(O)-, -NHC(O)-, -OC(O)-, -CH 2 - or -SO2-;
  • -R 4 is C1-6 a Iky I substituted with one hydroxyl group or one amino group;
  • -R 15 is an amino-containing group:
  • -R A is hydrogen or -L A -R M ;
  • -Q- is a covalent bond or -CH(R B )-;
  • -R B is hydrogen or -L B -R BB ; or, where -Q- is -CH(R B )-, -R A and -R B together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or -R A and -R B together form a 5- to 10-membered monocyclic or bicyclic heterocycle; and, where -Q- is a covalent bond, -R A is -LA- ⁇ , and where -Q- is -CH(R B )- one or both of -R A and -R B is not hydrogen; -R 16 is independently hydrogen or C1-4 alkyl;
  • -R 17 is independently hydrogen or C1-4 alkyl
  • -Q- is -CH(R B )-, -R 17 and -R B together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle; and where -R 17 and -R A together form a monocyclic nitrogen-containing heterocycle, each ring carbon atom in -R 17 and -R A is optionally mono- or di-substituted with -R c , and the monocyclic heterocycle is substituted with at least one group selected from -R c , -R N , -R NA and -L B -R BB , where present,
  • each ring carbon atom in -R 17 and -R B is optionally mono- or di- substituted with -R c
  • the monocyclic heterocycle is substituted with at least one group selected from -R c , and -R N , where present, or the monocyclic heterocycle is optionally substituted when -R A is -L A -R AA ,
  • a monocyclic nitrogen-containing heterocycle optionally contains one further nitrogen, oxygen or sulfur ring atom, and where a further nitrogen ring atom is present it is optionally substituted with -R N , with the exception of a further nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -R NA ; where -R 17 and -R A or -R 17 and -R B together form a bicyclic nitrogen- containing heterocycle, each ring carbon atom in -R 17 and -R A or -R 17 and -R B is optionally mono- or di-substituted with -R D ;
  • the bicyclic nitrogen-containing ring atom heterocycle optionally contains one, two or three further heteroatoms, where each heteroatom is independently selected from the group consisting of nitrogen, oxygen and sulfur, and where further nitrogen ring atoms are present, each further nitrogen ring atom is optionally substituted with -R N , with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -R NA ; where -R A and -R B together form a 5- to 10-membered monocyclic carbocycle or heterocycle, each ring carbon atom in -R A and -R B is optionally mono- or di-substituted with -R c , and a nitrogen ring atom, where present in the monocyclic heterocycle, is optionally substituted with -R N , with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring
  • each -R NA is independently -R L -R NN or -R NN:
  • each -L A - is independently a covalent bond or a linking group selected from -R L -*, -0-L AA - ⁇ -N(R 11 )-L AA -*, and -0(0)- ⁇ -*, where the asterisk indicates the point of attachment of the group -L A - to -R M ;
  • each -L B - and -L c - is independently a covalent bond or a linking group selected from -R L -*, -0-L AA -*, -OCCO ⁇ L ⁇ CR 11 )- ⁇ -*, -N(R 11 )C(0)-L AA -*, -C ⁇ 0)-L M -*, -
  • each -L N - is independently a covalent bond or a group selected from -S(0)-L AA -*, -S ⁇ -L ⁇ -*, -C(0)-L AA - * and -C(0)N(R 1 )-L AA -*, where the asterisk indicates the point of attachment of the group -L N - to -R NN ; and each -L ⁇ - is independently a covalent bond or -R 1 -; and each -R L - is independently selected from C1-12 alkylene, C2-12 heteroalkylene, C3-10
  • each -R 13 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl;
  • each -R 1 1 is independently hydrogen or C1-4 alkyl
  • -R 8 is hydrogen or methyl, and pharmaceutically acceptable salts, protected forms, solvates and hydrates thereof, such as pharmaceutically acceptable salts, and hydrates thereof.
  • -X- is -C(O)-.
  • the carbon atom in R 15 that is a to the group -X- is part of a methine (-CH-) group i.e. -R A is not hydrogen.
  • the carbon atom in R 15 that is ⁇ to the group -X- is part of a methine (-CH-) group i.e. -R B is not hydrogen.
  • the carbon atom in R 15 that is ⁇ to the group -X- is part of a methylene group.
  • -R B is hydrogen.
  • the compound is in salt form, for example the compound is an acetate salt.
  • the compound is in protected from, for example where amino and hydroxy I functionality is protected.
  • Polymyxin B nonapeptide has the structure shown below: H 2 N-Thr 2 -Dab-Dab 4 -Dab-D-Phe-Leu-Dab-Dab-Thr 10 where positions 2, 4 and 10 are indicated (with reference to the numbering system used for the Polymyxin B deca peptide), and the amino acid residues are in the
  • the compounds of the invention are derivatives of polymyxin B nonapeptide , where (i) the N terminal amino group, -Nh , is replaced with the group -NH-A-X-R 6 or -NH-X-R 15 as described herein and optionally (ii) the amino acid residues at 2, 3, 6, 7 and 10 positions are substituted with another amino acid residue.
  • the compounds of the invention are represented by the formula (III) where the amino acids at positions 2, 3. 6, 7 or 10 are determined by the nature of the groups R 8 , R 4 , R 1 , R 2 and R 3 respectively.
  • Compounds of the invention, which include the variants described above, are biologically active.
  • a variant of the compound is a compound in which one or more, for example, from 1 to 5, such as 1. 2. 3 or 4 amino acids are substituted by another amino acid.
  • the amino acid may be at a position selected from positions 2, 3, 6. 7 or 10 (referring to the numbering of residues used in polymyxin B).
  • the substitution may be for another amino acid or for a stereoisomer.
  • -Q- is a covalent bond.
  • -Q- is -CH(R B )-.
  • -R B may be a group -L A -R BB , or -R B together with -R 17 may form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle, as described in further detail below.
  • the group -Q- is preferably a covalent bond.
  • -Q- is -CH(R B )-, and forms part of a nitrogen-containing heterocycle.
  • -R B may be hydrogen.
  • -R 16 Is hydrogen
  • -R 16 is C1-4 alkyl, such as methyl, ethyl or propyl, such as methyl.
  • -R 17 is hydrogen
  • -R 17 is C1-4 alkyl, such as methyl, ethyl or propyl, such as methyl.
  • -R 17 and -R A together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle.
  • -R 17 and -R B together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle. This is discussed in further detail below.
  • -R 16 is not ethyl when -R 17 is hydrogen, methyl or ethyl.
  • -R 16 is not methyl when -R 17 is hydrogen, methyl or ethyl. In one embodiment, -R 16 is hydrogen and -R 17 is hydrogen.
  • -NR 16 R 17 is not a guanidine group.
  • Nitrogen-Containing Heterocycle The groups -R 17 and -R A may, together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle. Similarly, -R 17 and -R B may, together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle.
  • the nitrogen in the nitrogen-containing heterocycle refers to the nitrogen atom in -N(R 16 )-.
  • the nitrogen-containing heterocycle may be a monocyclic or bicyciic nitrogen-containing heterocycle. A bicyciic nitrogen-containing heterocycle has two fused rings.
  • the nitrogen-containing heterocycle contains a total of 5 to 10 ring atoms.
  • the nitrogen-containing heterocycle is monocyclic it may have 5 to 7 ring atoms, for example 5 to 6, such as 6, ring atoms.
  • the nitrogen-containing heterocycle is bicyciic it may have 8 to 10 ring atoms, such as 9 to 10, such as 10, ring atoms.
  • Each ring in the bicyciic heterocycle may have 5 to 7 ring atoms, for example 5 or 6, such as 6, ring atoms.
  • one ring may be aromatic or partially unsaturated.
  • the ring that is formed together with the carbon atoms a and ⁇ to the group -X- (the first ring) is not aromatic. It is the second ring, which is the ring fused to the first, that may be aromatic.
  • the first ring is saturated, except for the carbon ring atoms that are shared with the second ring (bridge atoms), which may be may be part of the aromatic ring system of the second ring, for example.
  • each carbon ring atom in -R 17 and -R A or each carbon ring atom in -R 17 and -R B is optionally mono- or di-substituted with -R c .
  • each carbon ring atom in -R 17 and -R A or each carbon ring atom in -R 17 and -R B is optionally mono- or di-substituted with -R D , as appropriate.
  • a carbon ring atom may be unsubstituted or mono-substituted with -R D if that carbon ring atom is part of an aromatic ring system, or is part of an unsaturated bond.
  • the group -R D includes the group -R c .
  • each carbon ring atom in the second ring is optionally mono-or di-substituted with -R D and each carbon ring atom in the first ring in is optionally mono-or di-substituted with -R c .
  • the nitrogen-containing heterocycle is a monocyclic nitrogen-containing heterocycle.
  • the nitrogen-containing heterocycle is a bicyclic nitrogen-containing heterocycle.
  • one carbon ring atom in the nitrogen-containing heterocycle is mono- or di-substituted, such as mono-substituted, with -R c or substituted with -L B -R BB , where present, for example mono-substituted with -R c .
  • one carbon ring atom in -R 17 and -R A or -R 17 and -R B is mono- or di-substituted, such as mono-substituted, with - R c , for example -L A -R CC .
  • the remaining carbon atoms in the nitrogen-containing heterocycle are unsubstituted. This embodiment is preferred when the nitrogen-containing heterocycle is monocyclic.
  • each carbon ring atom in the nitrogen- containing heterocycle may be unsubstituted.
  • one carbon ring atom in the nitrogen-containing heterocycle may be mono- or di-substituted, such as mono-substituted, with -R c or -L B -R BB , such as with -R c .
  • the nitrogen heterocycle is bicyclic one carbon ring atom in -R 17 and -R A or -R 17 and -R B is mono- or di- substituted, such as mono-substituted, with -R c , for example -L A -R CC .
  • the remaining carbon atoms in the nitrogen-containing heterocycle are unsubstituted.
  • the nitrogen-containing heterocycle may contain further hetero ring atoms independently selected from nitrogen, oxygen and sulfur. Where the nitrogen-containing heterocycle is a monocyclic, the heterocycle optionally contains one further nitrogen, oxygen or sulfur ring atom. Where the nitrogen-containing heterocycle is a bicyclic nitrogen-containing
  • the heterocycle optionally contains one, two or three further heteroatoms, where each heteroatom is independently selected from the group consisting of nitrogen, oxygen and sulfur.
  • the further heteroatoms atoms may be provided in the first or second rings, such as the first ring.
  • heteroatom is nitrogen.
  • one further heteroatom is provided, such as one further nitrogen heteroatom.
  • the nitrogen-containing heterocycle does not contain a further heteroatom.
  • heteroatoms are provided in a ring, they are not separated by an unsubstituted methylene group (-CH 2 -) or a mono-substituted methylene group (e.g. -CH(R C )-), and optionally they are not separated by a di-substituted methylene group (e.g. -C(R C )2-).
  • the ring atom may be provided as a group -NH-, and the nitrogen atom may be optionally substituted with -R N or -R NA , as appropriate.
  • a further nitrogen ring atom may be unsubstituted if it is part of an aromatic ring system, or is part of an unsaturated bond.
  • the sulfur ring atom may be provided as -S-, -S(O)- or -S(0) 2 -, such as -S-.
  • Each further nitrogen ring atom is optionally substituted with a group -R N , as appropriate, with the exception of a further nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -R NA .
  • This is shown schematically below for two exemplary R 15 -X- groups comprising monocyclic heterocycles containing a further nitrogen ring atom:
  • the ring system on the right has a nitrogen ring atom that is connected to the carbon atom that is a to the group -X-.
  • a nitrogen atom is optionally substituted with -R NA , and is shown substituted with -R NA .
  • the ring system on the left has a nitrogen ring atom that is not connected to the carbon atom that is a to the group -X- (it is attached to a carbon ⁇ to the group -X-).
  • Such a nitrogen atom is optionally substituted with -R N , and is shown substituted with -R N .
  • the carbon ring atoms are shown to be unsubstituted.
  • carbon ring atoms that are present in -R 17 and -R A are optionally mono- or di-substituted.
  • a nitrogen atom in the aromatic ring may not be substituted with a group -R N , as appropriate.
  • a further nitrogen ring atom is substituted with -R N or -R NA , as appropriate, each carbon ring atom in the nitrogen-containing heterocycle may be unsubstituted.
  • -R 1 and -R A together form a monocyclic nitrogen-containing heterocycle, the heterocycle is substituted with at least one group selected from -R c , and -R N , -R NA and -L B -R BB i.e.
  • the nitrogen-containing heterocycle is monocyclic and does not contain a further nitrogen atom
  • at least one carbon ring atom must be substituted with -R c or -L B -R BB , where present.
  • the nitrogen-containing heterocycle is monocyclic and contains a further nitrogen atom, and that nitrogen atom is unsubstituted
  • at least one carbon ring atom must be substituted with -R c or -L B -R BB , where present. If a further nitrogen atom in the monocyclic nitrogen-containing heterocycle is substituted with a group -R N or -R NA , the carbon ring atoms may be
  • the heterocycle is substituted with at least one group selected from -R c , and -R N , where present.
  • the heterocycle is optionally substituted if -R A is -L R ⁇ .
  • the monocyclic nitrogen-containing heterocycle is unsubstituted when the group -R A is -L A -
  • the monocyclic nitrogen-containing heterocycle must be substituted with at least one group selected from -R c , and -R N , where present.
  • the nitrogen- containing heterocycle is monocyclic and does not contain a further nitrogen atom, at least one carbon ring atom must be substituted with -R c .
  • the nitrogen-containing heterocycle is monocyclic and contains a further nitrogen atom, and that nitrogen atom is unsubstituted, at least one carbon ring atom must be substituted with -R c .
  • the carbon ring atoms may be unsubstituted or optionally mono- or di- substituted.
  • each further nitrogen ring atom may be unsubstituted.
  • one further nitrogen ring atom may be substituted with a group -R N , except where the further nitrogen ring atom is connected to the carbon that is a to the group -X-, that further nitrogen ring atom is substituted with a group -R NA .
  • a monocyclic nitrogen-containing heterocycle is mono-substituted with -R c .
  • one carbon ring atom in the group -R 17 and -R A or -R 17 and -R B is
  • a monocyclic nitrogen-containing heterocycle containing a further nitrogen ring atom is mono-substituted with a group -R c , -R N or -R NA , for example mono-substituted with a group -R N or -R NA or mono-substituted with a group -R c .
  • one ring atom in the group -R 7 and -R A or -R 17 and -R B is mono-substituted.
  • the nitrogen-containing heterocycie may be selected from the group consisting of pyrrolidine, piperidine, piperazine, 1.4-diazepine, indoline, 1 ,2,3,4-tetrahydroquinoline, 1 ,2,3,4-tetrahydroisoquinoline, 1 ,2,3,4-tetrahydroquinoxaline, 1 ,2,3,4,6,7.8,8a- octahydropyrrolo[1 ,2-a]pyrazine, 1.2.3,4-tetrahydropyrrolo[1 ,2-a]pyrazine, 5.6,7,8-tetrahydro- 1 ,6-naphthyridine and 1 ,2,3,4-tetrahydro-2,6-naphthyridine.
  • the aromatic ring where present, is provided as the second ring.
  • the monocyclic nitrogen-containing heterocycles pyrrolidine, piperidine, piperazine, and 1 ,4-diazepine are substituted as discussed above.
  • 1.2,3,4-tetrahydroisoquinoline and 1 ,2,3,4-tetrahydroquinoxaline may be substituted or unsubstituted, as discussed above.
  • a nitrogen-containing heterocycie may be selected from the group consisting of pyrrolidine, piperidine, piperazine, and 1 ,4-diazepine.
  • a nitrogen-containing heterocycie is selected from pyrrolidine, piperidine and piperazine.
  • a bicyclic nitrogen-containing heterocycie has a first ring selected from pyrrolidine, piperidine and piperazine fused to a second ring, which may be an aromatic ring.
  • a second ring which may be an aromatic ring.
  • the second ring include cyclohexane, benzene and pyridine ring
  • the groups -R 17 and -R A together form a nitrogen heterocycie when -CD- is a covalent bond.
  • the group -NR 16 - is located on a carbon atom that is ⁇ to the group -X-.
  • the groups -R 17 and -R A together form a nitrogen heterocycie when -Q- is not a covalent bond.
  • the group -NR 16 - is located on a carbon atom that is ⁇ to the group -X-.
  • -R 17 and -R A are selected from * -CH(R c1 )CH(R c1 )CH(R C1 )-,
  • -R A and -R B together form a 5- to 10-membered carbocycle or heterocycle.
  • -Q- is not a covalent bond.
  • the carbocycle or heterocycle may be substituted or unsubstituted.
  • a carbocycle or a heterocycle may be monocyclic or bicyclic.
  • a bicyclic carbocycle or a heterocycle has two fused rings.
  • the carbocycle or a heterocycle contains a total of 5 to 10 ring atoms.
  • the carbocycle or heterocycle is monocyclic it may have 5 to 7 ring atoms, for example 5 to 6, such as 6, ring atoms.
  • the carbocycle or heterocycle is bicyclic it may have 8 to 10 ring atoms, such as 9 to 10, such as 10, ring atoms.
  • Each ring in the bicyclic system may have 5 to 7 ring atoms, for example 5 or 6, such as 6, ring atoms.
  • one ring may be aromatic or partially unsaturated.
  • the ring that is formed together with the carbon atoms a and ⁇ to the group -X- (the first ring) is not aromatic. It is the second ring, which is the ring fused to the first, that may be aromatic. The first ring is saturated, except for the carbon ring atoms that are shared with the second ring (bridge atoms), which may be may be part of the aromatic ring system of the second ring.
  • a bicyclic heterocycle is a heterocycle having a heteroatom, such as N, S, or O in either the first or second ring.
  • a heteroatom is present in the first ring. In one embodiment, a heteroatom is present in the second ring.
  • the heterocycle includes one or more heteroatoms independently selected from N, S, and O.
  • heterocycle includes one or two, such as one heteroatom.
  • the heteroatom is nitrogen.
  • one heteroatom present such as one nitrogen heteroatom.
  • each carbon ring atom in -R A and -R B is optionally mono- or di-substituted with -R c .
  • each carbon ring atom in -R A and -R B is optionally mono- or di-substituted with -R D , which includes -R c .
  • the ring atom may be provided as a group -NH-, and the nitrogen atom may be optionally substituted with -R N or -R NA , as appropriate.
  • a further nitrogen ring atom may be unsubstituted if it is part of an aromatic ring system, or is part of an unsaturated bond.
  • the sulfur ring atom may be provided as -S-, -S(O)- or -S(0)2-, such as -S-.
  • one carbon ring atom in the carbocycle or heterocycle is mono- or di-substituted, such as mono-substituted, with -R c or -R D , where appropriate.
  • the remaining carbon atoms in the carbocycle or heterocycle may be unsubstituted.
  • the heterocycle has a nitrogen ring atom and that atom is optionally substituted with -R N , with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -R NA .
  • a nitrogen ring atom is present in the heterocycle, that ring atom may be substituted.
  • the remaining carbon atoms in the carbocycle or heterocycle may be unsubstituted. This embodiment is preferred when the heterocycle is monocyclic.
  • a nitrogen atom in the aromatic ring may be substituted with a group - R N , as appropriate.
  • a monocyclic carbocycle is selected from cyclohexane and
  • a monocyclic heterocycle is selected from pyrrolidine, tetrahydrofuran, tetrahydrothiophene, piperidine, piperazine, 1 ,4-dioxane, morpholine, thiomorpholine and 1 ,4-diazepine, which may be substituted as discussed above.
  • a monocyclic carbocycle is selected from indane and tetralin.
  • a bicyclic heterocycle is selected from indoline,
  • the group -R 15 together with -X- may be regarded as an N terminal substituent group in the compounds of formula (III).
  • -R 15 contains an amino group which may be a group -NR 16 R 17 , or a group -NR 16 - where the nitrogen is present as a ring atom in a nitrogen-containing heterocycle.
  • the nitrogen group -NR 16 R 17 must be bonded to one methylene group (i.e. a group -CH2-).
  • -R 15 must contain a group -CH2NR 16 R 17 .
  • the nitrogen atom in -NR 16 - is bonded to one neighboring carbon atom that is part of a methylene group. This is a requirement for the group -R 15 .
  • the other neighboring ring carbon atom is not necessarily part of a methylene group (it may be a methylene or methine group).
  • the nitrogen atom in -NR 16 - is bonded to two ring methylene groups (i.e. both neighboring ring carbon atoms are provided in methylene groups).
  • the nitrogen atom in - NR 16 - is bonded to a carbon ring atom that is part of a methylene group and a carbon ring atom that is part of a methylene or methine group.
  • -R 15 is selected from the groups listed below.
  • the groups shown below include groups where -R 1 7 and -R A together form a nitrogen-containing heterocycle.
  • -R C1 is hydrogen or -R c ;
  • -R N1 is hydrogen or -R NA ;
  • -R D1 is hydrogen or -R D ;
  • -R A is hydrogen or -LAR ⁇ ;
  • -R B is hydrogen or -L B -R BB ; and
  • -R 16 is independently hydrogen or C 1 -4 alkyl;
  • -R 17 is independently hydrogen or C1.4 alkyl; or -NR 16 R 17 is a guanidine group.
  • -Q- is -CH(R B )- one or both of -R A and -R B is not hydrogen.
  • the nitrogen- containing heterocycle is monocyclic, it should be substituted with at least one group selected from -R c , and -L B -R BB , -R NA and -R N .
  • -R 15 is selected from the roup consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the roup consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the roup cons
  • -R 15 is selected from the group consisting of:
  • -R 15 is selected from the group consisting of:
  • -R 15 is:
  • -R 15 is:
  • -R 15 is:
  • the structures shown above include examples where -R 16 contains a nitrogen-containing heterocycie. These are compounds where the groups -R 17 and -R A , together with the carbon atoms to which they are attached, form a nitrogen heterocycie.
  • the nitrogen heterocycles shown above are monocyclic nitrogen heterocycles.
  • Each carbon ring atom in the group -R 17 and -R A may be substituted with -R C1 .
  • -R C1 is hydrogen, the carbon ring atom is unsubstituted.
  • a nitrogen ring atom in the group -R 17 and -R A , where present, is substituted with -R N1 .
  • -R N1 is hydrogen, the nitrogen ring atom is unsubstituted.
  • the nitrogen-containing heterocycie contains a further nitrogen atom
  • the further nitrogen atom is substituted with -R N or -R NA , as appropriate.
  • the ring carbon atoms may be unsubstituted.
  • one of the carbon ring atoms is substituted with -R c or -L B -R BB , and preferably one of the carbon ring atoms group -R 17 and -R A is substituted with -R c .
  • the compounds of the invention also include compounds where -R 17 and -R A , together with the carbon atoms to which they are attached, form a bicyclic nitrogen heterocycie.
  • -R 15 is selected from:
  • -R 15 is selected from:
  • -R 15 is selected from:
  • -R A and -R B may together form a carbocycle or a heterocycle.
  • the ring atoms of the carbocycle or heterocycle may be optionally substituted.
  • a carbon ring atom may be optionally mono- or di-substituted with -R c .
  • a nitrogen ring atom, where present, may be optionally substituted with -R N , except that a nitrogen ring atom that is connected to the carbon that is a to the group -X- is optionally substituted with -R NA .
  • the nitrogen-containing carbocycle heterocycle is monocyclic, it is optionally substituted with at least one group selected from -R c , and -R NA and -R N .
  • -R 16 is selected fro
  • -R A is not hydrogen. In one embodiment, -R A is -L A -R AA . In one embodiment, -R A is -R AA . In these embodiments, -R B , if present, may be hydrogen. In one embodiment, where -R A is not hydrogen, for example where -R A is -LA-R ⁇ or -R A and -R 17 together form a nitrogen-containing heterocycle, -R 15 is an amino-containing group:
  • -R A is -L R** it is noted that this group does not encompass a substituent containing the group -C(0)N(R 11 )- * , where the asterisk indicates the point of attachment to the carbon that is a to the group -X-.
  • the inventors have found that where the group -C(0)N(R 11 )- * is present, biological activity is reduced.
  • -R A and -R 17 together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle.
  • -R A and -R B together form a 5- to 10-membered carbocycle or heterocycle.
  • -Q- is not a covalent bond.
  • -R A is not -NHEt or -NE , for example where R 15 -X- is an N terminal substituent to Polymyxin B nonapeptide (PMBN).
  • -R A is not -NHR PA or -N(R PA )2, where each -R PA is C1-10 alkyl, such as Cs-10 alkyl, such as Ci-8 alkyl, such as C1-1 alkyl, such as C1-2 alkyl, for example where R 15 -X- is an N terminal substituent to Polymyxin B nonapeptide (PMBN).
  • PMBN Polymyxin B nonapeptide
  • -R A is not a group having an oxygen atom attached to the carbon that is a to the group -X-. In one embodiment, -R A is not a group having a nitrogen atom attached to the carbon that is a to the group -X-.
  • the definitions for the group -LA-R ⁇ may be construed accordingly.
  • -R B where present, is hydrogen.
  • -Q- is a covalent bond and -R B is accordingly absent.
  • -R B is -L A -R BB . In one embodiment, -R B is -R BB . In these embodiments, -R A may be hydrogen. In one embodiment, -R B is not C3-10 cycloalkyl, for example is not cyclohexyl.
  • -R B and -R 17 together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle. In one embodiment, -R A and -R B together form a 5- to 10-membered carbocycle or heterocycle.
  • -Q- is not a covalent bond.
  • each carbon ring atom in -R B and -R 1 / is optionally substituted with -R c
  • each nitrogen ring atom in -R B and -R 17 is optionally substituted with -R N .
  • one of -R A and -R B is hydrogen.
  • the other of -R A and -R B is therefore not hydrogen.
  • the groups -R A and -R 17 or -R B and -R 17 may together form a 5- to 10-membered nitrogen- containing monocyclic or bicyclic heterocycle, and -R A and -R B may together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or together form a 5- to 10-monocyclic or bicyclic heterocycle.
  • the ring atoms that are present in the nitrogen-containing heterocycle and the carbocycle or heterocycle may be substituted or unsubstituted as described herein.
  • the nitrogen-containing heterocycle includes ring atoms that are part of -R A and -R 17 or -R B and -R 17 .
  • -R A and -R or -R B and -R 17 form a nitrogen-containing monocyclic or bicyclic heterocycle
  • each carbon ring atom in the group -R A and -R 17 or the group -R B and -R 17 may be optionally substituted with -R c .
  • These carbon ring atoms may be mono- or di-substituted with -R c .
  • each carbon ring atom is optionally mono- substituted with -R c .
  • the substituent may be present as a substituent to a ring atom that is part of -R A and -R 17 or -R B and -R 17 .
  • a group -R c , -R N or -R NA is present.
  • the substituent may be present at the carbon to the group -X- i.e. -L B -R BB is present.
  • the nitrogen-containing heterocycle may contain further nitrogen ring atoms. Each further nitrogen ring atom may be optionally substituted with -R N , as appropriate. However, where the further nitrogen atom is bonded to the carbon that is a to the group -X-, that ring nitrogen atom is optionally substituted with -R NA .
  • -R A and -R B together form a 5- to 10-membered monocyclic or bicyclic carbocycle or heterocycle.
  • each ring carbon atom in -R A and -R B is optionally mono- or di-substituted with -R c .
  • These carbon ring atoms may be mono- or di-substituted with -R c .
  • each carbon ring atom is optionally mono- substituted with -R c .
  • each ring carbon atom in -R A and -R B is optionally mono- or di-substituted with -R D .
  • These carbon ring atoms may be mono- or di-substituted with -R D .
  • a 5- to 10-membered monocyclic or bicyclic heterocycle may contain a nitrogen ring atom.
  • Each nitrogen ring atom may be optionally substituted with -R N , as appropriate. However, where the further nitrogen atom is bonded to the carbon that is a to the group -X-, that ring nitrogen atom is optionally substituted with -R NA .
  • a ring carbon atom that is connected to the nitrogen atom in -N(R 16 )- is not substituted with oxo.
  • a carbon ring atom is substituted with oxo it may be joined to a further nitrogen ring atom (where such is present) to from an amide group.
  • a further nitrogen atom may be connected to the carbon atom that is a to the group -X-.
  • the inventors understand that where an amide group is present within a nitrogen-containing heterocycle as a substituent to the carbon ⁇ to the group -X-, biological activity is not reduced.
  • a ring carbon atom is connected to a further nitrogen ring atom that is connected to the carbon atom that is a to the group -X-, that ring carbon atom is not substituted with oxo.
  • a carbon ring atom is substituted with oxo it may be joined to a further oxygen ring atom (where such is present) and an ester group may be formed.
  • the nitrogen-containing heterocycle does not include a ring amide, carbamate, urea or ester group.
  • a further nitrogen ring atom connected to the carbon that is a to the group -X- is not part of an amide, carbamate or urea group.
  • a further oxygen ring atom connected to the carbon that is a to the group -X- is not part of a carbamate or ester group.
  • -R 17 and -R A form a monocyclic nitrogen-containing heterocycle, one ring atom
  • the monocyclic nitrogen heterocycle must have a substituent group present on a carbon ring atom or further nitrogen ring atom, where present.
  • at least one group -R c , -R N , -R NA or -L B -R BB must be present as a substituent to the nitrogen-containing heterocycle.
  • at least one group -R c , -R N and -R NA must be present as a substituent to the nitrogen-containing heterocycle.
  • -R 17 and -R A form a monocyclic nitrogen-containing heterocycie
  • one or two ring atoms in -R 17 and -R A are substituted. The remaining ring atoms in -R 17 and -R A are unsubstituted.
  • one ring atom in -R 17 and -R A is substituted.
  • R 17 and -R A form a monocyclic nitrogen-containing heterocycie
  • one carbon ring atom in -R 1 and -R A is substituted with -R c , and the remaining ring atom in -R 17 and -R A are unsubstituted.
  • R 17 and -R A form a monocyclic nitrogen-containing heterocycie
  • the heterocycie has a further nitrogen ring atom
  • the further nitrogen is substituted with -R N or -R NA , as appropriate, and the remaining ring atoms in -R 17 and -R A are unsubstituted.
  • R 17 and -R A form a monocyclic nitrogen-containing heterocycie
  • the heterocycie has a further nitrogen ring atom
  • one carbon ring atom in -R 17 and -R A is substituted with -R c , and the remaining ring atoms in -R 1 and -R A are unsubstituted.
  • -R 17 and -R B form a monocyclic nitrogen heterocycie
  • the ring atoms in the ring (formed together with the carbon atom ⁇ to the group -X-) need not be substituted.
  • the group -R A is hydrogen
  • the monocyclic nitrogen heterocycie must have a substituent group present on a carbon ring atom or further nitrogen ring atom, where present.
  • the group -R A is not hydrogen, then the carbon ring atoms or further nitrogen ring atom, where present, need not be substituted.
  • -R 17 and -R B form a monocyclic nitrogen-containing heterocycie
  • one or two ring atoms in -R 17 and -R B are substituted.
  • the remaining ring atoms in -R 1 and -R B are unsubstituted.
  • one ring atoms in -R 17 and -R B is substituted.
  • -R A may be hydrogen.
  • R 17 and -R B form a monocyclic nitrogen-containing heterocycie
  • one carbon ring atom in -R 17 and -R B is substituted with -R c , and the remaining ring atoms in
  • R 17 and -R B form a monocyclic nitrogen-containing heterocycie, and the heterocycie has a further nitrogen ring atom, the further nitrogen is substituted with
  • R 17 and -R B form a monocyclic nitrogen-containing heterocycie, and the heterocycie has a further nitrogen ring atom
  • one carbon ring atom in -R 17 and -R B is substituted with -R c , and the remaining ring atoms in -R 17 and -R B are unsubstituted.
  • a bicyclic nitrogen-containing heterocycie may be unsubstituted.
  • the second fused ring may be regarded as a substituent to the first ring.
  • R 17 and -R A form a bicyclic nitrogen-containing heterocycie
  • one carbon ring atom in -R 17 and -R A is substituted with -R D , and the remaining ring atoms in -R 17 and -R A are unsubstituted.
  • R 17 and -R A form a bicyclic nitrogen-containing heterocycle
  • the heterocycle has a further nitrogen ring atom
  • the further nitrogen is substituted with -R N or -R NA , as appropriate, and the remaining ring atoms in -R 17 and -R A are unsubstituted.
  • R 17 and -R A form a bicyclic nitrogen-containing heterocycle, and the heterocycle has a further nitrogen ring atom
  • one carbon ring atom in -R 17 and -R A is substituted with -R D , and the remaining ring atoms in -R 17 and -R A are unsubstituted.
  • a group -R D is -R c when it is provided as a substituent on the first ring of a bicyclic nitrogen-containing heterocycle.
  • each -R D is independently selected from -R c , halo, -OH, and -NH2. In one embodiment, each -R D is independently selected from -R c and halo.
  • each -R D is independently -R c .
  • each -R D is independently -L c -R cc .
  • a bicyclic nitrogen-containing heterocycle contains a first ring and a second ring.
  • the first ring is the nitrogen heterocycle including the carbon atom that is ⁇ to the group -X-.
  • each carbon ring atom in -R 17 and -R A that is part of the first ring is optionally mono- or di-substituted with -R c .
  • the second ring is the ring fused to the first ring.
  • Each carbon ring atom in -R 7 and -R A that is part of the second ring is optionally mono- or di-substituted with -R D . - ⁇
  • the group -L A - may be a covalent bond.
  • -L A - may be a linking group.
  • An asterisk is used to indicate the point at which the group point of attachment of the group -L A - to -R AA .
  • the remaining attachment point connects to the carbon that is a to the group -X-.
  • -L A - is not a group -N(R 11 )C(0)- * where the asterisk is the point of attachment to -R AA .
  • the inventors have found that such groups have a poor biological activity, as discussed above.
  • the linking group is selected from -R 1 - * , -O-L ⁇ - * , -N(R 11 )-L AA - * , and -0(0)- ⁇ - * .
  • the linking group is selected from -R' - * , -O-L ⁇ - * , and -C(0)-L AA - * .
  • the linking group is selected from -R L - * , -N(R 11 )-L AA - * , and -C(0)-L AA - In one embodiment, the linking group is selected from -R 1 - * and -0(0)- ⁇ - * .
  • the linking group is selected from -R L - * , -O-L ⁇ - * , and -N(R 11 )-L AA - * . In one embodiment, the linking group is selected from -R L - * and -0-L AA - * . In one embodiment, the linking group is -R L -*. -L B - The group -L B - may be a covalent bond.
  • Alternatively -L B - may be a linking group.
  • An asterisk is used to indicate the point at which the group point of attachment of the group -L B - to -R BB .
  • the remaining attachment point connects to the carbon that is ⁇ to the group -X- (i.e. the carbon atom in -CH(R B )-).
  • the linking group is selected from R 1 -*, -O-L ⁇ -*, -00(0)- ⁇ -*, -N(R 1 1 )-L AA -*, -C(0)-L AA -*, and -0(0)0-1./ -*.
  • the linking group is selected from -R 1 -*, -O-L ⁇ -*, -N(R 1 1 )-L AA -*,
  • the linking group is selected from -R 1 -*, -0-L AA -*, -N(R 1 1 )-L AA -*,
  • the linking group is selected from -R L -*, -O-L ⁇ -*, and -N(R 11 )-L AA -*. In one embodiment, the linking group is -R 1 -*. Additionally or alternatively, the linking group is selected from -N(R 11 )S(0)-L AA -* and -N(R 1 1 )S(0) 2 -L AA -*.
  • the linking group is -N(R 1 1 )S(0)2-L AA -*.
  • the linking group is -N(R 11 )S(0)2-*. Additionally or alternatively, the linking group is selected from -S(0)N(R 1 1 )-L AA -*, and
  • the linking group is -S(0)N(R , 1 )-L AA -*.
  • the linking group is -S(0)2N(R 11 )-L AA -*. -L c -
  • the group -L c - may be a covalent bond.
  • Alternatively -L c - may be a linking group.
  • An asterisk is used to indicate the point at which the group point of attachment of the group -L c - to -R cc . Thus, the remaining attachment point connects to the carbon ring atom.
  • the linking group is selected from R 1 -*, -O-L ⁇ -*, -OC(0)-L AA -*,-N(R 1 1 )-
  • the linking group is selected from -R' -*, -O-L**-*, -N(R 1 1 )-L AA -*, -C(0)-L M -*, -C(0)0-L AA -*, and -C(0)N(R 11 )-L AA -*.
  • the linking group is selected from -R 1 -*, -O-L ⁇ -*, -N(R 1 1 )-L AA -*,
  • the linking group is selected from -R L - * , -O-L ⁇ - * , and -N(R 11 )-L AA - * . In one embodiment, the linking group is -R 1 - * .
  • the linking group is selected from -N(R 11 )S(0)-L AA - * and -N(R 11 )S(0) 2 -L AA - * .
  • the linking group is -N(R 11 )S(0)2-L AA - * .
  • the linking group is -N(R 11 )S(0)2-*.
  • the linking group is selected from -S(0)N(R 11 )-L AA - * , and -S(0) 2 N(R 11 )-L AA - * .
  • the linking group is -S(0)N(R 11 )-L AA - * .
  • the linking group is -S(0)2N(R 11 )-L AA - * .
  • a group -L AA - is independently a covalent bond.
  • a group -L AA - is independently -R L .
  • a group -L N - is independently a covalent bond.
  • a group -L N - is a linking group.
  • An asterisk is used to indicate the point of attachment of the group -L N - to -R NN .
  • the remaining attachment point connects to the nitrogen ring atom.
  • the linking group may be independently selected from -S(0)-L AA - * , -S ⁇ -L ⁇ - * , -0(0)- ⁇ - * and -C(0)N(R , 1 )-L AA - * .
  • the linking groups may together with the nitrogen atom to which they are attached, form sulfinamide, sulfonamide, amide and urea functionality respectively.
  • the linking group is independently selected from -S(0)2-L AA - * ,
  • linking is independently selected from -S(0)2-L AA - * and
  • the group -L N - is present only as a substituent to a further ring nitrogen atom that is not connected to the carbon that is a to the group -X-. Where a further ring nitrogen atom is connected to the carbon that is a to the group -X-, it is optionally substituted with -R L -R NN .
  • the group -R' -R NN does not allow for sulfinamide, sulfonamide, amide and urea groups connected to the carbon that is a to the group -X-. The presence of sulfinamide, sulfonamide, amide and urea functionality is believed to be tolerated at other ring positions.
  • each -R L - is independently selected from C1-12 alkylene, C2-12 heteroalkyiene, C3-10 cycloalkylene and C5-10 heterocyclylene.
  • -L ⁇ - is connected to a group C1-12 alkyl
  • -R' - is not C1-12 alkylene
  • -L ⁇ - is connected to a group C1-12 alkyl
  • -R L - is not C1-12 alkylene and it is not C2-12 heteroaikylene.
  • -R L - is a heteroalkyiene it may be connected to -R AA , -R BB , -R cc , or -R NN via a heteroatom of the heteroalkyiene group, such as N, O or S, where present, or a carbon atom of the heteroalkyiene group.
  • the other point of connection is made via a carbon atom of the heteroalkyiene group, for example where the heteroaikylene is attached to a carbon atom or a heteroatom, such as N, O or S.
  • the other point of connection may be made via a heteroatom of the heteroaikylene group, for example where the heteroalkyiene is attached to a carbon atom.
  • it is preferred that the other point of connection is made via a carbon atom of the heteroaikylene group, particularly where -R L - is present in a group -L AA -.
  • -R' - is a heterocyclylene it may be connected to -R M , -R BB , -R cc , or -R NN via a ring nitrogen heteroatom of the heterocyclylene group, where present, or a carbon ring atom of the heterocyclylene group.
  • the other point of connection is made via a ring carbon atom of the heterocyclylene group, for example where the heterocyclylene is attached to a carbon atom or a heteroatom, such as N, O or S.
  • the other point of connection may be made via a ring nitrogen heteroatom of the heterocyclylene group, for example where the
  • heterocyclylene is attached to a carbon atom.
  • a group -R L - is independently selected from C1 -12 alkylene, and C2-12 heteroalkyiene.
  • a group -R 1 - is independently selected from C1-12 alkylene and
  • a group -R 1 - is independently C1-12 alkylene.
  • the group -R L - may be substituted with one or more groups -R s .
  • each C1-12 alkylene, C2-12 heteroaikylene, C3-10 cycloalkylene and C5-10 heterocyclylene is optionally substituted with one or more groups -R s .
  • the specified groups may be unsubstituted or mono- substituted.
  • the group -R s may be present as a substituent to a carbon atom.
  • a carbon atom may be optionally mono- or di-substituted with -R s .
  • a nitrogen atom is present in a group, such as in a heterocyclylene group or a heteroaikylene group, that nitrogen atom may be optionally substituted with a group -R 12 .
  • a group -R L - is unsubstituted.
  • a C1-12 alkylene group is selected from C1-6 alkylene, C1-4 alkylene,
  • an alkylene group is linear.
  • a C1-12 alkylene group is selected from -CH2-, -CH2CH2-, and -CH(CH3)-. In one embodiment, a C1-12 alkylene group is -CH2-. for example when it is connected to a cycloalkyl, heterocyclyl, or aryl group.
  • a C2-12 heteroalkylene group is selected from C2-6 heteroalkylene, and C2-4 heteroalklyene.
  • a C2-12 heteroalkylene group is selected from -CH2O- * , -CH2CH2O-*, -CH2NH-*, -CH2CH2NH-*, -CH 2 N(R 12 )- * , and -CH 2 CH 2 N(R 12 )-*, where the asterisk indicates the point of attachment to -R M , -R BB , -R cc , or -R NN .
  • heteroalkylene group may be connected to -R AA , -R BR , -R cc , or -R NN .
  • the other point of connection may be made via a carbon atom of the heteroalkylene group.
  • an S atom is present in the heteroalkylene group, it may be in the form S, S(O) or S(0) 2 .
  • the C3-10 cycloaikylene is selected from cyciopropylene, cyclopentylene and cyclohexylene. In one embodiment, the C3-10 cycloaikylene is cyclohexylene.
  • the C5-10 heterocyclylene is C 6 heterocyclylene.
  • the C5-10 heterocyclylene is selected from piperidinene, piperazinene, morpholinene and thiomorphoiinene.
  • the heterocyclylene may be connected to -R M , -R BB , -R cc , or -R NN via a ring carbon or ring nitrogen atom. The other point of connection may be made via a carbon atom of the heterocyclylene group.
  • a nitrogen atom, where present, is optionally substituted with -R 12 .
  • an S atom is present in the heterocyclylene group, it may be in the form S, S(O) or
  • Each of -R AA , -R BB , -R cc , and -R NN is independently selected from C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, and C5-12 aryl.
  • a C1-12 alkyl group is selected from Ci-r, alkyl, C1-7 alkyl, C1-4 alkyl, C2-6 alkyl, C2-1 alkyl, C3-10 alkyl, C3-7 alkyl, C4-10 alkyl and Ce-io alkyl.
  • an alkyl group is linear.
  • an alkyl group is branched. In one embodiment, the C1-12 alkyl group does not include Ce alkyl.
  • a C3-10 cycloalkyl group is C3-6 cycloalkyl or C5-6 cycloalkyl. In one embodiment, a C3-10 cycloalkyl group is cyclohexyl.
  • a C4-10 heterocyciyi group is selected from C5-10 heterocyciyi,
  • a C4-10 heterocyciyi group is selected from tetrahydrofuranyl, pyrrolidinyl, tetrahydropyranyl, morpholinyl, thiomorpholinyl, piperidinyl and piperazinyl.
  • a C4-10 heterocyciyi group is selected from tetrahydropyanyl
  • an S atom is present in a heterocyciyi group, it may be in the form S, S(O) or S(0)2.
  • a nitrogen atom, where present, is optionally substituted with -R 12 .
  • a heterocyciyi group may be connected via a ring nitrogen heteroatom atom or a ring carbon atom.
  • the heterocyciyi group is a substituent to a nitrogen atom (e.g. present in the group -R L -)
  • the heterocyciyi group is connected to that nitrogen atom via a ring carbon atom.
  • An aryl group particularly a heteroaryl group such as indole, may be connected via a ring nitrogen heteroatom atom or a ring carbon atom.
  • the heteroaryl group is a
  • the heteroaryl group is connected to that nitrogen atom via a ring carbon atom.
  • the aryl group is connected via a ring carbon atom.
  • the C5-12 aryl is selected from Ce-12 carboaryl and C5-12 heteroaryl.
  • the C5-12 aryl is selected from phenyl, pyridyl, and naphthyl, optionally together with 1 ,3-benzodioxolyl and pyridonyl.
  • the Cr > -12 carboaryl is selected from phenyl, naphthyl, chromanyl, iso- chromanyl and 1 ,3-benzodioxolyl.
  • the chromanyl, iso-chromanyl and 1 ,3-benzodioxolyl groups are connected via an aromatic ring carbon atom. Further discussion about the meaning of the term carboaryl is provided below with reference to the group -G.
  • the Ce-12 carboaryl is selected from phenyl and naphthyl,
  • the C5-12 heteroaryl is selected from C5-10 heteroaryl and C5-6 heteroaryl. In one embodiment, the C5-12 heteroaryl is selected from the group consisting of
  • heteroaryl is provided below with reference to the group -G.
  • Each C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyciyi, and C5-12 aryl group is optionally substituted with -R s at carbon and -R 12 at nitrogen, where present.
  • Each group may have one, two, three or more groups -R s .
  • a heterocyciyi group or a heteroaryl group may have one, two, three or more groups -R 12 .
  • a group is mono-subsituted.
  • a group is unsubstituted.
  • the group -R s is present as a substituent to a carbon atom.
  • a carbon atom may be optionally mono- or di-substituted with -R s .
  • nitrogen atom such as in a heterocyclyl group or a heteroaryl group, that nitrogen may be optionally substituted with a group -R 12 .
  • - M is independently selected from C1-12 a Iky I and C5-12 aryl.
  • -R M is independently C1-12 alkyl.
  • -R AA is independently C2-12 alkyl, such as C3-12 alkyl.
  • -R M is independently C5-12 aryl.
  • -R BB is independently selected from C1-12 alkyl, C4-10 heterocyclyl, and C5-12 aryl, for example when -L B - is a covalent bond, or for example when -R A is hydrogen.
  • -R BB is independently selected from C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, and C5-12 aryl, for example when -R B is a substituent to a heterocycle ring carbon atom.
  • -R BB is independently selected from C1-12 alkyl and C5-12 aryl.
  • -R BB is independently C1-12 alkyl. In one embodiment, -R BB is independently C2-12 alkyl, such as C3-12 alkyl.
  • -R BB is independently C5-12 aryl.
  • a group -R NN is independently selected from C1-12 alkyl and C5-12 aryl. In one embodiment, -R NN is independently C1-12 alkyl. In one embodiment, -R NN is independently C2-12 alkyl, such as C3-12 alkyl.
  • -R NN is independently C5-12 aryl.
  • the group -R s is an optional substituent to each C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, C5-12 aryl, C1-12 alkylene, C2-12 heteroalkylene, C3-10 cycloalkylene and C5-10 heterocyclylene group. Where a group is optionally substituted, it may be optionally substituted with one or more groups -R s . A group may be optionally mono-substituted with -R s .
  • each -R s is an optional substituent to a carbon atom.
  • a carbon atom may be mono-, di- or tri-substituted.
  • each -R s where present, is independently selected from -OH, -OR 12 , halo, -R 12 , -NHR 12 , -NR 12 R 13 , -C(0)R 12 , -COOH and -COOR 12 .
  • each -R s where present, is independently selected from -OR 12 , halo, -R 12 , -NHR 12 , -NR 12 R 13 , -C(0)R 12 , -COOH and -COOR 12 .
  • each -R s is independently selected from -OR 12 , halo, and -R 12 .
  • -R s is a substituent to an a Iky I group, -R s is not -R 12 .
  • -R s is halo it may be selected from fluoro, chloro, bromo and iodo, such as chloro and bromo, such as chloro.
  • these groups may together with the carbon to which they are attached form a C3-6 carbocycle or a C»-e heterocycle, where the carbocycle and the heterocycle are optionally substituted with one or more groups -R 2 .
  • an S atom is present in the heterocycle group, it may be in the form S, S(O) or S(0) 2 .
  • a C3-6 carbocycle is cyclopentane or cyclohexane, such as cyclohexane.
  • a C5-6 heterocycle is selected from piperidine, piperazine, morpholine, thiomorpholine, tetrahydrofuran and tetrahyd ropy ran.
  • Each -R 12 and -R 13 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl.
  • -R 12 and -R 13 are both attached to N, they may together with the N atom form a 5- or 6-membered heterocycle, such as pyrrolidine, piperazine, piperidine, thiomorpholine or morpholine.
  • the heterocyclic ring is optionally substituted with C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl.
  • a -R 12 or -R 13 group is independently C1-6 alkyl, phenyl or benzyl.
  • a -R 12 or -R 13 group is independently C1-6 alkyl. In one embodiment, the C1-6 alkyl is selected from methyl and ethyl.
  • the C1-6 haloalkyl is -CF 3 .
  • a group -R 11 is independently selected from hydrogen, methyl and ethyl. In one embodiment, -R 11 is independently hydrogen.
  • the -R 1 position corresponds to amino acid position 6 in the polymyxin compounds.
  • -R 1 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a phenylalanine residue, for example a D-phenylalanine, or a leucine residue, such as a D-leucine residue.
  • the -R 2 position corresponds to amino acid position 7 in the polymyxin compounds.
  • -R 2 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a leucine or threonine residue, such as L-leucine or L-threonine.
  • the -R 3 position corresponds to amino acid position 10 in the polymyxin compounds.
  • -R 3 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a threonine residue, such as L-threonine.
  • the -R 4 position corresponds to the side chain of the amino acid position 3 in the polymyxin compounds.
  • the group -R 4 together the carbonyl group and nitrogen alpha to the carbon to which it is attached, is an amino acid residue having an amino- or hydroxyl-containing side chain.
  • -R 4 is Ci_i alkyl, having one amino or one hydroxyl substituent.
  • -R 4 has one amino substituent.
  • -R 4 has one hydroxyl substituent.
  • the amino group may be -Nh , -NHMe or -NHEt. In one embodiment, the amino group is
  • -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is ⁇ , ⁇ -diaminobutyric acid (Dab), a serine residue, a threonine residue, a lysine residue, an ornithine residue, or ⁇ . ⁇ -diaminopropionic acid (Dap).
  • Dab ⁇ , ⁇ -diaminobutyric acid
  • Dap ⁇ , ⁇ -diaminobutyric acid
  • -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is ⁇ -diaminobutyric acid (Dab), a serine residue, a lysine residue, or ⁇ . ⁇ -diaminopropionic acid (Dap).
  • Dab ⁇ -diaminobutyric acid
  • Dap ⁇ . ⁇ -diaminopropionic acid
  • -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is ⁇ . ⁇ -diaminobutyric acid (Dab) or a. ⁇ -diaminopropionic acid (Dap), such as L-Dab or L-Dap.
  • -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is ⁇ , ⁇ -diaminobutyric acid (Dab) or a, ⁇ -diaminopropionic acid (Dap), such as L-Dab or L-Dap.
  • -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a lysine residue, such as L-Lys.
  • -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is Dab, such as L-Dab.
  • Compounds of the invention where -R 4 is a Dab side chain are obtainable from compounds such as Polymyxin B.
  • Compounds where -R 4 is a Dap side chain may be prepared using the methods described in WO 2012/168820.
  • Compounds where -R 4 is a serine side chain may be prepared using the methods described by Vaara et al. (see, for example, Antimicrob. Agents Chemother. 2008, 52, 3229).
  • the amino acid residue including the group -R 8 corresponds to position 2 in the polymyxins.
  • -R 8 is methyl.
  • the resulting amino acid is therefore Thr.
  • -R 8 is H.
  • the resulting amino acid is therefore Ser.
  • the group -X- may be selected from -NHC(O)-, -C(O)-, -OC(O)-, -CH 2 - and -SO2-.
  • -X- is selected from -C(O)-, -SO2- and -CH 2 -.
  • -X- is -C(O)-.
  • -X- is -SO2-.
  • -X- is -CH2-.
  • the right-hand side of the group -X- is the point of attachment to NH, the amino terminal of the amino acid at position 2.
  • the left-hand side of the group -X- is the point of attachment to -R 5 or -R 15 .
  • C x . y in terms such as "C4-7 heterocyclyl", and the like, refers to the number of ring atoms, which may be carbon atoms or heteroatoms (e.g., N, O, S).
  • piperidinyl is an example of a Ceheterocycyl group.
  • heterocyclyl in reference to the group -D refers to a group (1 ) which has one or more heteroatoms (e.g., N, O, S) forming part of a ring system, wherein the ring system comprises one ring or two or more fused rings, wherein at least one ring of the ring system is a non-aromatic ring, and (2) which is attached to the rest of the molecule by a non-aromatic ring atom (i.e., a ring atom that is part of a non-aromatic ring that is part of the ring system).
  • a non-aromatic ring atom i.e., a ring atom that is part of a non-aromatic ring that is part of the ring system.
  • piperidino and piperidin-4-yl are both examples of a Ceheterocycyl group
  • 2,3-dihydro-1 H-indol-1-yl is an example of a Cgheterocycyl group
  • both decahydro- quinolin-5-yl and 1.2,3.4-tetrahydro uinolin-4-yl are examples of a Cioheterocyclyl group.
  • each ring is non-aromatic.
  • the heterocyclyl group comprises one ring.
  • cycloalkyl refers to a group (1 ) which has a ring system comprising one ring or two or more fused rings, wherein one ring of the fused ring system may be an aromatic ring, and (2) which is attached to the rest of the molecule by a non-aromatic ring atom (i.e., a ring atom that is part of a non-aromatic ring that is part of the ring system).
  • cycloalkyl is an example of a Ce cycloalkyl group
  • tetralin-2-yl is an example of a Cio cycloalkyl group.
  • each ring is non-aromatic.
  • the cycloalkyl group comprises one ring.
  • heteroaryl refers to a group (1 ) which has one or more heteroatoms (e.g., N, O, S) forming part of a ring system, wherein the ring system comprises one ring or two or more fused rings, wherein at least one ring of the ring system is an aromatic ring, and (2) which is attached to the rest of the molecule by an aromatic ring atom (i.e., a ring atom that is part of an aromatic ring that is part of the ring system).
  • heteroatoms e.g., N, O, S
  • pyridyl is an example of a Ccheteroaryl group
  • isoquinolyl is an example of a Cioheteroaryl group
  • 1 ,2.3,4-tetrahydro-isoquinoline-7-yl is an example of a Cioheteroaryl group.
  • each ring is an aromatic ring.
  • the heteroaryl group comprises one aromatic ring.
  • a heteroaryl group may also include a pyridonyl group, which may be regarded as a structure corresponding to a pyridinyl group having a 2- or 4- hydroxyl substituent.
  • a heteroaryl group is not a pyridonyl group.
  • Carboaryl refers to a group (1 ) which has a ring system comprising one ring or two or more fused rings, wherein at least one ring of the ring system is an aromatic ring, and (2) which is attached to the rest of the molecule by an aromatic ring atom (i.e., a ring atom that is part of an aromatic ring that is part of the ring system).
  • aromatic ring atom i.e., a ring atom that is part of an aromatic ring that is part of the ring system.
  • phenyl is an example of a Ce carboaryl group
  • tetralin-6-yl is an example of a Cio carboaryl group.
  • each ring is an aromatic ring.
  • ring may be a carbocycle (such as shown above for tetralin), or the ring may be a heterocycle, as shown below for the group
  • salts of compound of formula (III) include all pharmaceutically acceptable salts, such as, without limitation, acid addition salts of strong mineral acids such as HCI and HBr salts and addition salts of strong organic acids such as a methanesulfonic acid salt. Further examples of salts include sulphates and acetates such as trifluoroacetate or trichloroacetate.
  • the salt is an acetate salt.
  • the compounds of the present disclosure are provided as a sulphate salt or a trifluoroacetic acid (TFA) salt. In one embodiment the compounds of the present disclosure are provided as acetate salts.
  • a compound of formula (III) can also be formulated as prodrug.
  • Prodrugs can include an antibacterial compound herein described in which one or more amino groups are protected with a group which can be cleaved in vivo, to liberate the biologically active compound.
  • the prodrug is an ' amine prodrug". Examples of amine prodrugs include sulphomethyl, as described in e.g., Bergen et al, Antimicrob.
  • a compound of formula (III) is provided as a prodrug.
  • a reference to a compound of formula (III) is also a reference to a solvate of that compound.
  • solvates include hydrates.
  • a compound of formula (III) includes a compound where an atom is replaced by a naturally occurring or non-naturally occurring isotope.
  • the isotope is a stable isotope.
  • a compound described here includes, for example deuterium containing compounds and the like.
  • H may be in any isotopic form, including 1 H, 2 H (D), and 3 H (T);
  • C may be in any isotopic form, including 12 C, 13 C, and 14 C;
  • O may be in any isotopic form, including 16 0 and 18 0; and the like.
  • Certain compounds of formula (III) may exist in one or more particular geometric, optical, enantiomeric, diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r- forms; endo- and exo-forms; R-, S-, and meso-forms; D- and L-forms; d- and l-forms; (+) and (-) forms; keto-, enol-, and enolate-forms; syn- and anti-forms; synclinal- and anticlinal-forms; a- and ⁇ -forms; axial and equatorial forms; boat-, chair-, twist-, envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as
  • isomers (or “isomeric forms”). Note that, except as discussed below for tautomeric forms, specifically excluded from the term “isomers,” as used herein, are structural (or constitutional) isomers (i.e., isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, -OCH3, is not to be construed as a reference to its structural isomer, a hydroxymethyl group, -CH2OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its structural isomer, meta- chlorophenyl.
  • Ci-ealkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and para- methoxyphenyl).
  • a reference to a particular compound includes all such isomeric forms, including mixtures (e.g., racemic mixtures) thereof.
  • Methods for the preparation e.g., asymmetric synthesis
  • separation e.g., fractional crystallisation and
  • One aspect of the present invention pertains to compounds in substantially purified form and/or in a form substantially free from contaminants.
  • the substantially purified form is at least 50% by weight, e.g., at least 60% by weight, e.g., at least 70% by weight, e.g., at least 80% by weight, e.g., at least 90% by weight, e.g., at least 95% by weight, e.g., at least 97% by weight, e.g., at least 98% by weight, e.g., at least 99% by weight.
  • substantially purified form refers to the compound in any
  • the substantially purified form refers to a mixture of stereoisomers, i.e., purified with respect to other compounds.
  • the substantially purified form refers to one stereoisomer, e.g., optically pure stereoisomer.
  • the substantially purified form refers to a mixture of enantiomers.
  • the substantially purified form refers to an equimolar mixture of enantiomers (i.e., a racemic mixture, a racemate).
  • the substantially purified form refers to one enantiomer, e.g., optically pure enantiomer.
  • the contaminants represent no more than 50% by weight, e.g., no more than 40% by weight, e.g., no more than 30% by weight, e.g., no more than 20% by weight, e.g., no more than 10% by weight, e.g., no more than 5% by weight, e.g., no more than 3% by weight, e.g., no more than 2% by weight, e.g., no more than 1 % by weight.
  • the contaminants refer to other compounds, that is, other than
  • the contaminants refer to other compounds and other stereoisomers. In one embodiment, the contaminants refer to other compounds and the other enantiomer.
  • the substantially purified form is at least 60% optically pure (i.e., 60% of the compound, on a molar basis, is the desired stereoisomer or enantiomer, and 40% is the undesired stereoisomer or enantiomer), e.g., at least 70% optically pure, e.g., at least 80% optically pure, e.g., at least 90% optically pure, e.g., at least 95% optically pure, e.g., at least 97% optically pure, e.g., at least 98% optically pure, e.g., at least 99% optically pure.
  • the compounds of the invention also include the chemically protected forms thereof.
  • amino functionality within the compound may be protected as the ferf-butoxy (-Boc) form.
  • hydroxy I functionality within the compound may be protected as the iert-butyl (f-Bu) form.
  • Protected froms are discussed in detail in the section below. Protected Forms
  • functionality such as amino functionality
  • a protecting group is provided to mask the reactive functionality, and this protecting groups may be removed at a later stage of the synthesis to reveal the original reactive functionality.
  • a compound of formula (Ilia) is provided, and salts, solvates and hydrates thereof, which is a compound of formula (III) in protected form.
  • amino, hydroxyl, carboxyl and thiol functionality present in compound (III) may be protected with a protecting group, such as described herein.
  • the compound of formula (Ilia) may be an intermediate for the preparation of the compound of formula (III).
  • compound (III) may be prepared from compound (Ilia), for example by removal of the protecting groups ("deprotection").
  • the protected form is a compound where amino, hydroxyl, thiol, and/or carboxyl functionality is protected (masked) by a protecting group.
  • the protected form is a compound where the side chain functionality of the amino acids residues with the compound are protected.
  • the amino acid residues at positions 5, 8 and 9 are Dab residues, and the side chain of the Dab residue includes amino functionality.
  • the amino acid functionality of each Dab residue may be protected with an amino protecting group, as described herein.
  • -R 3 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is an amino acid residue where the side chain includes hydroxyl functionality.
  • An example of an amino acid residue including -R 3 is threonine.
  • the hydroxyl functionality of this residue may be protected with a hydroxy I protecting group, as described herein.
  • the group -R 8 is part of an amino acid residue where the side chain includes hydroxyl functionality.
  • the amino acid residue including group -R 8 may be serine or threonine.
  • the hydroxyl functionality of these residues may be protected with a hydroxyl protecting group, as described herein.
  • the group -R 4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is an amino acid residue where the side chain includes hydroxyl functionality or amino functionality.
  • An example of an amino acid residue including -R 4 is Dab.
  • the hydroxyl or amino functionality of these residues may be protected with a hydroxyl or amino protecting group, as described herein.
  • the group -R 15 contains functionality such as amino, hydroxyl carboxyl or thiol functionality.
  • the amino, hydroxyl carboxyl or thiol functionality may be protected with amino, hydroxyl carboxyl or thiol protecting groups, as described herein.
  • a protected polymyxin compound may be prepared from appropriately protected amino acid starting materials.
  • Velkov et al. describe the step-wise preparation of polymyxin compounds on the solid-phase using suitably protected amino acids. The use of protected-forms of threonine and Dab is disclosed (see Supplementary Information). Velkov et al. do not describe compounds of formula (III), for at least the reason that the group -R 15 is not described or exemplified in Velkov et al.
  • a protecting group is it is removable under conditions that do not substantially disrupt the structure of the polymyxin core, for example conditions that do not alter the stereochemistry of the amino acid residues.
  • the protecting groups are acid-labile, base labile, or are removable under reducing conditions.
  • Example protecting groups for amino functionality include Boc (tert-butoxycabonyl), Bn
  • Example protecting groups for aromatic nitrogen functionality includes Boc, Mtt, Trt and Dnp (dinitrophenyl).
  • the protecting group for amino functionality is selected from Boc, CbZ, Bn and Fmoc and HSCVFmoc.
  • the protecting group for amino functionality is Boc, Fmoc or CbZ.
  • Example protecting groups for hydroxy I functionality include Trt (trityl), Bn (benzyl), tBu (terf-butyl), and 2-acetamido-2-deoxy-3.4,6-tri-Oacetyl-a-galactopyranosyl.
  • the protecting group for hydroxyl functionality is Trt.
  • protecting groups for hydroxyl functionality include silyl ether protecting groups, such as TMS, TES, TBS, TIPS, TBDMS, and TBDPS. Such protecting groups are removable with TBAF, for example.
  • Example protecting groups for carboxyl functionality include Bn (benzyl, Bz), tBu (tert-butyl), TMSET (trimethylsilylethyl) and Dmab ( ⁇ 1-[4,4-dimethyl-2.6-dioxocylcohex-1 -ylidene]-3- methylbutyljamino benzyl).
  • only some types of functionality are protected.
  • only amino groups may be protected, such as amino groups in the side chain of an amino acid residue.
  • amino groups and hydroxyl groups are protected.
  • the compounds of formula (III) may each be used together with a second agent.
  • the inventors have found that such combinations have greater biological activity than would be expected from the individual activity of both compounds.
  • the compounds of formula (III) can be used to potentiate the activity of the second agent.
  • the compounds of formula (III) may be used together with a second agent to enhance the antimicrobial activity of that agent, for example against Gram-negative bacteria.
  • the compounds of formula (III) act on the outer membrane of a cell e.g. a Gram-negative bacterial cell, to facilitate the uptake of the second agent into that cell.
  • agents that are otherwise incapable or poor at crossing the outer membrane may be taken up into a target cell by the action of the compounds of formula (III).
  • the combination of a compound of formula (III) with the second agent is active against Gram-negative bacteria.
  • the second agent is an agent having a measured MIC value against a particular microorganism, such as a bacterium, that is less than 10, less than 5, or less than 1 micrograms/mL.
  • the microorganism may be a Gram-negative bacteria, such as a Gram- negative bacteria selected from the group consisting of E. coli, S. enterica, K. pneumoniae, K. oxytoca; E. cloacae. E. aerogenes, E. agglomerans, A. caicoaceticus, A. baumannii; Pseudomonas aeruginosa, Stenotrophomonas maltophila, Providencia stuartii, P. mirabilis, and P. vulgaris.
  • Examples of second agents that have activity against Gram-negative bacteria include beta-lactams, tetracyclines, aminoglycosides and quinolones.
  • the second agent is an agent having a measured MIC value against a particular microorganism, such as a Gram-negative bacterium, that is more than 4, more than 8, more than 16 or more than 32 micrograms/mL.
  • the second agent may be active against Gram-positive bacteria.
  • the second agent is an agent having a measured MIC value against a particular Gram-positive bacterium that is less than 10, less than 5, or less than 1 micrograms/mL.
  • the compound of formula (III) acts to facilitate the uptake of the second agent into the Gram-negative bacterial cell. The second agent is therefore able to act on a target within the Gram-negative bacterial cell, which target may be the same as the second agent's target in a Gram-positive bacterial cell.
  • the Gram-positive bacteria may be selected from the group consisting of Staphylococcus and Streptococcus bacteria, such as S. aureus (including MRSA), S. epidermis, E. faecalis, and E. faecium.
  • Examples of second agents that have activity against Gram-positive bacteria (at the MIC values given above, for example), and moderate activity against Gram-negative bacteria include rifampicin, novobiocin, macrolides, pleuromutilins.
  • a compound having moderate activity against Gram-negative bacteria may have a measured MIC value against a Gram-negative bacterium that is less than 32, less than 64, or less than 128 micrograms/mL.
  • agents having activity against Gram-positive bacteria and which are essentially inactive against Gram-negative bacteria include fusidic acid, oxazolidinines (e.g. linezolid), glycopeptides (e.g. vancomycin), daptomycin and lantibiotics.
  • a compound having essentially no activity against Gram-negative bacteria may have a measured MIC value against a Gram-negative bacterium that is more than 32, more then 64, more than 128, more than 256 micrograms/mL.
  • a measured MIC value against a Gram-negative bacterium that is more than 32, more then 64, more than 128, more than 256 micrograms/mL.
  • such agents are not necessarily suitable for use against Gram- negative bacteria owing to their relatively poor ability to cross the outer membrane of a Gram-negative bacterial cell.
  • such agents are suitable for use.
  • the active agent may be selected from the group consisting of rifampicin (rifampin), rifabutin, rifalazil, rifapentine, rifaximin, aztreonam, oxacillin, novobiocin, fusidic acid, azithromycin, ciprofloxacin, meropenem, tigecycline, erythromycin, clarithromycin and mupirocin, and pharmaceutically acceptable salts, solvates and prodrug forms thereof.
  • rifampicin rifampin
  • rifabutin rifalazil
  • rifapentine rifaximin
  • aztreonam oxacillin
  • fusidic acid azithromycin
  • ciprofloxacin ciprofloxacin
  • meropenem meropenem
  • tigecycline erythromycin
  • clarithromycin and mupirocin tigecycl
  • the rifamycin family includes isolates rifamycin A, B, C, D, E, S and SV, and synthetically derivatised versions of these compounds, such as rifampicin (rifampin), rifabutin, rifalazil, rifapentine, and rifaximin, and pharmaceutically acceptable salts and solvates thereof.
  • the active agent is rifampicin (rifampin) and pharmaceutically acceptable salts, solvates and prodrug forms thereof.
  • a second active agent for example a second active agent that is an antimicrobial agent.
  • the compounds of formula (III) are for use in a method of treatment of the human or animal body by therapy.
  • a compound of formula (III) may be administered to a mammalian subject, such as a human, in order to treat a microbial infection.
  • Another aspect of the present invention pertains to use of a compound of formula (III) in the manufacture of a medicament for use in treatment.
  • the medicament comprises a compound of formula (III).
  • the medicament is for use in the treatment of a microbial infection.
  • microbial infection refers to the invasion of the host animal by pathogenic microbes. This includes the excessive growth of microbes that are normally present in or on the body of an animal. More generally, a microbial infection can be any situation in which the presence of a microbial population(s) is damaging to a host animal. Thus, an animal is "suffering" from a microbial infection when excessive numbers of a microbial population are present in or on an animal's body, or when the presence of a microbial population(s) is damaging the cells or other tissue of an animal.
  • the compounds may be used to treat a subject having a microbial infection, or at risk of infection from a microorganism, such as a bacterium.
  • the microbial infection may be a bacterial infection such as a Gram-negative bacterial infection.
  • Gram-negative bacteria examples include, but are not limited to, Escherichia spp., Klebsiella spp., Enterobacter spp., Salmonella spp., Shigella spp., Citrobacter spp., Morganella morganii. Yersinia pseudotuberculosis and other Enterobacteriaceae,
  • Medically relevant Gram-negative cocci include three organisms, which cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis).
  • Medically relevant Gram-negative bacilli include a multitude of species. Some of them primarily cause respiratory problems (Hemophilus influenzae, Klebsiella pneumoniae,
  • Legionella pneumophila Pseudomonas aeruginosa
  • urinary problems Escherichia coli, Enterobacter cloacae
  • Helicobacter pylori. Salmonella enterica Gram-negative bacteria associated with nosocomial infections include Acinetobacter baumannii, which causes bacteremia, secondary meningitis, and ventilator-associated pneumonia in intensive-care units of hospital establishments.
  • the Gram-negative bacterial species is selected from the group consisting of £. coli, S. enterica, K. pneumoniae, K. oxytoca; E. cloacae, E. aerogenes, E. agglomerans, A. calcoaceticus, A. baumannii; Pseudomonas aeruginosa,
  • Stenotrophomonas maltophila Providencia stuartii, P. mirabilis, and P. vulgaris.
  • the Gram-negative bacterial species is selected from the group consisting of E. coli, K. pneumoniae, Pseudomonas aeruginosa, and A. baumannii.
  • the compounds of formula (III) or compositions comprising the same are useful for the treatment of skin and soft tissue infections, gastrointestinal infection, urinary tract infection, pneumonia, sepsis, intra-abdominal infection and obstetrical/gynaecological infections.
  • the infections may be Gram-positive or Gram-negative bacterial infections.
  • the compounds of formula (III) or compositions comprising the same are useful for the treatment of Pseudomonas infections including P. aeruginosa infection, for example skin and soft tissue infections, gastrointestinal infection, urinary tract infection, pneumonia and sepsis.
  • the compounds of formula (III) or compositions comprising the same are useful for the treatment of Acinetobacter infections including A. baumanii infection, for pneumonia, urinary tract infection and sepsis.
  • the compounds of formula (III) or compositions comprising the same are useful for the treatment of Klebsiella infections including K. pneumoniae infection, for pneumonia, urinary tract infection, meningitis and sepsis.
  • the compounds of formula (III) or compositions comprising the same are useful for the treatment of E. coli infection including E. coli infections, for bacteremia, cholecystitis, cholangitis, urinary tract infection, neonatal meningitis and pneumonia.
  • E. coli infection including E. coli infections, for bacteremia, cholecystitis, cholangitis, urinary tract infection, neonatal meningitis and pneumonia.
  • treatment refers generally to treatment and therapy, whether of a human or an animal (e.g., in veterinary applications), in which some desired therapeutic effect is achieved, for example, the inhibition of the progress of the condition, and includes a reduction in the rate of progress, a halt in the rate of progress, alleviation of symptoms of the condition, amelioration of the condition, and cure of the condition.
  • Treatment as a prophylactic measure i.e., prophylaxis
  • treatment is also included. For example, use with patients who have not yet developed the condition, but who are at risk of developing the condition, is encompassed by the term "treatment.”
  • terapéuticaally-effective amount refers to that amount of a compound, or a material, composition or dosage form comprising a compound, which is effective for producing some desired therapeutic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.
  • treatment includes combination treatments and therapies, as described herein, in which two or more treatments or therapies are combined, for example, sequentially or simultaneously.
  • a compound of formula (III) may be administered in conjunction with an active agent.
  • Administration may be simultaneous, separate or sequential.
  • a compound of formula (III) and a second agent are administered to a subject by two different routes of administration which occur at the same time. This may occur for example where one agent is administered by infusion and the other is given orally during the course of the infusion.
  • quential it is meant that the two agents are administered at different points in time, provided that the activity of the first administered agent is present and ongoing in the subject at the time the second agent is administered.
  • the active agent may be administered first, followed by the compound of formula (III).
  • the order and timing of the administration of the compound and second agent in the combination treatment will depend upon the pharmacokinetic properties of each.
  • the amount of the compound of formula (III) to be administered to a subject will ultimately depend upon the nature of the subject and the disease to be treated. Likewise, the amount of the active agent to be administered to a subject will ultimately depend upon the nature of the subject and the disease to be treated.
  • the present invention provides a pharmaceutical composition
  • a pharmaceutical composition comprising a compound of formula (III) together with a pharmaceutically acceptable carrier.
  • the pharmaceutical composition may additionally comprise a second active agent.
  • the second agent may be separately formulated from the compound of formula optionally (III). The comments below made in relation to the compound of formula optionally (III) may therefore also apply to the second agent, as separately formulated.
  • the compound of formula (III) While it is possible for the compound of formula (III) to be administered alone or together with the second agent, it is preferable to present it as a pharmaceutical formulation (e.g., composition, preparation, medicament) comprising at least one compound of formula (III), as described herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, including, but not limited to, pharmaceutically acceptable carriers, diluents, excipients, adjuvants, fillers, buffers, preservatives, antioxidants, lubricants, stabilisers, solubilisers, surfactants (e.g., wetting agents), masking agents, colouring agents, flavouring agents, and sweetening agents.
  • the formulation may further comprise other active agents, for example, other therapeutic or prophylactic agents.
  • the present invention further provides pharmaceutical compositions, as defined above, and methods of making a pharmaceutical composition comprising admixing at least one compound of formula (III), as described herein, together with one or more other
  • composition optionally further comprises the second active agent in a predetermined amount.
  • pharmaceutically acceptable as used herein, pertains to compounds,
  • ingredients, materials, compositions, dosage forms, etc. which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of the subject in question (e.g., human) without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio.
  • Each carrier, diluent, excipient, etc. must also be "acceptable" in the sense of being compatible with the other ingredients of the formulation.
  • Suitable carriers, diluents, excipients, etc. can be found in standard pharmaceutical texts, for example, Remington's Pharmaceutical Sciences, 18th edition, Mack Publishing Company, Easton, Pa., 1990; and Handbook of Pharmaceutical Excipients, 5th edition, 2005.
  • the formulations may be prepared by any methods well known in the art of pharmacy. Such methods include the step of bringing into association the compound of formula (III) with a carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the compound with carriers (e.g., liquid carriers, finely divided solid carrier, etc.), and then shaping the product, if necessary.
  • carriers e.g., liquid carriers, finely divided solid carrier, etc.
  • the formulation may be prepared to provide for rapid or slow release; immediate, delayed, timed, or sustained release; or a combination thereof.
  • Formulations may suitably be in the form of liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions (e.g., oil-in-water, water-in-oil), elixirs, syrups, electuaries, mouthwashes, drops, tablets (including, e.g., coated tablets), granules, powders, losenges, pastilles, capsules (including, e.g., hard and soft gelatin capsules), cachets, pills, ampoules, boluses, suppositories, pessaries, tinctures, gels, pastes, ointments, creams, lotions, oils, foams, sprays, mists, or aerosols.
  • Formulations may suitably be provided as a patch, adhesive plaster, bandage, dressing, or the like which is impregnated with one or more compounds and optionally one or more other pharmaceutically acceptable ingredients, including, for example, penetration, permeation, and absorption enhancers. Formulations may also suitably be provided in the form of a depot or reservoir.
  • the compound may be dissolved in, suspended in, or admixed with one or more other pharmaceutically acceptable ingredients.
  • the compound may be presented in a liposome or other microparticulate which is designed to target the compound, for example, to blood components or one or more organs. Where a liposome is used, it is noted that the liposome may contain both the compound of formula (III) and the second agent.
  • Formulations suitable for oral administration include liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions (e.g., oil-in-water, water-in-oil), elixirs, syrups, electuaries, tablets, granules, powders, capsules, cachets, pills, ampoules, boluses.
  • Formulations suitable for buccal administration include mouthwashes, losenges, pastilles, as well as patches, adhesive plasters, depots, and reservoirs.
  • Losenges typically comprise the compound in a flavoured basis, usually sucrose and acacia or tragacanth.
  • Pastilles typically comprise the compound in an inert matrix, such as gelatin and glycerin, or sucrose and acacia.
  • Mouthwashes typically comprise the compound in a suitable liquid carrier.
  • Formulations suitable for sublingual administration include tablets, losenges, pastilles, capsules, and pills.
  • Formulations suitable for oral transmucosal administration include liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions (e.g., oil-in- water, water-in-oil), mouthwashes, losenges, pastilles, as well as patches, adhesive plasters, depots, and reservoirs.
  • solutions e.g., aqueous, non-aqueous
  • suspensions e.g., aqueous, non-aqueous
  • emulsions e.g., oil-in- water, water-in-oil
  • mouthwashes e.g., losenges, pastilles, as well as patches, adhesive plasters, depots, and reservoirs.
  • Formulations suitable for non-oral transmucosal administration include liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions
  • Formulations suitable for transdermal administration include gels, pastes, ointments, creams, lotions, and oils, as well as patches, adhesive plasters, bandages, dressings, depots, and reservoirs.
  • Tablets may be made by conventional means, e.g., compression or moulding, optionally with one or more accessory ingredients.
  • Compressed tablets may be prepared by compressing in a suitable machine the compound in a free-flowing form such as a powder or granules, optionally mixed with one or more binders (e.g., povidone, gelatin, acacia, sorbitol, tragacanth, hydroxypropylmethyl cellulose); fillers or diluents (e.g., lactose, microcrystalline cellulose, calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc, silica); disintegrants (e.g., sodium starch glycolate, cross-linked povidone, cross-linked sodium carboxymethyl cellulose); surface-active or dispersing or wetting agents (e.g., sodium lauryl sulfate); preservatives (e.g., methyl p-hydroxybenzoate, propyl
  • Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent.
  • the tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the compound therein using, for example, hydroxypropylmethyl cellulose in varying proportions to provide the desired release profile.
  • Tablets may optionally be provided with a coating, for example, to affect release, for example an enteric coating, to provide release in parts of the gut other than the stomach.
  • Ointments are typically prepared from the compound and a paraffinic or a water-miscible ointment base.
  • Creams are typically prepared from the compound and an oil-in-water cream base.
  • the aqueous phase of the cream base may include, for example, at least about 30% w/w of a polyhydric alcohol, i.e., an alcohol having two or more hydroxy I groups such as propylene glycol, butane-1.3-diol, mannitol, sorbitol, glycerol and polyethylene glycol and mixtures thereof.
  • the topical formulations may desirably include a compound which enhances absorption or penetration of the compound through the skin or other affected areas. Examples of such dermal penetration enhancers include dimethylsulfoxide and related analogues.
  • Emulsions are typically prepared from the compound and an oily phase, which may optionally comprise merely an emulsifier (otherwise known as an emulgent), or it may comprises a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil.
  • an emulsifier also known as an emulgent
  • a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabiliser. It is also preferred to include both an oil and a fat.
  • emulsifier(s) with or without stabiliser(s) make up the so-called emulsifying wax, and the wax together with the oil and/or fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations.
  • Suitable emulgents and emulsion stabilisers include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate and sodium lauryl sulfate.
  • suitable oils or fats for the formulation is based on achieving the desired cosmetic properties, since the solubility of the compound in most oils likely to be used in pharmaceutical emulsion formulations may be very low.
  • the cream should preferably be a non-greasy, non-staining and washable product with suitable consistency to avoid leakage from tubes or other containers.
  • Straight or branched chain, mono- or dibasic a Iky I esters such as di-isoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a blend of branched chain esters known as Crodamol CAP may be used, the last three being preferred esters. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and/or liquid paraffin or other mineral oils can be used.
  • Formulations suitable for intranasal administration, where the carrier is a liquid include, for example, nasal spray, nasal drops, or by aerosol administration by nebuliser, include aqueous or oily solutions of the compound.
  • a dry powder delivery may be used as an alternative to nebulised aerosols.
  • Formulations suitable for intranasal administration, where the carrier is a solid include, for example, those presented as a coarse powder having a particle size, for example, in the range of about 20 to about 500 microns which is administered in the manner in which snuff is taken, i.e., by rapid inhalation through the nasal passage from a container of the powder held close up to the nose.
  • Formulations suitable for pulmonary administration include those presented as an aerosol spray from a pressurised pack, with the use of a suitable propellant, such as dichlorodifluoromethane, trichlorofluoromethane, dichoro- tetrafluoroethane, carbon dioxide, or other suitable gases.
  • a formulaton for pulmonary administration may be formulated for administration from a nebuliser or a dry powder inhaler.
  • the formulation may be provided with carriers or liposomes to provide a suitable particle size to reach the appropriate parts of the lung, to aid delivery of an appropriate does to enhance retention in the lung tissue.
  • Formulations suitable for ocular administration include eye drops wherein the compound is dissolved or suspended in a suitable carrier, especially an aqueous solvent for the compound.
  • Formulations suitable for rectal administration may be presented as a suppository with a suitable base comprising, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols, for example, cocoa butter or a salicylate; or as a solution or suspension for treatment by enema.
  • Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the compound, such carriers as are known in the art to be appropriate.
  • Formulations suitable for parenteral administration include aqueous or non-aqueous, isotonic, pyrogen-free, sterile liquids (e.g., solutions, suspensions), in which the compound is dissolved, suspended, or otherwise provided (e.g., in a liposome or other microparticulate).
  • Such liquids may additional contain other pharmaceutically acceptable ingredients, such as anti-oxidants, buffers, preservatives, stabilisers, bacteriostats, suspending agents, thickening agents, and solutes which render the formulation isotonic with the blood (or other relevant bodily fluid) of the intended recipient.
  • excipients include, for example, water, alcohols, polyols, glycerol, vegetable oils, and the like.
  • Suitable isotonic carriers for use in such formulations include Sodium Chloride Injection, Ringer's Solution, or Lactated Ringer's Injection.
  • concentration of the compound in the liquid is from about 1 ng/mL to about 100 pg/mL, for example from about 10 ng/mL to about 10 g/mL, for example from about 10 ng/mL to about 1 g/mL.
  • the formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets.
  • the methods of the invention may comprise administering to a subject an effective amount of a compound of formula (III) so as to provide an antimicrobial effect.
  • the compound of formula (III) may be administered at an amount sufficient to potentiate the activity of a second active agent.
  • the second active agent is administered to a subject at an effective amount so as to provide an antimicrobial effect.
  • appropriate dosages of the compound of formula (III) or the active agent, and compositions comprising the compound of formula (III) or the active agent can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of therapeutic benefit against any risk or deleterious side effects.
  • the selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound of formula (III) or the active agent, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and/or materials used in combination, the severity of the condition, and the species, sex, age, weight, condition, general health, and prior medical history of the patient.
  • the amount of compound of formula (III) or the active agent and route of administration will ultimately be at the discretion of the physician, veterinarian, or clinician, although generally the dosage will be selected to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects.
  • Administration can be effected in one dose, continuously or intermittently (e.g., in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of the therapy, the target cell(s) being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician, veterinarian, or clinician.
  • a suitable dose of a compound of formula (III) or the active agent is in the range of about 10 pg to about 250 mg (more typically about 100 g to about 25 mg) per kilogram body weight of the subject per day. Where the compound of formula (III) or the active agent is a salt, an ester, an amide, a prodrug, or the like, the amount administered is calculated on the basis of the parent compound and so the actual weight to be used is increased proportionately.
  • kits comprising (a) a compound of formula (III), or a composition comprising a compound as defined in any one of formula (III), e.g., preferably provided in a suitable container and/or with suitable packaging; and (b) instructions for use, e.g., written instructions on how to administer the compound or composition.
  • the written instructions may also include a list of indications for which the compound of formula (III) is a suitable treatment.
  • the kit further comprises (c) a second active agent, or a composition comprising the second active agent.
  • the written instructions may also include a list of indications for which the second active agent, together with the compound of formula (III), is suitable for treatment.
  • a compound of formula (III), a second agent, or a pharmaceutical composition comprising the compound of formula (III) may be administered to a subject by any convenient route of administration, whether systemically/peripherally or topically (i.e., at the site of desired action).
  • Routes of administration include, but are not limited to, oral (e.g., by ingestion); buccal;
  • transdermal including, e.g., by a patch, plaster, etc.
  • transmucosal including, e.g., by a patch, plaster, etc.
  • intranasal e.g., by nasal spray
  • ocular e.g., by eyedrops
  • pulmonary e.g., by inhalation or insufflation therapy using, e.g., via an aerosol, e.g., through the mouth or nose
  • rectal e.g., by suppository or enema
  • vaginal e.g., by pessary
  • parenteral for example, by injection, including subcutaneous, intradermal, intramuscular, intravenous, intraarterial, intracardiac, intrathecal, intraspinal, intracapsular, subcapsular, intraorbital, intraperitoneal, intratracheal, subcuticular, intraarticular, subarachnoid, and intrasternal; by implant of a depot or reservoir, for example, subcutaneously or
  • the subject/patient may be a chordate, a vertebrate, a mammal, a placental mammal, a marsupial (e.g., kangaroo, wombat), a rodent (e.g., a guinea pig, a hamster, a rat, a mouse), murine (e.g., a mouse), a lagomorph (e.g., a rabbit), avian (e.g., a bird), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., a horse), porcine (e.g., a pig), ovine (e.g., a sheep), bovine (e.g., a cow), a primate, simian (e.g., a monkey or ape), a monkey (e.g., marmoset, baboon), an ape (e.g
  • the subject/patient is a human.
  • a non-human mammal may be a rodent.
  • Rodents include rats, mice, guinea pigs, chinchillas and other similarly-sized small rodents used in laboratory research.
  • Compounds of formula (III) can be prepared by conventional peptide synthesis, using methods known to those skilled in the art. Suitable methods include solution-phase synthesis such as described by Yamada et al, J. Peptide Res. 64, 2004, 43-50, or by solid-phase synthesis such as described by de Visser et al, J. Peptide Res, 61 , 2003, 298- 306, and Vaara et al, Antimicrob. Agents and Chemotherapy, 52, 2008. 3229-3236. These methods include a suitable protection strategy, and methods for the cyclisation step. Alternatively, compounds may be prepared from readily available polymyxins, for example by removal of the N-terminal amino acid of the polymyxin (residue 1 ). Such a method is described herein for the preparation of compounds based on residues 2-10 of polymyxins B and E.
  • the N terminal group of a deacylated polymyxin compound such as deacylated polymyxin B and deacylated polymyxin B nonapeptide
  • the side chains of the polymyxin compound may be selectively protected without protecting the N terminal group.
  • the N terminal group may then be reacted to provide the appropriate N terminal substituent.
  • the side chain protection may subsequently be removed.
  • a protected Polymyxin can also be cleaved to the corresponding hepta peptide by cleavage of amino acids 1 -3. Methods for this cleavage are described in WO 2012/168820, and WO 1988/00950. As shown herein this can be derivatised by coupling to appropriately substituted dipeptides or tripeptides to provide novel polymyxin derivatives.
  • Nomenclature - Compounds are named based on the natural polymyxin core from which they are synthetically derived.
  • the crude material was separated into 87 mL fractions and purified using 10 g SCX cartridge (* 6), eluting first with methanol (100 mL) and then 20% ammonia (aq, sp.g.880) in methanol (100 mL).
  • the ammonia fractions were isolated and evaporated to give the product as beige solid, yield 4.95 g, 60% m/z 482, [M+2H] 2 ' .
  • Mobile Phase B 90% Acetonitrile in 10% Water, 0.15 %TFA or 0.1 % formic
  • Colistin Polymyxin E
  • Nonapeptide 2.5 g, 2.69 mmol
  • water 35 mL
  • Dioxane 35 mL
  • triethylamine 35ml
  • the progress of the reaction was followed by LC-MS and reached completion after 10 minutes, whereupon the mixture was quenched by addition of 20% methanolic ammonia (25 mL).
  • the liquid phase was decanted and the residual solid was re-dissolved in water and extracted sequentially with dichloromethane and iso-butanol. Based on LC-MS analysis, the decanted liquid and both dichloromethane and iso-butanol extracts were pooled together followed by concentration in vacuo to give yellow gum which was loaded onto flash chromatography (Si 6 OA- 35-70). The column was eluted with 0-20% methanol (containing 2% ammonia) in dichloromethane.
  • This material (1 g) was dissolved in 1 ,4-butanediol (1 12.5 mL) and the mixture was stirred at 40 C overnight.
  • potassium phosphate 75 mL, 0.12 5M pH 8.0
  • the reaction was diluted by adding 1 12.5 mL butanediol and 75 mL potassium phosphate (0.125 M pH 8.0), but the white emulsion persisted.
  • the temperature of the reaction was reduced to 37 C and then Savinase 16L (250 L) was added and the reaction was stirred at room temperature overnight.
  • the reaction mixture was diluted with water (50ml) and was then extracted with DCM (100 mL) The DCM layer was collected and evaporated in vacuo to afford a colourless oil.
  • the resulting oil was diluted in 50 % methanol (aq.) and was loaded onto four preconditioned 10 g Varian Bond Elut SCX cartridges and the flow through was collected. The cartridges were washed with two column volumes of 50 % methanol (aq.) and then PMBH-B0C3 was eluted from the column using two column volumes of 20% ammonia in methanol.
  • Step 1 (S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy-butyrylamino)-4-tert- butoxycarbonylamino-butyric acid methyl ester
  • (S)-2-Benzyloxycarbonylamino-3-tert-butoxy-butyric acid DHCA salt (3.65 g, 7.4 mmol)
  • (S)-2-Amino-4-tert-butoxycarbonylamino-butyric acid methyl ester HCI salt 2.0 g, 7.4 mmol
  • DCM 60 mL
  • DMF 120 mL
  • N,N-diisopropylethylamine 3.85 mL, 22.1 mmol
  • aqueous phase was re-extracted with fresh solvent mixture (100 mL) and the combined organic extracts were successively washed with water (150 mL) and sat. NaHCOa solution (150 mL), dried (Na2S0 4 ) and concentrated to a colourless oil (3.72g).
  • This oil was purified by silica gel chromatography on a 100g SepPak cartridge, eluting with a solvent gradient of EtOAc/i-hexane (0-70%).
  • Step 4 Title Compound
  • the product from step 3 (5.41 g, 3.48 mmol), ammonium formate (6.6 g, 104.4 mmol) and 10% Pd-C (2.0 g) were charged to a flask under N 2 .
  • MeOH (270 mL) was added and the mixture was stirred under N 2 for 4.5h.
  • LCMS showed MH + for product and loss of starting material.
  • the mixture was filtered under suction through a pad of celite and washed through with MeOH (50 mL). The filtrate and washings were evaporated to a colourless oil which was partitioned between a solvent mixture of EtOAc/MeOH (4:1 )(250 mL) and water
  • Colistin sulphate (5.0 g, 3.95 mmol) was dissolved in acetonitrile (50 mL) and water (25 mL) and stirred at room temperature for 10 minutes. Triethylamine (3.2 mL, 23.0 mmol) was added and the mixture stirred for a further 10 minutes. Di-tert-butyl dicarbonate (5.0 g, 23.0 mmol) was subsequently added in one portion and the mixture stirred for 16 hours. Savinase (15 mL) was then added, followed by 4 M sodium hydroxide solution (0.5 mL) and the reaction mixture stirred at room temperature for 5 days. The mixture was diluted with ethyl acetate and water.
  • Step 1 The corresponding carboxylic acid (5 equiv with respect to the polymyxin substrate) was dissolved in dichloromethane (2 mL/mmol). A/,A/-Diisopropylethyalmine (5.0 equiv.) and 2-(1 H-7-Azabenzotriazol-1 -yl)-1 , 1.3, 3-tetra methyl uronium hexafluorophosphate (HATU) (5.0 equiv ) were then added to the reaction mixture. After 30 min stirring at room temperature compound of intermediate 2 or intermediate 4 (1.0 equiv.) was added.
  • HATU 3-tetra methyl uronium hexafluorophosphate
  • Step 2 The product from Step 1 was dissolved in dichloromethane (20 mL/mmol).
  • Trifluoroacetic acid 60 equiv. was added and the mixture was stirred at room temperature for 16 h, after which time LC-MS confirmed completion of the reaction.
  • the reaction mixture was concentrated in vacuo to leave the trifluoroacetate salt as a colourless oil. To this was added water (10 mL/mmol) and the mixture was sonicated for 5 min. To the resulting suspension was added 1 M NaHC0 3 until the mixture reached pH 9. The mixture was then passed through a 10 g C18 SPE column, eluting sequentially with 0, 40, 50, 60, 70, 80 and 100 % aqueous methanol. Product-containing fractions were pooled and evaporated.
  • Mobile Phase B 90% Acetonitrile in 10% Water, 0.15 %TFA or 0.1 % Formic acid
  • Injection volume 20 ⁇ .
  • Step 1 The BOC protected nonapeptide was prepared using the conditions of Method 1. After completion if the reaction, the crude reaction mixture was adsorbed onto silica and chromatographed on a silica cartridge, eluting with 0-20% methanol in dichloromethane. Product-containing fractions were combined and evaporated to a white foam. The product thus obtained was re-purified by silica gel chromatography to obtain the product as a white foam.
  • Step 2 The purified product from Step 2 was dissolved in dichloromethane (2 ml_), treated with TFA (1 mL) and the mixture stirred at room temperature for 1 hour. The solvent was evaporated and the residue azeotroped with toluene, to leave a white solid. This was dissolved in water (10 mL) and washed with dichloromethane (5 mL). The aqueous phase was evaporated to low volume and lyophilised overnight to afford the TFA salt of the product as a white solid.
  • Step 1 The protected polymyxin substrate (0.07 mmol) was dissolved in dichloromethane (4 mL), and treated with the corresponding carboxylic acid (1 .5 equiv with respect to the polymyxin substrate), A/,A/-Diisopropylethyalmine (3.0 equiv.), followed by HATU
  • Step 2 The Boc-protected derivative from Step 1 was dissolved in dichloromethane (3 mL) and treated with TFA (1 mL). The reaction mixture was stirred at room temperature until LCMS confirmed complete deprotection. The solvent was evaporated and the residue chromatogaphed by prep HPLC using the conditions of Method 3, step 6. Product- containing fractions were combined, evaporated to low volume, and lyophilised to afford the product as the TFA salt.
  • Step 1 Coupling of carboxylic acids to methyl esters of amino acid 1
  • Step 2 Hydrolysis of the methyl ester product from step 1
  • methanol 5 mL/mmol with respect to the methyl ester
  • step 4 Hydrolysis of the methyl ester product from step 3
  • step 3 was carried out in the same manner as that described in step 2, using the methyl ester from step 3.
  • the carboxylic acid product (m/z [M+H] + detectable in the LCMS spectrum) was isolated as a mixture of diastereoisomers.
  • Step 5 Coupling of the carboxylic acid product from step 4 with Tri-(Boc) Polymyxin B hepta peptide (intermediate 5)
  • Step 6 Deprotection of the Polymyxin B heptapeptide product from step 5
  • TFA (30 mL/mmol with respect to polypeptide) was added to a stirred solution of the polypeptide from step 5 in DCM (60 mL/mmol). The solution was stirred for 3.5 h then evaporated and dried under vacuum for 1 h. The residue was purified by HPLC (conditions below) and lyophilised to afford the TFA salt of the product as a white solid. Where a racemic acid was used in step 1 , the product is obtained as a mixture of diastereoisomers. (See Table 4 for examples).
  • Method 3B consists of steps 1-2 of Method 3A followed by coupling to BOC-protected PMBN (Intermediate 2) to give the protected deca peptide.
  • Deprotection following Method 3A, Step 5A for CBZ deprotection and Step 6 for Boc deprotection affords the desired compound.
  • a TFA salt (50 mg) was dissolved in water, and taken to pH 9 with 1 M NaHCOa. The mixture was then passed through a 1 g C18 SPE column, eluting with water (20 mL) followed by 80% methanol/water. Product-containing fractions were pooled treated with 0.1 M acetic acid (10 equiv.). The solution was concentrated under reduced pressure, then lyophilised overnight to afford the acetate salt as a white solid. Compound purity was assessed by HPLC using the conditions outlined in Table 2. Alternative Preparation of Acetate Salts
  • the products were purified by silica gel chromatography eluting with 0-30% diethyl ether in iso-hexane.
  • the first product to elute was assigned cis stereochemistry (470 mg, 40%) ⁇ when compared to the cyclohexyl analogue in Syn Comm, 2008, 38, 2799 ⁇ .
  • m/z 314 (M-tBu) + was assigned cis stereochemistry (470 mg, 40%) ⁇ when compared to the cyclohexyl analogue in Syn Comm, 2008, 38, 2799 ⁇ .
  • m/z 314 (M-tBu) + Further elution of the column gave the trans derivative (333mg, 28%).
  • Nickel chloride hexahydrate (609 mg, 2.6 mmol) was added to a stirred solution of
  • the pH of the aqueous layer was adjusted to pH 10 by the addition of 880 ammonia. After separation of the layers, the aqueous phase was re-extracted with ethyl acetate and then the combined organic layers were passed through a hydrophobic frit. The solvent was evaporated at reduced pressure and the residue purified by silica gel chromatography eluting with 0 - 30% ethyl acetate in iso-hexane to yield the title compound ⁇ relative stereochemistry, presumed cis ⁇ (133mg, 36%). m/z 370 (MH+), C21 H39N04 exact mass 369.288.
  • 5-isobutyl-nicotinic acid isobutyl ester 1 H NMR (CDCb) 9.10 (1 H, s), 8.60 (1 H, s), 8.10 (1 H, s), 4.15 (2H, d), 2.55 (2H, d), 2.10 (1 H, sept), 1.95 (1 H, sept), 1.05 (6H, d), 0.95 (6H, d).
  • 5-isobutyl-nictinic acid ethyl ester H NMR (CDCb) 9.05 (1 H, s), 8.55 (1 H, s), 8.10 (1 H, s), 4.45 (2H, q), 2.55 (2H, d), 1.90 (1 H, sept), 1 .45 (3H, t), 0.95 (6H, d).
  • Table 4A includes examples of the invention. All compounds were isolated as TFA salts unless otherwise specified. Compounds D9, D1 1 , D15 and D25 were also prepared as acetate salts according to the general method described herein.
  • the structures in the table depict the N-terminal group (-R) and side chain on the Polymyxin B hepta peptide scaffold (PMBH, below). Relative stereochemistry is depicted by heavy or dashed lines. Absolute stereochemistry is depicted by heavy or hashed wedged bonds.
  • the comparator compounds were Polymyxin B (PMB), C1 (NAB-739), and C2 (CB-182,804).
  • CB-182,804 (C2) is a polymyxin decapeptide derivative with an aryl urea substituent at the N-terminus, which has been claimed to have lower toxicity than Polymyxin B (shown as compound 5 in WO 2010/075416), and was prepared by the present inventors.
  • C1 was also prepared in- house, and corresponds to NAB-739 (as described by Vaara in, for example, WO 2008/01773.
  • Other comparator compounds were prepared in-house as shown in Table 4B.
  • Table 4C includes additional compounds of the invention. All compounds were prepared using general method 2A, as described above, apart from example D93 which used dicyclohexyl carbodiimide in the final coupling step. All compounds were isolated as TFA salts. Compounds D65, D67, D69, D76, D77, D78, D81 and D86 were also prepared as acetate salts.
  • Structures depict the N-terminal group and side chain on the Polymyxin B or Polymyxin E hepta peptide scaffold (PMBH or PMEH, below). Relative stereochemistry is depicted by heavy or dashed lines. Absolute stereochemistry is depicted by heavy or hashed wedged bonds.
  • Scaffold refers to polymyxin B (“B”) and polymyxin E (“E”) scaffolds, as shown below.
  • R- is the N-terminal and side-chain on the heptapeptide.
  • Scaffold refers to polymyxin B ("B”) and polymyxin E (“E”) scaffolds, as shown below.
  • R- is the N-terminal and side-chain on the heptapeptide.
  • PMBH Polymyxin B heptapeptide scaffold
  • PMEH Polymyxin E heptapeptide scaffold
  • Table 4D All compounds were isolated as TFA salts. Compounds D95, D100, D101 , D102, D103, D104, D105, D106, D107, and D1 14 were also prepared as acetate salts. Table 4C - Further Example Compounds
  • the inoculum was prepared by making a direct suspension of isolated colonies (selected from an 18-24 hour Mueller-Hinton agar plate) adjusted to the 0.5 McFarland standard. MIC testing was performed by two-fold serial antibiotic dilutions in cation-adjusted Mueller- Hinton Broth in sterile 96-well microtitre plates in a total volume of 170 ⁇ _ (150 ⁇ _ broth containing the antimicrobial agent, 20 ⁇ _ inoculum). The assays were performed in duplicate. Plates were incubated aerobically without shaking for 18-20 hours at 35 C with the MIC defined as the lowest concentration of drug that prevented visible growth.
  • Table 5C shows the activity, shown by way of MIC values, of Example Compounds in the presence of Rifampicin.
  • MIC values were determined against E. coli and K. pneumoniae in the presence of a fixed concentration (2 g/mL) of Rifampicin, and against A. baumannii in the presence of 0.25 g/mL of rifampicin for the example compounds and the comparator compounds C1 and C2 and CC3.
  • CB-182.804 (C2) is a polymyxin decapeptide derivative with an aryl urea substituent at the N-terminus, which has been claimed to have lower toxicity than Polymyxin B (shown as compound 5 in WO 2010/075416), and was prepared by the present inventors.
  • C1 was also prepared in-house, and corresponds to NAB-739 (as described by Vaara in, for example, WO 2008/017734).
  • CC3 corresponds to compound 5x in Magee et al., J. Med. Chem. 2013, 56, 5079.
  • Table 5D shows the MIC values for Further Example Compounds in the presence of Rifampicin. MIC values were determined against E. coli and K. pneumoniae in the presence of a fixed concentration (2 pg/mL) of Rifampicin, and against A. baumannii in the presence of 0.25 pg/mL of rifampicin.
  • Table 5E shows the MIC values (micrograms/mL) recorded for Further Examples (D50 and D65) and polymyxin each tested in a 1 :1 (wt:wt) combination with Rifampicin.
  • MIC values microgram/mL refer to the total drug concentration (i.e. test agent plus
  • the renal cell toxicity of the compounds was assessed in an in vitro assay using the HK-2 cell line, an immortalized proximal tubule cell line derived from a normal human kidney.
  • the endpoint to describe the toxicity of the compounds was the reduction of resazurin correlating with the metabolic activity of the cells.
  • Cells were cultured in 150 cm 2 flasks in 25 ml_ supplemented KSF (with 5 ng/mL EGF and 50 pg/mL BPE). Cells were maintained at 70% confluence with a maximum of 25 passages.
  • Test compounds were prepared directly into the media, or from stock solutions to result in no more than 0.5% DMSO, or 5% water in the final assay.
  • concentrations were prepared from 1000 pg/mL to 1.95 pg/mL in two-fold dilutions in fresh medium.
  • the microtiter plates were removed from the incubator and the media replaced with 100 pL of the dilutions of the compound solution. Every set of concentration was done in triplicate, and positive and negative controls were added to each plate. The plates were then incubated for 24h at 37 C with 5% CO2 in a humidified atmosphere.
  • Table 6B shows the activity, shown by way of MIC values, of Example Compounds in the absence of a second agent together with the toxicity against the HK-2 cell line
  • MICs were determined as described herein.
  • HK-2 cell I C50 values were determined as described herein. Values are reported relative to Polymyxin B.
  • C2 (CB-182.804) is a polymyxin decapeptide derivative described by Cubist (shown as compound 5 in WO 2010/075416), C1 is NAB-739 (as described by Vaara in, for example, WO 2008/01773).
  • CC3 corresponds to Compound 5x Magee et al, J. Med. Chem., 2013, 56, 5079.

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Abstract

Provided are compounds of formula (III), and the use of compounds of formula (III) in methods of treatment, such as methods of treating a microbial infection. The compounds of formula (III) is: where -R15 is an amino-containing group: and -R1, -R2, -R3, -R4, -R8, -RA, Q, -R16, -R17 are as described in further detail in the description.

Description

POLYMYXIN DERIVATIVES AND THEIR USE IN COMBINATION THERAPY
TOGETHER WITH DIFFERENT ANTIBIOTICS
Related Applications The present case claims priority to, and the benefit of, GB 1404301 .2 filed on 1 1 March 2014 (1 1/03/2014) and GB 1421019.9 filed on 26 November 2014 (26/1 1/2014), the contents of both of which are hereby incorporated by reference in their entirety.
Field of the Invention
The present invention relates to novel compounds, combinations of compounds, pharmaceutical compositions comprising the compounds and the use of the compounds, pharmaceutical compositions and combinations for treatment, for example treatment of microbial infections, particularly those caused by Gram-negative bacteria.
Background
In susceptible individuals, certain Gram-negative bacteria such as Escherichia coli.
Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumanii can cause serious infections, such as pneumonia, urinary tract infections, skin and skin structure infections such as wound infections, ear infections, eye infections, intra-abdominal infections, bacterial overgrowth in the gastrointestinal tract and bacteraemia/sepsis. The treatment of serious bacterial infections in clinical practice can be complicated by antibiotic resistance. Recent years have seen a rise in infections by Gram-negative bacteria which are resistant to many types of antimicrobials including broad spectrum antibiotics such as aminoglycosides, cephalosporins and even carbapenems. There is therefore a need to identify new antimicrobials that are effective against Gram-negative bacteria, in particular against multidrug resistant Gram-negative bacteria. Polymyxins are a class of antibiotics produced by the Gram-positive bacterium Bacillus poly my xa. First identified in the late 1940s, polymyxins, particularly polymyxin B and polymyxin E (colistin, usually as its prodrug colistin methane sulphonate) were used in the treatment of Gram-negative infections. However, these antibiotics exhibited side effects such as neurotoxicity and nephrotoxicity. Nevertheless the polymyxins now play an important role in the therapy of MDR Gram-negative infections due to the lack of viable alternatives. However, their use in therapy is limited to treatment of last resort.
WO 2008/017734 tries to address this toxicity problem by providing polymyxin derivatives carrying at least two but no more than three positive charges. These compounds are said to be effective antibacterial agents with reduced renal toxicity. It is hypothesised in the disclosure that the reduced number of positive charges decreases the affinity of the compound for isolated rat kidney tissue which in turn may lead to a reduction in
nephrotoxicity.
Certain des-fatty acyl polymyxin derivatives have also been disclosed with reduced acute toxicity in mice whilst retaining good activity against pseudomonads (Katsuma et al. Chem. Pharm. Bull. 2009; 57, 332-336; Sato et al. Chem. Pharm. Bull. 201 1 ; 59, 597-602). The compounds were significantly less active than polymyxin B against E. coll and K.
pneumoniae. WO 2010/075416 provides urea linked aryl polymyxin decapeptides including CB182,804, which is reported to have similar activity but reduced renal toxicity compared with polymyxin B. Phenyl cyclopropane polymyxin derivatives are also described in
US 8,415,307. These compounds are shown to have similar or reduced activity compared with polymyxin B.
WO 2012/168820 provides a further series of polymyxin derivatives reported to have reduced toxicity, and sometimes enhanced activity compared with polymyxin B, in which the diaminobutyrate group at position 3 in the tripeptide side chain is replaced by a
diaminopropionate moiety.
There remains a need for less toxic polymyxin derivatives which offer therapeutic preparations with consistently potent activity across the target pathogens and acceptable toxicity. The present inventors have previously described in WO 2013/072695, TW 101 142961 and GCC 2012/22819, the contents of each of which are hereby incorporated in their entirety, polymyxin compounds for use in the treatment of microbial infections.
Surprisingly, the present inventors have found certain polymyxin derivatives which have reduced toxicity compared to polymyxin or colistin and are particularly effective against Gram-negative bacteria.
Summary of the Invention In a general aspect the present invention provides a polymyxin compound of formula (III), as described herein, and its use in a method of treatment or prophylaxis,. The compounds of formula (III) may be used to treat a microbial infection, such as a Gram-negative bacterial infection. In a first aspect of the invention there is provided a polymyxin compound of formula (III), and pharmaceutically acceptable salts, protected forms, solvates and hydrates thereof, such as pharmaceutically acceptable salts, and hydrates thereof. In a second aspect of the invention there is provided a pharmaceutical composition comprising the polymyxin compound of formula (III) together with one or more
pharmaceutically acceptable carriers.
In a third aspect of the invention there is provided a polymyxin compound of formula (III) or a pharmaceutical composition comprising the polymyxin compound of formula (III) for use in a method of treatment of prophylaxis. In a fourth of the invention there is provided a polymyxin compound of formula (III) or a pharmaceutical composition comprising the polymyxin compound of formula (III) for use in a method of treating a bacterial infection.
In an alternative aspect, the compounds of formula (III) or a pharmaceutical composition comprising the polymyxin compound of formula (III) are suitable for use in the treatment of fungal infections.
In a further aspect of the invention there is provided a polymyxin compound of formula (III) for use in a method of treatment or prophylaxis, in combination with an active agent, such as where the active agent has activity against Gram-negative bacteria.
Other aspects of the invention are discussed in detail herein.
Detailed Description of the Invention
The present invention provides compounds of formula (III) and their use in medical treatment.
Broadly, the compounds of formula (III) are polymyxin compounds having an N terminal group that contains amino functionality. In addition to, or as an alternative to, the N terminal group has a nitrogen-containing heterocyclyl (or heterocyclylene) group and/or a
nitrogen-containing heteroalkylene group. The presence of a basic amino group within the terminal group is associated with particular advantages, as discussed in further detail below. The compounds of formula (III) have suitable antibacterial activity whilst also apparently exhibiting less toxicity, especially nephrotoxicity. The compounds may have comparable or improved biological activity compared to Polymyxin B or Colistin against one or more of E, coii, P. aeruginosa, K. pneumonia, or A. baumannii bacterial strains. Such compounds are useful alternatives to the polymyxin type compounds previously described in the art.
Some of the polymyxin compounds or polymyxin derivatives in the art are known or suspected to have a poor toxicity profile. For example, the use of compounds having a fatty acyl chain at the N terminal, such as Polymyxin B and Colistin, is associated with
nephrotoxicity.
Vaara et ai. (Antimicrob. Agents Chemother. 2008, 52, 3229) have suggested that the pharmacological and toxicity properties of a polymyxin compound may be altered with changes to the polymyxin polypeptide sequence. In particular, Vaara ef ai. have prepared a polymyxin compound having only three positive charges, whereas the polymyxin B nonapeptide carries five positive charges. In contrast the present inventors have shown that adaptations to the N terminal of a polymyxin compound may reduce nephrotoxicity. As described herein, the N terminal has a substituent containing an amino group (which may be in the form of a nitrogen-containing heterocycle). Furthermore, the compounds of formula (III) are capable of increasing the antimicrobial activity of a second antimicrobial agent, such as rifampicin. Such combinations have comparable or improved biological activity compared to the combination of the second agent with Polymyxin B or Colistin, for example against one or more of E. coli. P. aeruginosa. K. pneumonia, or A. baumannii strains. For example, compounds of formula (III) may have comparable biological activity compared to Polymyxin B or Colistin against one or more of E. coli, P. aeruginosa, K. pneumonia, or A. baumannii strains. However, when such
compounds are used in combination with a second active agent, the combination has unexpectedly superior activity compared to the combination of Polymyxin B or Colistin with the same active agent. As noted above, the compounds of formula (III) may also posess an inherent antimicrobial activty.
Furthermore, the present inventors have found that each compound of formula (III) is active against a broad range of bacteria and each compound is capable of potentiating the activity of a second active agent, for example against E. coli. P. aeruginosa, K. pneumonia, or A. baumannii strains. In contrast the compounds previously described in the art have a varied profile of biological activity, and it is difficult to predict the extent to which a particular polymyxin compound will potentiate the activity of a second agent.
The compounds of formula (III) have excellent microbial activity whilst also exhibiting less toxicity compared to Polymyxin B or Colistin, for example as measured against HK-2 cells. In some cases the compounds are active even against microbial strains which are resistant or have reduced susceptibility to Polymyxin B and Colistin. The activity is associated with the presence of amino functionality at specific locations within the N terminal group. Further improvements in activity are also found where certain substituents are present in the N terminal group, and the chiral centres in the terminal group have a specific stereochemistry. Polymyxin Compounds of Formula (III)
The compounds of formula (III) are N-terminal derivatives of the polymyxin series of compounds. The core of the compound of formula (III) is a nonapeptide version of a polymyxin compound, such as deacylated polymyxin B nonapeptide (PMBN,
Polymyxin 2-10).
The present inventors have found that the group attached to the N terminal of a polymyxin nonapeptide is an important determinant of biological activity and compound toxicity. The inventors have identified certain N terminal substituent groups that show enhanced activity and/or exhibit less toxicity compared to Polymyxin B or Colistin.
In the polymyxins, the amino acid residue at position 1 is a diamino butyric acid (Dab) residue which is acylated at its N-terminal with a fatty acyl chain. In the compounds of the invention, the N-terminal group of Polymyxin comprising Dab and the fatty acyl chain is replaced by an amine-containing moiety which is linked to a further substituent, but not linked via an amide bond.
Previously, it has been thought that the presence of the Dab amino acid residue at position 1 of Polymyxin B was not important for activity, and this amino acid could be deleted. Thus, polymyxin nonapeptides are known in the art for use in the treatment of microorganisms.
In preliminary work, the present inventors looked at the activity of three polymyxin B analogues against a range of microorganisms. As with other researchers, the inventors found that the deletion of the Dab residue at position 1 in Polymyxin B had little effect on the activity of the compound (compare compounds CC4 and CC6 in Table A below). However, when the inventors looked at a further analogue where the Dab residue was replaced with Gly, a substantial deterioration in biological activity was noted (compare CC5 and CC4). The inventors believe that the presence of amino functionality at the terminal of a polymyxin compound is important for maintaining activity. Thus, the compounds of the invention include amino functionality at the N terminal of a polymyxin compound. The polymyxin B nonapeptide structure is shown below, where -R is a modification of the N terminal group.
PMBN
Figure imgf000007_0001
Table A
Figure imgf000008_0001
where the side chain -R is attached to the N terminal of the Polymyxin B nonapeptide (PMBN), and the data are MIC values at pg/mL
The inventors believe that, for optimal activity, an amino substituent is required to mimic the Dab side chain in the naturally-occurring polymyxin structure. The inventors have therefore provided compounds of formula (I I I) where an amino group -NR16R17 or -N(R16)- is provided at a carbon atom that is β or γ to a group -X- at the N-terminal of a polymyxin nonapeptide. The group -X- may be regarded as equivalent to the carbonyl portion -C(O)- of an amino acid residue at position 1 . The inventors have found that compounds where an amino group is provided solely at a carbon atom that is a to the group -X- have inferior biological activity (compare CC7 with example compounds D4 and D6 in Table B).
Table B
Ex. -R E. coli K. pneumoniae P. aeruginosa A. baumannii
ATCC ATCC
NCTC ATCC A TCC CCUG ATCC NCTC BAA- BAA-
13441 25922 4352 59347 27853 13424
2146 747
CC7 2 1 2 2 1 0.25 8 8
0
D6 rNH2 0.25 0.25 0.5 0.25 0.5 0.25 1 1
Figure imgf000009_0001
where the side chain -R is attached to the N terminal of the Polymyxin B nonapeptide, and the data are MIC values at pg/mL
Compounds where the amine substituent is provided at a carbon atom that is β or γ to the group -X- at the N-terminal of PMBN have been described in WO 2013/072695. However, these compounds, if substituted, have a substituent on the carbon attached to the amine. The inventors have found that it is important that a further substituent is provided, and furthermore that this substituent is not on the carbon attached to the amine (compare B5 and B6 against example compounds D9 and D37 in Table C, where B5 and B6 are Examples 6 and 29 respectively in WO 2013/072695). Accordingly in the compounds of formula (I II) an amino group -NR16R17 or -N(R16)- is connected to a methylene carbon group (-CH2-).
Table C
Figure imgf000009_0002
where the side chain -R is attached to the N terminal of the Polymyxin B
nonapeptide, and the data are MIC values at g/mL. In some instances, the stereochemistry is an important determinant of activity, for example where an additional substituent is provided at the carbon atom that is a to the group -X-. In these instances, it is preferred that the stereochemistry at this position is the same as that of the L-Dab residue in Polymyxin B (compare compound D29 prepared from optically active carboxylic acid with diastereomers D24 and D25 in Table D, where B7 is Example 12 in WO 2013/072695). The data from Table D also shows the importance of a substituent group: compare B7 with D29, for example.
Table D
Figure imgf000010_0001
where the side chain -R is attached to the N terminal of the Polymyxin B
nonapeptide, and the data are MIC values at pg/mL Absolute stereochemistry is depicted by heavy or dashed wedges.
Provided that the amino group remains β- or γ- to the group -X- , the amine group may be part of a nitrogen-containing heterocycle. WO 2013/072695 describes compounds having a nitrogen-containing heterocycle at the N terminal of a nonapeptide. However such compounds are not substituted. The inventors have found that the addition of a substituent improves activity. The compounds of the invention, therefore, where the amine -N(R16)- is part of a ring structure, have a ring substituent (compare B8 with example compounds D2 and D39 in Table E, where B8 is Example 13 from WO 2013/072695). Table E
Figure imgf000011_0001
where the side chain -R is attached to the N terminal of the Polymyxin B nonapeptide, and the data are MIC values at g/mL. The relative stereochemistry is depicted by heavy or dashed lines. Absolute stereochemistry is depicted by heavy or dashed wedges.
The compounds of formula (II I) are characterised over the polymyxin deca peptides for the reason that the compounds of formula (I I I) do not possess the amide functionality of a polymyxin that is formed from the amino group at the a carbon of the L-Dab group at position 1 and the fatty acyl chain. In the compounds of the present invention, where an amino group is provided at the a carbon, it is not part of an amide group.
It is known that polymyxin deca peptide derivatives having a short acyl chain (e.g. butanoyl) connected to the L-Dab residue at position 1 via an amide bond have poor antibacterial activity. For instance the pentanoyl and butanoyl derivatives are reported to be 10-20 times less active than Polymyxin B (see de Visser et al. J. Pept. Res. 2003, 61, 298). Compound D9 (see Table C) has a short isobutyl moiety attached to an aminobutyric acid moiety. It is an analogue of the alkanoyl derivatives described by de Visser, yet it does not include the amide group of those derivatives. Compound D9 has a similar biological activity to the natural polymyxin, and it is 12 times less toxic than polymyxin B (as measured in relation to I C¾ values in a HK-2 assay).
A further example can be seen by comparing example compound D36 with reference compound CC8 (see Table F). Where an amino group is provided at the a carbon, it should not be part of an amide group. Table F
Figure imgf000012_0001
where the side chain -R is attached to the N terminal of the Polymyxin B nonapeptide, and the data are MIC values at pg/mL Absolute stereochemistry is depicted by heavy or dashed wedges.
As noted above, the presence of an amino group solely at the a carbon is not sufficient to provide good activity. An amino group at a β or γ carbon is required. Where an amino group, such as -NR16R17 or -N(R16)- is provided at the β or γ carbon, a further substituted amino group may be provided at the a carbon (and this amino group does not form part of an amide bond). Such compounds have good activity. This is seen in compound D51 , whose activity is comparable to Polymyxin B (Table G). Table G
Figure imgf000012_0002
where the side chain -R is attached to the N terminal of the Polymyxin B nonapeptide, and the data are MIC values at pg/mL The present invention provides a compound of formula (III) and the use of this compound in a method of treatment. The compound of formula (III) is represented thus:
Figure imgf000013_0001
wherein:
-X- represents -C(O)-, -NHC(O)-, -OC(O)-, -CH2- or -SO2-;
-R1 together with the carbonyl group and nitrogen alpha to the carbon to which it is
attached, is a phenylalanine, leucine or valine residue;
-R2 together with the carbonyl group and nitrogen alpha to the carbon to which it is
attached, is a leucine, iso-leucine, phenylalanine, threonine, valine or nor-valine residue;
-R3 together with the carbonyl group and nitrogen alpha to the carbon to which it is
attached, is a threonine or leucine residue;
-R4 is C1-6 a Iky I substituted with one hydroxyl group or one amino group;
-R15 is an amino-containing group:
Figure imgf000013_0002
where:
-RA is hydrogen or -LA-RM;
-Q- is a covalent bond or -CH(RB)-;
-RB is hydrogen or -LB-RBB; or, where -Q- is -CH(RB)-, -RA and -RB together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or -RA and -RB together form a 5- to 10-membered monocyclic or bicyclic heterocycle; and, where -Q- is a covalent bond, -RA is -LA- ^, and where -Q- is -CH(RB)- one or both of -RA and -RB is not hydrogen; -R16 is independently hydrogen or C1-4 alkyl;
-R17 is independently hydrogen or C1-4 alkyl;
or -NR16R17 is a guanidine group;
or -R1 and -RA together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle;
or, where -Q- is -CH(RB)-, -R17 and -RB together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle; and where -R17 and -RA together form a monocyclic nitrogen-containing heterocycle, each ring carbon atom in -R17 and -RA is optionally mono- or di-substituted with -Rc, and the monocyclic heterocycle is substituted with at least one group selected from -Rc, -RN, -RNA and -LB-RBB, where present,
and where -R17 and -RB together form a monocyclic nitrogen-containing heterocycle, each ring carbon atom in -R17 and -RB is optionally mono- or di- substituted with -Rc, and the monocyclic heterocycle is substituted with at least one group selected from -Rc, and -RN, where present, or the monocyclic heterocycle is optionally substituted when -RA is -LA-RAA,
and a monocyclic nitrogen-containing heterocycle optionally contains one further nitrogen, oxygen or sulfur ring atom, and where a further nitrogen ring atom is present it is optionally substituted with -RN, with the exception of a further nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; where -R17 and -RA or -R17 and -RB together form a bicyclic nitrogen- containing heterocycle, each ring carbon atom in -R17 and -RA or -R17 and -RB is optionally mono- or di-substituted with -RD;
and the bicyclic nitrogen-containing ring atom heterocycle optionally contains one, two or three further heteroatoms, where each heteroatom is independently selected from the group consisting of nitrogen, oxygen and sulfur, and where further nitrogen ring atoms are present, each further nitrogen ring atom is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; where -RA and -RB together form a 5- to 10-membered monocyclic carbocycle or heterocycle, each ring carbon atom in -RA and -RB is optionally mono- or di-substituted with -Rc, and a nitrogen ring atom, where present in the monocyclic heterocycle, is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; where -RA and -RB together form a 5- to 10-membered bicyclic carbocycle or heterocycie, each ring carbon atom in -RA and -RB is optionally mono- or
di-substituted with -RD, and a nitrogen ring atom, where present in the bicyclic heterocycie, is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; and where R17 and -RA or -R17 and -RB together form a 5- to 10-membered nitrogen- containing monocyclic or bicyclic heterocycie, or where -RA and -RB together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or together form a 5- to 10-membered monocyclic or bicyclic heterocycie, a carbon ring atom in -R17 and -RA, -R17 and -RB, or -RA and -RB is optionally alternatively substituted with oxo (=0); each -Rc is independently -Lc-Rcc;
each -RD is independently selected from -Rc, -NO2, halo, -OH, and -N H2; each -RN is independently -LN-RNN;
each -RNA is independently -RL-RNN or -RNN:
-RAA, -RBB, and each -Rcc and -RNN where present, is independently selected from C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, and C5-12 aryl; each -LA- is independently a covalent bond or a linking group selected from -RL-*, -0-LAA-\ -N(R11)-LAA-*, and -0(0)-^-*, where the asterisk indicates the point of attachment of the group -LA- to -RM; each -LB- and -Lc- is independently a covalent bond or a linking group selected from -RL-*, -0-LAA-*, -OCCO^L^^ CR11 )-^-*, -N(R11)C(0)-LAA-*, -C{0)-LM-*, -C(0)0-LAA-*, and -C(0)N(R11)- LAA-*, and optionally further selected from -N(R 1)S(0)-LAA-*,
-N(R1 1)S(0)2-LAA-*, -S(0)N(R11)-LAA-*, and -S(0)2N(R1 1)-LAA-* where the asterisk indicates the point of attachment of the group -LB- to -RBB or the group -Lc- to -Rcc; each -LN- is independently a covalent bond or a group selected from -S(0)-LAA-*, -S^-L^-*, -C(0)-LAA-* and -C(0)N(R1 )-LAA-*, where the asterisk indicates the point of attachment of the group -LN- to -RNN; and each -L^- is independently a covalent bond or -R1 -; and each -RL- is independently selected from C1-12 alkylene, C2-12 heteroalkylene, C3-10 cycloalkylene and C5-10 heterocyclylene, and where -L^- is connected to a group C1-12 alkyl, -RL- is not C1-12 alkylene; and each C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, C5-12 aryl, C1-12 alkylene, C2-12 heteroalkylene, C3-10 cycloalkylene and C5-10 heterocyclylene group is optionally substituted, where -Rs is an optional substituent to carbon and -R12 is an optional substituent to nitrogen; each -Rs is independently selected from -OH, -OR12, -OC(0)R12, halo, -R12, -NHR12, -NR12R13, -NHC(0)R12, -N(R12)C(0)R12, -SH, -SR12, -C(0)R12, -C(0)OH, -C(0)OR12, -C(0)NH2, -C(0)NHR12 and C(0)NR1 R13; except that -R12 is not a substituent to a C1-12 alkyl group; or where a carbon atom is di-substituted with -Rs, these groups may together with the carbon to which they are attached form a C3-6 carbocycle or a C5-6 heterocycle, where the carbocycle and the heterocycle are optionally substituted with one or more groups -R12; each -R12 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl;
each -R13 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl;
or -R12 and -R13, where attached to N, may together form a 5- or 6-membered heterocyclic ring, which is optionally substituted with C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl; each -R1 1 is independently hydrogen or C1-4 alkyl; and
-R8 is hydrogen or methyl, and pharmaceutically acceptable salts, protected forms, solvates and hydrates thereof, such as pharmaceutically acceptable salts, and hydrates thereof..
In one embodiment, -X- is -C(O)-.
In one embodiment, the carbon atom in R15 that is a to the group -X- is part of a methine (-CH-) group i.e. -RA is not hydrogen.
In one embodiment, the carbon atom in R15 that is β to the group -X- is part of a methine (-CH-) group i.e. -RB is not hydrogen.
In one embodiment, the carbon atom in R15 that is β to the group -X- is part of a methylene group. Thus, where -Q- is present, -RB is hydrogen.
When -Q- is a covalent bond, the carbon atom in R15 that is β to the group -X- (the carbon in -CHi>N R16R1 /) is always part of a methylene group.
In one embodiment, the compound is in salt form, for example the compound is an acetate salt.
In one embodiment, the compound is in protected from, for example where amino and hydroxy I functionality is protected. Polymyxin B
Polymyxin B nonapeptide has the structure shown below: H2N-Thr2-Dab-Dab4-Dab-D-Phe-Leu-Dab-Dab-Thr10 where positions 2, 4 and 10 are indicated (with reference to the numbering system used for the Polymyxin B deca peptide), and the amino acid residues are in the
L-configuration, unless indicated.
The compounds of the invention are derivatives of polymyxin B nonapeptide , where (i) the N terminal amino group, -Nh , is replaced with the group -NH-A-X-R6 or -NH-X-R15 as described herein and optionally (ii) the amino acid residues at 2, 3, 6, 7 and 10 positions are substituted with another amino acid residue.
For convenience, the compounds of the invention are represented by the formula (III) where the amino acids at positions 2, 3. 6, 7 or 10 are determined by the nature of the groups R8, R4, R1, R2 and R3 respectively. Compounds of the invention, which include the variants described above, are biologically active.
A variant of the compound is a compound in which one or more, for example, from 1 to 5, such as 1. 2. 3 or 4 amino acids are substituted by another amino acid. The amino acid may be at a position selected from positions 2, 3, 6. 7 or 10 (referring to the numbering of residues used in polymyxin B). The substitution may be for another amino acid or for a stereoisomer.
Set out below are various embodiments that apply to the compounds of formula (III). The embodiments are combinable, in any combination. -Q-
In one embodiment, -Q- is a covalent bond.
In one embodiment, -Q- is -CH(RB)-. In this embodiment, -RB may be a group -LA-RBB, or -RB together with -R17 may form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle, as described in further detail below.
Where -R1/ and -RA together form a nitrogen-containing heterocycle, the group -Q- is preferably a covalent bond. In one embodiment, -Q- is -CH(RB)-, and forms part of a nitrogen-containing heterocycle. In this embodiment, -RB may be hydrogen. -R16 and -R17
In one embodiment, -R16 Is hydrogen.
In one embodiment, -R16 is C1-4 alkyl, such as methyl, ethyl or propyl, such as methyl.
In one embodiment, -R17 is hydrogen.
In one embodiment, -R17 is C1-4 alkyl, such as methyl, ethyl or propyl, such as methyl.
In one embodiment, -R17 and -RA together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle. In one embodiment, -R17 and -RB together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle. This is discussed in further detail below.
In one embodiment, -R16 is not ethyl when -R17 is hydrogen, methyl or ethyl.
In one embodiment, -R16 is not methyl when -R17 is hydrogen, methyl or ethyl. In one embodiment, -R16 is hydrogen and -R17 is hydrogen.
In one embodiment, -NR16R17 is not a guanidine group.
Nitrogen-Containing Heterocycle The groups -R17 and -RA may, together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle. Similarly, -R17 and -RB may, together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle. The nitrogen in the nitrogen-containing heterocycle refers to the nitrogen atom in -N(R16)-. The nitrogen-containing heterocycle may be a monocyclic or bicyciic nitrogen-containing heterocycle. A bicyciic nitrogen-containing heterocycle has two fused rings.
The nitrogen-containing heterocycle contains a total of 5 to 10 ring atoms. Where the nitrogen-containing heterocycle is monocyclic it may have 5 to 7 ring atoms, for example 5 to 6, such as 6, ring atoms. Where the nitrogen-containing heterocycle is bicyciic it may have 8 to 10 ring atoms, such as 9 to 10, such as 10, ring atoms. Each ring in the bicyciic heterocycle may have 5 to 7 ring atoms, for example 5 or 6, such as 6, ring atoms.
Where the nitrogen-containing heterocycle is bicyciic, one ring may be aromatic or partially unsaturated. The ring that is formed together with the carbon atoms a and β to the group -X- (the first ring) is not aromatic. It is the second ring, which is the ring fused to the first, that may be aromatic. The first ring is saturated, except for the carbon ring atoms that are shared with the second ring (bridge atoms), which may be may be part of the aromatic ring system of the second ring, for example. Where the nitrogen-containing heterocycle is monocyclic, each carbon ring atom in -R17 and -RA or each carbon ring atom in -R17 and -RB is optionally mono- or di-substituted with -Rc. Where the nitrogen-containing heterocycle is bicyclic, each carbon ring atom in -R17 and -RA or each carbon ring atom in -R17 and -RB is optionally mono- or di-substituted with -RD, as appropriate. A carbon ring atom may be unsubstituted or mono-substituted with -RD if that carbon ring atom is part of an aromatic ring system, or is part of an unsaturated bond.
The group -RD includes the group -Rc. In one embodiment, where the nitrogen-containing heterocycle is bicyclic, each carbon ring atom in the second ring is optionally mono-or di-substituted with -RD and each carbon ring atom in the first ring in is optionally mono-or di-substituted with -Rc.
In one embodiment, the nitrogen-containing heterocycle is a monocyclic nitrogen-containing heterocycle.
In one embodiment, the nitrogen-containing heterocycle is a bicyclic nitrogen-containing heterocycle.
In one embodiment, one carbon ring atom in the nitrogen-containing heterocycle is mono- or di-substituted, such as mono-substituted, with -Rc or substituted with -LB-RBB, where present, for example mono-substituted with -Rc. In one embodiment, one carbon ring atom in -R17 and -RA or -R17 and -RB is mono- or di-substituted, such as mono-substituted, with - Rc, for example -LA-RCC. In these embodiments, the remaining carbon atoms in the nitrogen-containing heterocycle are unsubstituted. This embodiment is preferred when the nitrogen-containing heterocycle is monocyclic.
Where the nitrogen-containing heterocycle is bicyclic, each carbon ring atom in the nitrogen- containing heterocycle may be unsubstituted. Alternatively, where the nitrogen heterocycle is bicyclic one carbon ring atom in the nitrogen-containing heterocycle may be mono- or di-substituted, such as mono-substituted, with -Rc or -LB-RBB, such as with -Rc. For example, where the nitrogen heterocycle is bicyclic one carbon ring atom in -R17 and -RA or -R17 and -RB is mono- or di- substituted, such as mono-substituted, with -Rc, for example -LA-RCC. In these embodiments, the remaining carbon atoms in the nitrogen-containing heterocycle are unsubstituted.
The nitrogen-containing heterocycle may contain further hetero ring atoms independently selected from nitrogen, oxygen and sulfur. Where the nitrogen-containing heterocycle is a monocyclic, the heterocycle optionally contains one further nitrogen, oxygen or sulfur ring atom. Where the nitrogen-containing heterocycle is a bicyclic nitrogen-containing
heterocycle, the heterocycle optionally contains one, two or three further heteroatoms, where each heteroatom is independently selected from the group consisting of nitrogen, oxygen and sulfur. In a bicyclic system, the further heteroatoms atoms may be provided in the first or second rings, such as the first ring.
In one embodiment, where a further heteroatom is provided, that heteroatom is nitrogen. In one embodiment, one further heteroatom is provided, such as one further nitrogen heteroatom.
In one embodiment, the nitrogen-containing heterocycle does not contain a further heteroatom.
Where two heteroatoms are provided in a ring, they are not separated by an unsubstituted methylene group (-CH2-) or a mono-substituted methylene group (e.g. -CH(RC)-), and optionally they are not separated by a di-substituted methylene group (e.g. -C(RC)2-). Where reference is made to a further nitrogen ring atom, the ring atom may be provided as a group -NH-, and the nitrogen atom may be optionally substituted with -RN or -RNA, as appropriate. A further nitrogen ring atom may be unsubstituted if it is part of an aromatic ring system, or is part of an unsaturated bond. Where reference is made to a further sulfur ring atom, the sulfur ring atom may be provided as -S-, -S(O)- or -S(0)2-, such as -S-.
Each further nitrogen ring atom is optionally substituted with a group -RN, as appropriate, with the exception of a further nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA. This is shown schematically below for two exemplary R15-X- groups comprising monocyclic heterocycles containing a further nitrogen ring atom:
Figure imgf000020_0001
where the ring system on the right has a nitrogen ring atom that is connected to the carbon atom that is a to the group -X-. Such a nitrogen atom is optionally substituted with -RNA, and is shown substituted with -RNA. The ring system on the left has a nitrogen ring atom that is not connected to the carbon atom that is a to the group -X- (it is attached to a carbon β to the group -X-). Such a nitrogen atom is optionally substituted with -RN, and is shown substituted with -RN. In the exemplary ring structures shown above the carbon ring atoms are shown to be unsubstituted. As described herein, carbon ring atoms that are present in -R17 and -RA are optionally mono- or di-substituted.
It is noted that the definitions for -RNA do not encompass groups that would together with the further nitrogen ring atom form an amide group.
When a second ring is present and that second ring is an aromatic ring containing one or more further nitrogen atoms, a nitrogen atom in the aromatic ring may not be substituted with a group -RN, as appropriate. Where a further nitrogen ring atom is substituted with -RN or -RNA, as appropriate, each carbon ring atom in the nitrogen-containing heterocycle may be unsubstituted. Where -R1 and -RA together form a monocyclic nitrogen-containing heterocycle, the heterocycle is substituted with at least one group selected from -Rc, and -RN, -RNA and -LB-RBB i.e. at least one of these groups must be present as a ring substituent at the appropriate position. Thus, in this embodiment, where the nitrogen-containing heterocycle is monocyclic and does not contain a further nitrogen atom, at least one carbon ring atom must be substituted with -Rc or -LB-RBB, where present. Further, in this embodiment, where the nitrogen-containing heterocycle is monocyclic and contains a further nitrogen atom, and that nitrogen atom is unsubstituted, at least one carbon ring atom must be substituted with -Rc or -LB-RBB, where present. If a further nitrogen atom in the monocyclic nitrogen-containing heterocycle is substituted with a group -RN or -RNA, the carbon ring atoms may be
unsubstituted or optionally mono- or di-substituted.
Where -R1 / and -RB together form a monocyclic nitrogen-containing heterocycle, the heterocycle is substituted with at least one group selected from -Rc, and -RN, where present. Alternatively the heterocycle is optionally substituted if -RA is -L R^. In one embodiment, the monocyclic nitrogen-containing heterocycle is unsubstituted when the group -RA is -LA-
R .
If -RA is hydrogen, the monocyclic nitrogen-containing heterocycle must be substituted with at least one group selected from -Rc, and -RN, where present. Here, if the nitrogen- containing heterocycle is monocyclic and does not contain a further nitrogen atom, at least one carbon ring atom must be substituted with -Rc. Further, in this embodiment, where the nitrogen-containing heterocycle is monocyclic and contains a further nitrogen atom, and that nitrogen atom is unsubstituted, at least one carbon ring atom must be substituted with -Rc. If a further nitrogen atom in the monocyclic nitrogen-containing heterocycle is substituted with a group -RN, the carbon ring atoms may be unsubstituted or optionally mono- or di- substituted.
Where a nitrogen-containing heterocycle is bicyclic, each further nitrogen ring atom may be unsubstituted. Alternatively, where the nitrogen heterocycle is bicyclic one further nitrogen ring atom may be substituted with a group -RN, except where the further nitrogen ring atom is connected to the carbon that is a to the group -X-, that further nitrogen ring atom is substituted with a group -RNA.
In one embodiment, a monocyclic nitrogen-containing heterocycle is mono-substituted with -Rc. Thus, one carbon ring atom in the group -R17 and -RA or -R17 and -RB is
mono-substituted with -Rc.
In one embodiment, a monocyclic nitrogen-containing heterocycle containing a further nitrogen ring atom is mono-substituted with a group -Rc, -RN or -RNA, for example mono-substituted with a group -RN or -RNA or mono-substituted with a group -Rc. Thus, one ring atom in the group -R 7 and -RA or -R17 and -RB is mono-substituted.
The nitrogen-containing heterocycie may be selected from the group consisting of pyrrolidine, piperidine, piperazine, 1.4-diazepine, indoline, 1 ,2,3,4-tetrahydroquinoline, 1 ,2,3,4-tetrahydroisoquinoline, 1 ,2,3,4-tetrahydroquinoxaline, 1 ,2,3,4,6,7.8,8a- octahydropyrrolo[1 ,2-a]pyrazine, 1.2.3,4-tetrahydropyrrolo[1 ,2-a]pyrazine, 5.6,7,8-tetrahydro- 1 ,6-naphthyridine and 1 ,2,3,4-tetrahydro-2,6-naphthyridine. In the bicyclic systems the aromatic ring, where present, is provided as the second ring.
The monocyclic nitrogen-containing heterocycles pyrrolidine, piperidine, piperazine, and 1 ,4-diazepine are substituted as discussed above.
The bicyclic nitrogen-containing heterocycles indoline, 1 ,2,3,4-tetrahydroquinoline,
1.2,3,4-tetrahydroisoquinoline and 1 ,2,3,4-tetrahydroquinoxaline may be substituted or unsubstituted, as discussed above.
A nitrogen-containing heterocycie may be selected from the group consisting of pyrrolidine, piperidine, piperazine, and 1 ,4-diazepine.
In one embodiment, a nitrogen-containing heterocycie is selected from pyrrolidine, piperidine and piperazine.
In one embodiment, a bicyclic nitrogen-containing heterocycie has a first ring selected from pyrrolidine, piperidine and piperazine fused to a second ring, which may be an aromatic ring. Examples of the second ring include cyclohexane, benzene and pyridine ring
In one embodiment, the groups -R17 and -RA together form a nitrogen heterocycie when -CD- is a covalent bond. Here, the group -NR16- is located on a carbon atom that is β to the group -X-.
In another embodiment, the groups -R17 and -RA together form a nitrogen heterocycie when -Q- is not a covalent bond. Here, the group -NR16- is located on a carbon atom that is γ to the group -X-.
In one embodiment, -R17 and -RA are selected from *-CH(Rc1)CH(Rc1)CH(RC1)-,
*-CH(Rc1)CH(RC1)-, and *-N(RNA)CH(Rc1 )CH(RC1)- where * indicates the point of attachment to the carbon a to the group -X-, -RC1 is hydrogen or -Rc, and at least one carbon or nitrogen atom is substituted with -Rc or -RNA, as appropriate.
Exemplary nitrogen-containing heterocycie structures are given in the -R15 section below. Carbocycle and Heterocycle
In one embodiment, -RA and -RB together form a 5- to 10-membered carbocycle or heterocycle. Here, -Q- is not a covalent bond. The carbocycle or heterocycle may be substituted or unsubstituted.
A carbocycle or a heterocycle may be monocyclic or bicyclic. A bicyclic carbocycle or a heterocycle has two fused rings.
The carbocycle or a heterocycle contains a total of 5 to 10 ring atoms. Where the carbocycle or heterocycle is monocyclic it may have 5 to 7 ring atoms, for example 5 to 6, such as 6, ring atoms. Where the carbocycle or heterocycle is bicyclic it may have 8 to 10 ring atoms, such as 9 to 10, such as 10, ring atoms. Each ring in the bicyclic system may have 5 to 7 ring atoms, for example 5 or 6, such as 6, ring atoms. Where the carbocycle or heterocycle is bicyclic, one ring may be aromatic or partially unsaturated. The ring that is formed together with the carbon atoms a and β to the group -X- (the first ring) is not aromatic. It is the second ring, which is the ring fused to the first, that may be aromatic. The first ring is saturated, except for the carbon ring atoms that are shared with the second ring (bridge atoms), which may be may be part of the aromatic ring system of the second ring.
A bicyclic heterocycle is a heterocycle having a heteroatom, such as N, S, or O in either the first or second ring.
In one embodiment, a heteroatom is present in the first ring. In one embodiment, a heteroatom is present in the second ring.
The heterocycle includes one or more heteroatoms independently selected from N, S, and O. In one embodiment heterocycle includes one or two, such as one heteroatom.
In one embodiment, the heteroatom is nitrogen.
In one embodiment, one heteroatom present, such as one nitrogen heteroatom.
Where the carbocycle or a heterocycle is monocyclic, each carbon ring atom in -RA and -RB is optionally mono- or di-substituted with -Rc.
Where the carbocycle or a heterocycle is bicyclic, each carbon ring atom in -RA and -RB is optionally mono- or di-substituted with -RD, which includes -Rc.
Where reference is made to a nitrogen ring atom, the ring atom may be provided as a group -NH-, and the nitrogen atom may be optionally substituted with -RN or -RNA, as appropriate. A further nitrogen ring atom may be unsubstituted if it is part of an aromatic ring system, or is part of an unsaturated bond. Where reference is made to a sulfur ring atom in the heterocycle, the sulfur ring atom may be provided as -S-, -S(O)- or -S(0)2-, such as -S-.
In one embodiment, one carbon ring atom in the carbocycle or heterocycle is mono- or di-substituted, such as mono-substituted, with -Rc or -RD, where appropriate. In this embodiment, the remaining carbon atoms in the carbocycle or heterocycle may be unsubstituted. This embodiment is preferred when the carbocycle or heterocycle is monocyclic. In one embodiment, the heterocycle has a nitrogen ring atom and that atom is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA. In one embodiment, where a nitrogen ring atom is present in the heterocycle, that ring atom may be substituted. In this embodiment, the remaining carbon atoms in the carbocycle or heterocycle may be unsubstituted. This embodiment is preferred when the heterocycle is monocyclic.
It is noted that the definitions for -RNA do not encompass groups that would together with a nitrogen ring atom form an amide group.
When a second ring is present and that second ring is an aromatic ring containing one or more nitrogen atoms, a nitrogen atom in the aromatic ring may be substituted with a group - RN, as appropriate.
In one embodiment, a monocyclic carbocycle is selected from cyclohexane and
cyclopentane, which may be substituted as discussed above.
In one embodiment, a monocyclic heterocycle is selected from pyrrolidine, tetrahydrofuran, tetrahydrothiophene, piperidine, piperazine, 1 ,4-dioxane, morpholine, thiomorpholine and 1 ,4-diazepine, which may be substituted as discussed above. In one embodiment, a monocyclic carbocycle is selected from indane and tetralin.
In one embodiment, a bicyclic heterocycle is selected from indoline,
1 ,2,3,4-tetrahydroquinoline, 1 ,2,3,4-tetrahydroisoquinoline, 1 ,2.3,4-tetrahydroquinoxaline, chromane, and dihydrobenzofuran, which may be substituted as discussed above. -R15
The group -R15 together with -X- may be regarded as an N terminal substituent group in the compounds of formula (III). -R15 contains an amino group which may be a group -NR16R17, or a group -NR16- where the nitrogen is present as a ring atom in a nitrogen-containing heterocycle. In the compounds of the invention, the nitrogen group -NR16R17 must be bonded to one methylene group (i.e. a group -CH2-). Thus, -R15 must contain a group -CH2NR16R17.
When the nitrogen group -NR16- is provided in a nitrogen-containing heterocycle (i.e. -R 7 and -RA form a ring, or -R17 and -RBform a ring), the nitrogen atom must be bonded to one neighboring carbon atom that is part of a methylene group. This is a requirement for the group -R15. However, the other neighboring ring carbon atom is not necessarily part of a methylene group (it may be a methylene or methine group). In one embodiment, the nitrogen atom in -NR16- is bonded to two ring methylene groups (i.e. both neighboring ring carbon atoms are provided in methylene groups). In one embodiment, the nitrogen atom in - NR16- is bonded to a carbon ring atom that is part of a methylene group and a carbon ring atom that is part of a methylene or methine group.
In one embodiment, -R15 is selected from the groups listed below. The groups shown below include groups where -R1 7 and -RA together form a nitrogen-containing heterocycle.
In the embodiments below -RC1 is hydrogen or -Rc; -RN1 is hydrogen or -RNA; -RD1 is hydrogen or -RD; -RA is hydrogen or -LAR^; -RB is hydrogen or -LB-RBB; and -R16 is independently hydrogen or C1-4 alkyl; -R17 is independently hydrogen or C1.4 alkyl; or -NR16R17 is a guanidine group. As noted above, where -Q- is a covalent bond -RA is -|_A-RAA, and where -Q- is -CH(RB)- one or both of -RA and -RB is not hydrogen. Where the nitrogen- containing heterocycle is monocyclic, it should be substituted with at least one group selected from -Rc, and -LB-RBB, -RNA and -RN. In one embodiment, -R15 is selected from the roup consisting of:
Figure imgf000025_0001
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000026_0001
In one embodiment, -R15 is selected from the roup consisting of:
Figure imgf000026_0002
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000026_0003
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000026_0004
embodiment, -R15 is selected from the group consisting of:
Figure imgf000026_0005
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000027_0001
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000027_0002
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000027_0003
In one embodiment, -R15 is selected from the roup cons
Figure imgf000027_0004
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000027_0005
In one embodiment, -R15 is selected from the group consisting of:
Figure imgf000027_0006
In one embodiment, -R15 is:
Figure imgf000028_0001
In one embodiment, -R15 is:
Figure imgf000028_0002
In one embodiment, -R15 is:
Figure imgf000028_0003
Figure imgf000028_0004
In one embod 15 is:
Figure imgf000029_0001
The structures shown above include examples where -R16 contains a nitrogen-containing heterocycie. These are compounds where the groups -R17 and -RA, together with the carbon atoms to which they are attached, form a nitrogen heterocycie. The nitrogen heterocycles shown above are monocyclic nitrogen heterocycles.
Each carbon ring atom in the group -R17 and -RA may be substituted with -RC1. Where -RC1 is hydrogen, the carbon ring atom is unsubstituted.
A nitrogen ring atom in the group -R17 and -RA, where present, is substituted with -RN1. Where -RN1 is hydrogen, the nitrogen ring atom is unsubstituted.
Where the nitrogen-containing heterocycie contains a further nitrogen atom, it is preferred that the further nitrogen atom is substituted with -RN or -RNA, as appropriate. In this embodiment, the ring carbon atoms may be unsubstituted. Where the nitrogen-containing heterocycie does not contain a further nitrogen atom, one of the carbon ring atoms is substituted with -Rc or -LB-RBB, and preferably one of the carbon ring atoms group -R17 and -RA is substituted with -Rc.
The compounds of the invention also include compounds where -R17 and -RA, together with the carbon atoms to which they are attached, form a bicyclic nitrogen heterocycie. In this embodiment, it is not necessary for the carbon or nitrogen ring atoms in -R17 and -RA to be substituted (i.e. each of -RD and -RN may be hydrogen).
Additionally or alternatively to the -R15 groups shown above, -R15 is selected from:
Figure imgf000030_0001
Additionally or alternatively to the -R15 groups shown above, -R15 is selected from:
Figure imgf000030_0002
Additionally or alternatively to the -R15 groups shown above, in one embodiment -R15 is selected from:
Figure imgf000030_0003
In one embodiment, -RA and -RB may together form a carbocycle or a heterocycle. The ring atoms of the carbocycle or heterocycle may be optionally substituted. A carbon ring atom may be optionally mono- or di-substituted with -Rc. A nitrogen ring atom, where present, may be optionally substituted with -RN, except that a nitrogen ring atom that is connected to the carbon that is a to the group -X- is optionally substituted with -RNA.
In the embodiments below -RC1 is hydrogen or -Rc; -RN1 is hydrogen or -RNA; -RD1 is hydrogen or -RD; and -R16 is independently hydrogen or C i alkyl; -R17 is independently hydrogen or C alkyl; or -NR16R17 is a guanidine group. Where the nitrogen-containing carbocycle heterocycle is monocyclic, it is optionally substituted with at least one group selected from -Rc, and -RNA and -RN. Additionally or alternatively to the -R15 groups shown above, in one embodiment -R16 is selected fro
Figure imgf000031_0001
Additionally or alternatively to the -R15 groups shown above, in one embodiment -R15 selected fro
Figure imgf000031_0002
-RA
In one embodiment, -RA is not hydrogen. In one embodiment, -RA is -LA-RAA. In one embodiment, -RA is -RAA. In these embodiments, -RB, if present, may be hydrogen. In one embodiment, where -RA is not hydrogen, for example where -RA is -LA-R^ or -RA and -R17 together form a nitrogen-containing heterocycle, -R15 is an amino-containing group:
Figure imgf000032_0001
Where -RA is -L R** it is noted that this group does not encompass a substituent containing the group -C(0)N(R11)-*, where the asterisk indicates the point of attachment to the carbon that is a to the group -X-. The inventors have found that where the group -C(0)N(R11)-* is present, biological activity is reduced. In one embodiment, -RA and -R17 together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle.
In one embodiment, -RA and -RB together form a 5- to 10-membered carbocycle or heterocycle. Here, -Q- is not a covalent bond.
In one embodiment, -RA is not -NHEt or -NE , for example where R15-X- is an N terminal substituent to Polymyxin B nonapeptide (PMBN).
In one embodiment, -RA is not -NHRPA or -N(RPA)2, where each -RPA is C1-10 alkyl, such as Cs-10 alkyl, such as Ci-8 alkyl, such as C1-1 alkyl, such as C1-2 alkyl, for example where R15-X- is an N terminal substituent to Polymyxin B nonapeptide (PMBN).
In one embodiment, -RA is not a group having an oxygen atom attached to the carbon that is a to the group -X-. In one embodiment, -RA is not a group having a nitrogen atom attached to the carbon that is a to the group -X-. The definitions for the group -LA-R^ may be construed accordingly.
-RB In one embodiment, -RB, where present, is hydrogen. In one embodiment, -Q- is a covalent bond and -RB is accordingly absent.
In one embodiment, -RB is -LA-RBB. In one embodiment, -RB is -RBB. In these embodiments, -RA may be hydrogen. In one embodiment, -RB is not C3-10 cycloalkyl, for example is not cyclohexyl.
In one embodiment, -RB and -R17 together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle. In one embodiment, -RA and -RB together form a 5- to 10-membered carbocycle or heterocycle. Here, -Q- is not a covalent bond.
Where -Q- is present and is part of a nitrogen-containing heterocycle and -RB is -LA-RBB, the nitrogen-containing heterocycle is optionally substituted. Thus each carbon ring atom in -RB and -R1 / is optionally substituted with -Rc, and each nitrogen ring atom in -RB and -R17 is optionally substituted with -RN.
In one embodiment one of -RA and -RB is hydrogen. The other of -RA and -RB is therefore not hydrogen.
It is noted that the group -LB-RBB encompasses a substituent containing the group
-C(0)N(R11)-*, where the asterisk indicates the point of attachment to the carbon that is β to the group -X-.
-Rc, -RN and -RNA
The groups -RA and -R17 or -RB and -R17 may together form a 5- to 10-membered nitrogen- containing monocyclic or bicyclic heterocycle, and -RA and -RB may together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or together form a 5- to 10-monocyclic or bicyclic heterocycle. The ring atoms that are present in the nitrogen-containing heterocycle and the carbocycle or heterocycle may be substituted or unsubstituted as described herein.
The nitrogen-containing heterocycle includes ring atoms that are part of -RA and -R17 or -RB and -R17. Where -RA and -R or -RB and -R17 form a nitrogen-containing monocyclic or bicyclic heterocycle, each carbon ring atom in the group -RA and -R17 or the group -RB and -R17 may be optionally substituted with -Rc. These carbon ring atoms may be mono- or di-substituted with -Rc . In one embodiment, each carbon ring atom is optionally mono- substituted with -Rc.
As described herein a nitrogen-containing monocyclic heterocycle must be substituted. The substituent may be present as a substituent to a ring atom that is part of -RA and -R17 or -RB and -R17. Thus, a group -Rc, -RN or -RNA, where appropriate, is present. Alternatively the substituent may be present at the carbon to the group -X- i.e. -LB-RBB is present.
The nitrogen-containing heterocycle may contain further nitrogen ring atoms. Each further nitrogen ring atom may be optionally substituted with -RN, as appropriate. However, where the further nitrogen atom is bonded to the carbon that is a to the group -X-, that ring nitrogen atom is optionally substituted with -RNA.
In one embodiment, -RA and -RB together form a 5- to 10-membered monocyclic or bicyclic carbocycle or heterocycle. In the monocycle, each ring carbon atom in -RA and -RB is optionally mono- or di-substituted with -Rc. These carbon ring atoms may be mono- or di-substituted with -Rc. In one embodiment, each carbon ring atom is optionally mono- substituted with -Rc. In the bicycle, each ring carbon atom in -RA and -RB is optionally mono- or di-substituted with -RD. These carbon ring atoms may be mono- or di-substituted with -RD.
A 5- to 10-membered monocyclic or bicyclic heterocycle may contain a nitrogen ring atom. Each nitrogen ring atom may be optionally substituted with -RN, as appropriate. However, where the further nitrogen atom is bonded to the carbon that is a to the group -X-, that ring nitrogen atom is optionally substituted with -RNA.
One of the carbon ring atoms that is part of -RA and -R1 , -RB and -R17, or -RA and -RB may be substituted with oxo (=0). A ring carbon atom that is connected to the nitrogen atom in -N(R16)- is not substituted with oxo. Where such a carbon ring atom is substituted with oxo it may be joined to a further nitrogen ring atom (where such is present) to from an amide group. It is noted that a further nitrogen atom may be connected to the carbon atom that is a to the group -X-. The inventors understand that where an amide group is present within a nitrogen-containing heterocycle as a substituent to the carbon β to the group -X-, biological activity is not reduced.
In one embodiment, where a ring carbon atom is connected to a further nitrogen ring atom that is connected to the carbon atom that is a to the group -X-, that ring carbon atom is not substituted with oxo. Similarly, where such a carbon ring atom is substituted with oxo it may be joined to a further oxygen ring atom (where such is present) and an ester group may be formed.
In one embodiment, the nitrogen-containing heterocycle does not include a ring amide, carbamate, urea or ester group.
In one embodiment, a further nitrogen ring atom connected to the carbon that is a to the group -X- is not part of an amide, carbamate or urea group.
In one embodiment, a further oxygen ring atom connected to the carbon that is a to the group -X- is not part of a carbamate or ester group. Where -R17 and -RA form a monocyclic nitrogen-containing heterocycle, one ring atom
(formed together with the carbon atoms a and β to the group -X-) must be substituted. Here the monocyclic nitrogen heterocycle must have a substituent group present on a carbon ring atom or further nitrogen ring atom, where present. Thus at least one group -Rc, -RN, -RNA or -LB-RBB must be present as a substituent to the nitrogen-containing heterocycle. In one embodiment, at least one group -Rc, -RN and -RNA must be present as a substituent to the nitrogen-containing heterocycle. In one embodiment, where -R17 and -RA form a monocyclic nitrogen-containing heterocycie, one or two ring atoms in -R17 and -RA are substituted. The remaining ring atoms in -R17 and -RA are unsubstituted. In one embodiment, one ring atom in -R17 and -RA is substituted. In one embodiment, where R17 and -RA form a monocyclic nitrogen-containing heterocycie, one carbon ring atom in -R1 and -RA is substituted with -Rc, and the remaining ring atom in -R17 and -RA are unsubstituted.
In one embodiment, where R17 and -RA form a monocyclic nitrogen-containing heterocycie, and the heterocycie has a further nitrogen ring atom, the further nitrogen is substituted with -RN or -RNA, as appropriate, and the remaining ring atoms in -R17 and -RA are unsubstituted. In one embodiment, where R17 and -RA form a monocyclic nitrogen-containing heterocycie, and the heterocycie has a further nitrogen ring atom, one carbon ring atom in -R17 and -RA is substituted with -Rc, and the remaining ring atoms in -R1 and -RA are unsubstituted. Where -R17 and -RB form a monocyclic nitrogen heterocycie, the ring atoms in the ring (formed together with the carbon atom β to the group -X-) need not be substituted. If the group -RA is hydrogen, the monocyclic nitrogen heterocycie must have a substituent group present on a carbon ring atom or further nitrogen ring atom, where present. However, if the group -RA is not hydrogen, then the carbon ring atoms or further nitrogen ring atom, where present, need not be substituted.
In one embodiment, where -R17 and -RB form a monocyclic nitrogen-containing heterocycie, one or two ring atoms in -R17 and -RB are substituted. The remaining ring atoms in -R1 and -RB are unsubstituted. In one embodiment, one ring atoms in -R17 and -RB is substituted. In these embodiments, -RA may be hydrogen.
In one embodiment, where R17 and -RB form a monocyclic nitrogen-containing heterocycie, one carbon ring atom in -R17 and -RB is substituted with -Rc , and the remaining ring atoms in
-R1 / and -RB are unsubstituted.
In one embodiment, where R17 and -RB form a monocyclic nitrogen-containing heterocycie, and the heterocycie has a further nitrogen ring atom, the further nitrogen is substituted with
-RN, and the remaining ring atoms in -R17 and -RB are unsubstituted.
In one embodiment, where R17 and -RB form a monocyclic nitrogen-containing heterocycie, and the heterocycie has a further nitrogen ring atom, one carbon ring atom in -R17 and -RB is substituted with -Rc , and the remaining ring atoms in -R17 and -RB are unsubstituted.
A bicyclic nitrogen-containing heterocycie may be unsubstituted. Here the second fused ring may be regarded as a substituent to the first ring.
In one embodiment, where R17 and -RA form a bicyclic nitrogen-containing heterocycie, one carbon ring atom in -R17 and -RA is substituted with -RD, and the remaining ring atoms in -R17 and -RA are unsubstituted. In one embodiment, where R17 and -RA form a bicyclic nitrogen-containing heterocycle, and the heterocycle has a further nitrogen ring atom, the further nitrogen is substituted with -RN or -RNA, as appropriate, and the remaining ring atoms in -R17 and -RA are unsubstituted. In one embodiment, where R17 and -RA form a bicyclic nitrogen-containing heterocycle, and the heterocycle has a further nitrogen ring atom, one carbon ring atom in -R17 and -RA is substituted with -RD, and the remaining ring atoms in -R17 and -RA are unsubstituted.
In one embodiment, a group -RD is -Rc when it is provided as a substituent on the first ring of a bicyclic nitrogen-containing heterocycle.
-R°
In one embodiment, each -RD is independently selected from -Rc, halo, -OH, and -NH2. In one embodiment, each -RD is independently selected from -Rc and halo.
In one embodiment, each -RD is independently -Rc.
In one embodiment, each -RD is independently -Lc-Rcc.
A bicyclic nitrogen-containing heterocycle contains a first ring and a second ring. The first ring is the nitrogen heterocycle including the carbon atom that is β to the group -X-.
In one embodiment each carbon ring atom in -R17 and -RA that is part of the first ring is optionally mono- or di-substituted with -Rc.
The second ring is the ring fused to the first ring. Each carbon ring atom in -R 7 and -RA that is part of the second ring is optionally mono- or di-substituted with -RD. -ΖΛ
The group -LA- may be a covalent bond.
Alternatively -LA- may be a linking group. An asterisk is used to indicate the point at which the group point of attachment of the group -LA- to -RAA. Thus, the remaining attachment point connects to the carbon that is a to the group -X-.
It is noted that -LA- is not a group -N(R11)C(0)-* where the asterisk is the point of attachment to -RAA. The inventors have found that such groups have a poor biological activity, as discussed above.
In one embodiment, the linking group is selected from -R1 -*, -O-L^-*, -N(R11)-LAA-*, and -0(0)-^-*.
In one embodiment, the linking group is selected from -R' -*, -O-L^-*, and -C(0)-LAA-*.
In one embodiment, the linking group is selected from -RL- *, -N(R11)-LAA-*, and -C(0)-LAA- In one embodiment, the linking group is selected from -R1 -* and -0(0)-^-*.
In one embodiment, the linking group is selected from -RL-*, -O-L^-*, and -N(R11)-LAA-*. In one embodiment, the linking group is selected from -RL-* and -0-LAA-*. In one embodiment, the linking group is -RL-*. -LB- The group -LB- may be a covalent bond.
Alternatively -LB- may be a linking group.
An asterisk is used to indicate the point at which the group point of attachment of the group -LB- to -RBB. Thus, the remaining attachment point connects to the carbon that is β to the group -X- (i.e. the carbon atom in -CH(RB)-).
In one embodiment, the linking group is selected from R1-*, -O-L^-*, -00(0)-^-*, -N(R1 1 )-LAA-*, -C(0)-LAA-*, and -0(0)0-1./ -*.
In one embodiment, the linking group is selected from -R1 -*, -O-L^-*, -N(R1 1 )-LAA-*,
-0(0)-!.^-*, -C(0)0-LAA-*, and -C(0)N(R11)-LAA-*.
In one embodiment, the linking group is selected from -R1 -*, -0-LAA-*, -N(R1 1 )-LAA-*,
-0(0)-^-*, and -0(0)0-^-*.
In one embodiment, the linking group is selected from -RL-*, -O-L^-*, and -N(R11)-LAA-*. In one embodiment, the linking group is -R1 -*. Additionally or alternatively, the linking group is selected from -N(R11)S(0)-LAA-* and -N(R1 1 )S(0)2-LAA-*.
In one embodiment, the linking group is -N(R1 1 )S(0)2-LAA-*.
In one embodiment, the linking group is -N(R11 )S(0)2-*. Additionally or alternatively, the linking group is selected from -S(0)N(R1 1 )-LAA-*, and
-S(0)2N(R 1)-LAA-*.
In one embodiment, the linking group is -S(0)N(R, 1 )-LAA-*.
In one embodiment, the linking group is -S(0)2N(R11 )-LAA-*. -Lc-
The group -Lc- may be a covalent bond.
Alternatively -Lc- may be a linking group.
An asterisk is used to indicate the point at which the group point of attachment of the group -Lc- to -Rcc. Thus, the remaining attachment point connects to the carbon ring atom.
In one embodiment, the linking group is selected from R1 -*, -O-L^-*, -OC(0)-LAA-*,-N(R1 1)-
LAA-*, -C(0)-LAA-*, and -C(0)0-LAA-*.
In one embodiment, the linking group is selected from -R' -*, -O-L**-*, -N(R1 1 )-LAA-*, -C(0)-LM-*, -C(0)0-LAA-*, and -C(0)N(R11)-LAA-*.
In one embodiment, the linking group is selected from -R1-*, -O-L^-*, -N(R1 1 )-LAA-*,
-0{0)-1Μ-*, and -0(0)0-^-*. In one embodiment, the linking group is selected from -RL-*, -O-L^-*, and -N(R11)-LAA-*. In one embodiment, the linking group is -R1 -*.
Additionally or alternatively, the linking group is selected from -N(R11)S(0)-LAA-* and -N(R11)S(0)2-LAA-*.
In one embodiment, the linking group is -N(R11)S(0)2-LAA-*.
In one embodiment, the linking group is -N(R11)S(0)2-*.
Additionally or alternatively, the linking group is selected from -S(0)N(R11)-LAA-*, and -S(0)2N(R11)-LAA-*.
In one embodiment, the linking group is -S(0)N(R11)-LAA-*.
In one embodiment, the linking group is -S(0)2N(R11)-LAA-*.
-LM-
In one embodiment, a group -LAA- is independently a covalent bond.
In one embodiment, a group -LAA- is independently -RL.
-LN-
In one embodiment, a group -LN- is independently a covalent bond.
In one embodiment, a group -LN- is a linking group.
An asterisk is used to indicate the point of attachment of the group -LN- to -RNN. Thus, the remaining attachment point connects to the nitrogen ring atom.
The linking group may be independently selected from -S(0)-LAA-*, -S^^-L^-*, -0(0)-^-* and -C(0)N(R, 1)-LAA-*. Thus, the linking groups may together with the nitrogen atom to which they are attached, form sulfinamide, sulfonamide, amide and urea functionality respectively.
In one embodiment, the linking group is independently selected from -S(0)2-LAA-*,
-0{0)-1Μ-* and -C(0)N(R11)-LAA-*.
In one embodiment, linking is independently selected from -S(0)2-LAA-* and
-C(0)N(R 1)-LAA-*. It is noted that the group -LN- is present only as a substituent to a further ring nitrogen atom that is not connected to the carbon that is a to the group -X-. Where a further ring nitrogen atom is connected to the carbon that is a to the group -X-, it is optionally substituted with -RL-RNN. The group -R' -RNN does not allow for sulfinamide, sulfonamide, amide and urea groups connected to the carbon that is a to the group -X-. The presence of sulfinamide, sulfonamide, amide and urea functionality is believed to be tolerated at other ring positions. -RL-
In one embodiment, each -RL- is independently selected from C1-12 alkylene, C2-12 heteroalkyiene, C3-10 cycloalkylene and C5-10 heterocyclylene.
However, where -L^- is connected to a group C1-12 alkyl, -R' - is not C1-12 alkylene. In a further embodiment, where -L^- is connected to a group C1-12 alkyl, -RL- is not C1-12 alkylene and it is not C2-12 heteroaikylene.
Where -RL- is a heteroalkyiene it may be connected to -RAA, -RBB, -Rcc, or -RNN via a heteroatom of the heteroalkyiene group, such as N, O or S, where present, or a carbon atom of the heteroalkyiene group. The other point of connection is made via a carbon atom of the heteroalkyiene group, for example where the heteroaikylene is attached to a carbon atom or a heteroatom, such as N, O or S. The other point of connection may be made via a heteroatom of the heteroaikylene group, for example where the heteroalkyiene is attached to a carbon atom. However, it is preferred that the other point of connection is made via a carbon atom of the heteroaikylene group, particularly where -RL- is present in a group -LAA-.
Where -R' - is a heterocyclylene it may be connected to -RM, -RBB, -Rcc, or -RNN via a ring nitrogen heteroatom of the heterocyclylene group, where present, or a carbon ring atom of the heterocyclylene group. The other point of connection is made via a ring carbon atom of the heterocyclylene group, for example where the heterocyclylene is attached to a carbon atom or a heteroatom, such as N, O or S. The other point of connection may be made via a ring nitrogen heteroatom of the heterocyclylene group, for example where the
heterocyclylene is attached to a carbon atom.
In one embodiment, a group -RL- is independently selected from C1 -12 alkylene, and C2-12 heteroalkyiene.
In one embodiment, a group -R1 - is independently selected from C1-12 alkylene and
C3-10 cycloalkylene.
In one embodiment, a group -R1 - is independently C1-12 alkylene.
The group -RL- may be substituted with one or more groups -Rs. Thus, each C1-12 alkylene, C2-12 heteroaikylene, C3-10 cycloalkylene and C5-10 heterocyclylene is optionally substituted with one or more groups -Rs. The specified groups may be unsubstituted or mono- substituted. The group -Rs may be present as a substituent to a carbon atom. A carbon atom may be optionally mono- or di-substituted with -Rs.
Where a nitrogen atom is present in a group, such as in a heterocyclylene group or a heteroaikylene group, that nitrogen atom may be optionally substituted with a group -R12. In one embodiment, a group -RL- is unsubstituted. In one embodiment, a C1-12 alkylene group is selected from C1-6 alkylene, C1-4 alkylene,
C2-6 alkylene, and C2-4 alkylene.
In one embodiment, an alkylene group is linear.
In one embodiment, a C1-12 alkylene group is selected from -CH2-, -CH2CH2-, and -CH(CH3)-. In one embodiment, a C1-12 alkylene group is -CH2-. for example when it is connected to a cycloalkyl, heterocyclyl, or aryl group.
In one embodiment, a C2-12 heteroalkylene group is selected from C2-6 heteroalkylene, and C2-4 heteroalklyene.
In one embodiment, a C2-12 heteroalkylene group is selected from -CH2O-*, -CH2CH2O-*, -CH2NH-*, -CH2CH2NH-*, -CH2N(R12)-*, and -CH2CH2N(R12)-*, where the asterisk indicates the point of attachment to -RM, -RBB, -Rcc, or -RNN. Thus, a heteroatom in the
heteroalkylene group may be connected to -RAA, -RBR, -Rcc, or -RNN. The other point of connection may be made via a carbon atom of the heteroalkylene group.
Where an S atom is present in the heteroalkylene group, it may be in the form S, S(O) or S(0)2.
In one embodiment, the C3-10 cycloaikylene is selected from cyciopropylene, cyclopentylene and cyclohexylene. In one embodiment, the C3-10 cycloaikylene is cyclohexylene.
In one embodiment, the C5-10 heterocyclylene is C 6 heterocyclylene.
In one embodiment, the C5-10 heterocyclylene is selected from piperidinene, piperazinene, morpholinene and thiomorphoiinene. The heterocyclylene may be connected to -RM, -RBB, -Rcc, or -RNN via a ring carbon or ring nitrogen atom. The other point of connection may be made via a carbon atom of the heterocyclylene group.
A nitrogen atom, where present, is optionally substituted with -R12.
Where an S atom is present in the heterocyclylene group, it may be in the form S, S(O) or
S(0)2. -RAA, -RBB, -Rcc, and -RNN
Each of -RAA, -RBB, -Rcc, and -RNN, where present, is independently selected from C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, and C5-12 aryl. In one embodiment, a C1-12 alkyl group is selected from Ci-r, alkyl, C1-7 alkyl, C1-4 alkyl, C2-6 alkyl, C2-1 alkyl, C3-10 alkyl, C3-7 alkyl, C4-10 alkyl and Ce-io alkyl.
In one embodiment, an alkyl group is linear.
In one embodiment, an alkyl group is branched. In one embodiment, the C1-12 alkyl group does not include Ce alkyl.
In one embodiment, a C3-10 cycloalkyl group is C3-6 cycloalkyl or C5-6 cycloalkyl. In one embodiment, a C3-10 cycloalkyl group is cyclohexyl.
In one embodiment, a C4-10 heterocyciyi group is selected from C5-10 heterocyciyi,
Ce-10 heterocyciyi, C5-7 heterocyciyi and C5-6 heterocyciyi.
In one embodiment, a C4-10 heterocyciyi group is selected from tetrahydrofuranyl, pyrrolidinyl, tetrahydropyranyl, morpholinyl, thiomorpholinyl, piperidinyl and piperazinyl.
In one embodiment, a C4-10 heterocyciyi group is selected from tetrahydropyanyl,
morpholinyl, piperidinyl and piperazinyl.
Where an S atom is present in a heterocyciyi group, it may be in the form S, S(O) or S(0)2. A nitrogen atom, where present, is optionally substituted with -R12.
A heterocyciyi group may be connected via a ring nitrogen heteroatom atom or a ring carbon atom. Where the heterocyciyi group is a substituent to a nitrogen atom (e.g. present in the group -RL-), the heterocyciyi group is connected to that nitrogen atom via a ring carbon atom.
An aryl group, particularly a heteroaryl group such as indole, may be connected via a ring nitrogen heteroatom atom or a ring carbon atom. Where the heteroaryl group is a
substituent to a nitrogen atom, the heteroaryl group is connected to that nitrogen atom via a ring carbon atom. Typically, the aryl group is connected via a ring carbon atom.
In one embodiment, the C5-12 aryl is selected from Ce-12 carboaryl and C5-12 heteroaryl.
In one embodiment, the C5-12 aryl is selected from phenyl, pyridyl, and naphthyl, optionally together with 1 ,3-benzodioxolyl and pyridonyl. In one embodiment, the Cr>-12 carboaryl is selected from phenyl, naphthyl, chromanyl, iso- chromanyl and 1 ,3-benzodioxolyl. The chromanyl, iso-chromanyl and 1 ,3-benzodioxolyl groups are connected via an aromatic ring carbon atom. Further discussion about the meaning of the term carboaryl is provided below with reference to the group -G.
In one embodiment, the Ce-12 carboaryl is selected from phenyl and naphthyl,
In one embodiment, the C5-12 heteroaryl is selected from C5-10 heteroaryl and C5-6 heteroaryl. In one embodiment, the C5-12 heteroaryl is selected from the group consisting of
independently furanyl, thienyl, pyrrolyl, imidazoly!, pyrazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, quinolinyl, isoquinolinyl, indolyl and pyridonyl.
Further discussion about the meaning of the term heteroaryl is provided below with reference to the group -G.
Each C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyciyi, and C5-12 aryl group is optionally substituted with -Rs at carbon and -R12 at nitrogen, where present. Each group may have one, two, three or more groups -Rs. In one embodiment, a heterocyciyi group or a heteroaryl group may have one, two, three or more groups -R12. In one embodiment, a group is mono-subsituted.
In one embodiment, a group is unsubstituted.
The group -Rs is present as a substituent to a carbon atom. A carbon atom may be optionally mono- or di-substituted with -Rs.
Where a nitrogen atom is provided, such as in a heterocyclyl group or a heteroaryl group, that nitrogen may be optionally substituted with a group -R12.
In one embodiment, - M is independently selected from C1-12 a Iky I and C5-12 aryl.
In one embodiment, -RM is independently C1-12 alkyl. In one embodiment, -RAA is independently C2-12 alkyl, such as C3-12 alkyl.
In one embodiment, -RM is independently C5-12 aryl.
In one embodiment, -RBB is independently selected from C1-12 alkyl, C4-10 heterocyclyl, and C5-12 aryl, for example when -LB- is a covalent bond, or for example when -RA is hydrogen. In one embodiment, -RBB is independently selected from C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, and C5-12 aryl, for example when -RB is a substituent to a heterocycle ring carbon atom.
In one embodiment, -RBB is independently selected from C1-12 alkyl and C5-12 aryl.
In one embodiment, -RBB is independently C1-12 alkyl. In one embodiment, -RBB is independently C2-12 alkyl, such as C3-12 alkyl.
In one embodiment, -RBB is independently C5-12 aryl.
In one embodiment, a group -RNN is independently selected from C1-12 alkyl and C5-12 aryl. In one embodiment, -RNN is independently C1-12 alkyl. In one embodiment, -RNN is independently C2-12 alkyl, such as C3-12 alkyl.
In one embodiment, -RNN is independently C5-12 aryl.
-Rs
The group -Rs is an optional substituent to each C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, C5-12 aryl, C1-12 alkylene, C2-12 heteroalkylene, C3-10 cycloalkylene and C5-10 heterocyclylene group. Where a group is optionally substituted, it may be optionally substituted with one or more groups -Rs. A group may be optionally mono-substituted with -Rs.
The group -Rs is an optional substituent to a carbon atom. A carbon atom may be mono-, di- or tri-substituted. In one embodiment, each -Rs, where present, is independently selected from -OH, -OR12, halo, -R12, -NHR12, -NR12R13, -C(0)R12, -COOH and -COOR12. In one embodiment, each -Rs, where present, is independently selected from -OR12, halo, -R12, -NHR12, -NR12R13, -C(0)R12, -COOH and -COOR12.
In one embodiment, each -Rs, where present, is independently selected from -OR12, halo, and -R12.
Where -Rs is a substituent to an a Iky I group, -Rs is not -R12.
Where -Rs is halo it may be selected from fluoro, chloro, bromo and iodo, such as chloro and bromo, such as chloro. In one embodiment, where a carbon atom is di-substituted with -Rs, these groups may together with the carbon to which they are attached form a C3-6 carbocycle or a C»-e heterocycle, where the carbocycle and the heterocycle are optionally substituted with one or more groups -R 2. Where an S atom is present in the heterocycle group, it may be in the form S, S(O) or S(0)2.
In one embodiment, a C3-6 carbocycle is cyclopentane or cyclohexane, such as cyclohexane. In one embodiment, a C5-6 heterocycle is selected from piperidine, piperazine, morpholine, thiomorpholine, tetrahydrofuran and tetrahyd ropy ran.
-R12 and -R13
Each -R12 and -R13 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl.
Where -R12 and -R13 are both attached to N, they may together with the N atom form a 5- or 6-membered heterocycle, such as pyrrolidine, piperazine, piperidine, thiomorpholine or morpholine. The heterocyclic ring is optionally substituted with C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl.
In one embodiment, a -R12 or -R13 group is independently C1-6 alkyl, phenyl or benzyl.
In one embodiment, a -R12 or -R13 group is independently C1-6 alkyl. In one embodiment, the C1-6 alkyl is selected from methyl and ethyl.
In one embodiment, the C1-6 haloalkyl is -CF3.
-R11 In one embodiment, a group -R11 is independently selected from hydrogen, methyl and ethyl. In one embodiment, -R11 is independently hydrogen.
-R1
The -R1 position corresponds to amino acid position 6 in the polymyxin compounds. In one embodiment -R1 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a phenylalanine residue, for example a D-phenylalanine, or a leucine residue, such as a D-leucine residue. -R2
The -R2 position corresponds to amino acid position 7 in the polymyxin compounds.
In one embodiment -R2 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a leucine or threonine residue, such as L-leucine or L-threonine.
-R3
The -R3 position corresponds to amino acid position 10 in the polymyxin compounds.
In one embodiment -R3 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a threonine residue, such as L-threonine.
-R4
The -R4 position corresponds to the side chain of the amino acid position 3 in the polymyxin compounds.
The group -R4 together the carbonyl group and nitrogen alpha to the carbon to which it is attached, is an amino acid residue having an amino- or hydroxyl-containing side chain. In one embodiment, -R4 is Ci_i alkyl, having one amino or one hydroxyl substituent.
In one embodiment, -R4 has one amino substituent.
In one embodiment, -R4 has one hydroxyl substituent.
The amino group may be -Nh , -NHMe or -NHEt. In one embodiment, the amino group is
-NH2.
In one embodiment, -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is α,γ-diaminobutyric acid (Dab), a serine residue, a threonine residue, a lysine residue, an ornithine residue, or α.β-diaminopropionic acid (Dap).
In one embodiment, -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is γ-diaminobutyric acid (Dab), a serine residue, a lysine residue, or α.β-diaminopropionic acid (Dap).
In one embodiment, -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is α.γ-diaminobutyric acid (Dab) or a. β-diaminopropionic acid (Dap), such as L-Dab or L-Dap. In one embodiment, -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is α,γ-diaminobutyric acid (Dab) or a, β-diaminopropionic acid (Dap), such as L-Dab or L-Dap.
In one embodiment, -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is a lysine residue, such as L-Lys.
In one embodiment, -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is Dab, such as L-Dab.
Compounds of the invention where -R4 is a Dab side chain are obtainable from compounds such as Polymyxin B. Compounds where -R4 is a Dap side chain may be prepared using the methods described in WO 2012/168820. Compounds where -R4 is a serine side chain may be prepared using the methods described by Vaara et al. (see, for example, Antimicrob. Agents Chemother. 2008, 52, 3229). -R8
The amino acid residue including the group -R8 corresponds to position 2 in the polymyxins. In one embodiment, -R8 is methyl. The resulting amino acid is therefore Thr.
In one embodiment, -R8 is H. The resulting amino acid is therefore Ser.
-X-
The group -X- may be selected from -NHC(O)-, -C(O)-, -OC(O)-, -CH2- and -SO2-.
In one embodiment -X- is selected from -C(O)-, -SO2- and -CH2-.
In one embodiment -X- is -C(O)-.
In one embodiment -X- is -SO2-.
In one embodiment -X- is -CH2-.
The right-hand side of the group -X- is the point of attachment to NH, the amino terminal of the amino acid at position 2. The left-hand side of the group -X- is the point of attachment to -R5 or -R15.
Heterocyclyl, Cycloalkyl, and Aryl
For the avoidance of doubt, the index "Cx.y" in terms such as "C4-7 heterocyclyl", and the like, refers to the number of ring atoms, which may be carbon atoms or heteroatoms (e.g., N, O, S). For example, piperidinyl is an example of a Ceheterocycyl group.
The term "heterocyclyl" in reference to the group -D refers to a group (1 ) which has one or more heteroatoms (e.g., N, O, S) forming part of a ring system, wherein the ring system comprises one ring or two or more fused rings, wherein at least one ring of the ring system is a non-aromatic ring, and (2) which is attached to the rest of the molecule by a non-aromatic ring atom (i.e., a ring atom that is part of a non-aromatic ring that is part of the ring system). For example: piperidino and piperidin-4-yl are both examples of a Ceheterocycyl group; 2,3-dihydro-1 H-indol-1-yl is an example of a Cgheterocycyl group; and both decahydro- quinolin-5-yl and 1.2,3.4-tetrahydro uinolin-4-yl are examples of a Cioheterocyclyl group.
Figure imgf000046_0001
-4-yl
Figure imgf000046_0002
2,3-dihydro-1 H-indol-1-yl decahydro-quinolin-5-yl 1 ,2,3,4-tetrahydro-quinolin-4-yl
In one embodiment, where a heterocyclyl group contains two or more fused rings, each ring is non-aromatic.
In one embodiment, the heterocyclyl group comprises one ring.
For the avoidance of doubt, "cycloalkyl" refers to a group (1 ) which has a ring system comprising one ring or two or more fused rings, wherein one ring of the fused ring system may be an aromatic ring, and (2) which is attached to the rest of the molecule by a non-aromatic ring atom (i.e., a ring atom that is part of a non-aromatic ring that is part of the ring system). For example: cycloalkyl is an example of a Ce cycloalkyl group; and
tetralin-2-yl is an example of a Cio cycloalkyl group.
Figure imgf000046_0003
cyclohexyi tetralin-2-yl
Where an aromatic ring is present, it may be optionally substituted. In one embodiment, where the cycloalkyl comprises two or more fused rings, each ring is non-aromatic.
In one embodiment, the cycloalkyl group comprises one ring.
For the avoidance of doubt, "heteroaryl" refers to a group (1 ) which has one or more heteroatoms (e.g., N, O, S) forming part of a ring system, wherein the ring system comprises one ring or two or more fused rings, wherein at least one ring of the ring system is an aromatic ring, and (2) which is attached to the rest of the molecule by an aromatic ring atom (i.e., a ring atom that is part of an aromatic ring that is part of the ring system). For example: pyridyl is an example of a Ccheteroaryl group; isoquinolyl is an example of a Cioheteroaryl group; and 1 ,2.3,4-tetrahydro-isoquinoline-7-yl is an example of a Cioheteroaryl group.
Figure imgf000047_0001
pyrid-3-yl isoquinolin-7-yl 1.2,3,4-tetrahydro-isoquinolin-7-yl
In one embodiment, where a heteroaryl comprises two or more fused rings, each ring is an aromatic ring.
In one embodiment, the heteroaryl group comprises one aromatic ring.
A heteroaryl group may also include a pyridonyl group, which may be regarded as a structure corresponding to a pyridinyl group having a 2- or 4- hydroxyl substituent.
In one embodiment, a heteroaryl group is not a pyridonyl group.
Similarly, "carboaryl" refers to a group (1 ) which has a ring system comprising one ring or two or more fused rings, wherein at least one ring of the ring system is an aromatic ring, and (2) which is attached to the rest of the molecule by an aromatic ring atom (i.e., a ring atom that is part of an aromatic ring that is part of the ring system). For example: phenyl is an example of a Ce carboaryl group; and tetralin-6-yl is an example of a Cio carboaryl group.
Figure imgf000047_0002
phenyl tetralin-6-yl
In one embodiment, where a carboaryl comprises two or more fused rings, each ring is an aromatic ring.
Where a non-aromatic ring is present, that ring may be a carbocycle (such as shown above for tetralin), or the ring may be a heterocycle, as shown below for the group
dihydrobenzo[b][1.4]dioxin-6-yl.
Figure imgf000047_0003
dihydrobenzo[b][1 ,4]dioxin-6-yl
Salts, Solvates and Other Forms
Examples of salts of compound of formula (III) include all pharmaceutically acceptable salts, such as, without limitation, acid addition salts of strong mineral acids such as HCI and HBr salts and addition salts of strong organic acids such as a methanesulfonic acid salt. Further examples of salts include sulphates and acetates such as trifluoroacetate or trichloroacetate.
In one embodiment, the salt is an acetate salt.
In one embodiment the compounds of the present disclosure are provided as a sulphate salt or a trifluoroacetic acid (TFA) salt. In one embodiment the compounds of the present disclosure are provided as acetate salts. A compound of formula (III) can also be formulated as prodrug. Prodrugs can include an antibacterial compound herein described in which one or more amino groups are protected with a group which can be cleaved in vivo, to liberate the biologically active compound. In one embodiment the prodrug is an ' amine prodrug". Examples of amine prodrugs include sulphomethyl, as described in e.g., Bergen et al, Antimicrob. Agents and Chemotherapy, 2006, 50, 1953 or HS03-FMOC, as described in e.g. Schechter et al, J.Med Chem 2002, 45(19) 4264, and salts thereof. Further examples of amine prodrugs are given by Krise and Oliyai in Biotechnology: Pharmaceutical Aspects, 2007, 5(2), 101 -131.
In one embodiment a compound of formula (III) is provided as a prodrug.
A reference to a compound of formula (III) is also a reference to a solvate of that compound. Examples of solvates include hydrates.
A compound of formula (III) includes a compound where an atom is replaced by a naturally occurring or non-naturally occurring isotope. In one embodiment the isotope is a stable isotope. Thus a compound described here includes, for example deuterium containing compounds and the like. For example, H may be in any isotopic form, including 1H, 2H (D), and 3H (T); C may be in any isotopic form, including 12C, 13C, and 14C; O may be in any isotopic form, including 160 and 180; and the like.
Certain compounds of formula (III) may exist in one or more particular geometric, optical, enantiomeric, diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r- forms; endo- and exo-forms; R-, S-, and meso-forms; D- and L-forms; d- and l-forms; (+) and (-) forms; keto-, enol-, and enolate-forms; syn- and anti-forms; synclinal- and anticlinal-forms; a- and β-forms; axial and equatorial forms; boat-, chair-, twist-, envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as
"isomers" (or "isomeric forms"). Note that, except as discussed below for tautomeric forms, specifically excluded from the term "isomers," as used herein, are structural (or constitutional) isomers (i.e., isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, -OCH3, is not to be construed as a reference to its structural isomer, a hydroxymethyl group, -CH2OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its structural isomer, meta- chlorophenyl. However, a reference to a class of structures may well include structurally isomeric forms falling within that class (e.g., Ci-ealkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and para- methoxyphenyl).
Unless otherwise specified, a reference to a particular compound includes all such isomeric forms, including mixtures (e.g., racemic mixtures) thereof. Methods for the preparation (e.g., asymmetric synthesis) and separation (e.g., fractional crystallisation and
chromatographic means) of such isomeric forms are either known in the art or are readily obtained by adapting the methods taught herein, or known methods, in a known manner. It is noted that certain substituent groups in the compounds of formula (I I I), such as R15, are given with specific stereochemical configurations.
One aspect of the present invention pertains to compounds in substantially purified form and/or in a form substantially free from contaminants.
In one embodiment, the substantially purified form is at least 50% by weight, e.g., at least 60% by weight, e.g., at least 70% by weight, e.g., at least 80% by weight, e.g., at least 90% by weight, e.g., at least 95% by weight, e.g., at least 97% by weight, e.g., at least 98% by weight, e.g., at least 99% by weight.
Unless specified, the substantially purified form refers to the compound in any
stereoisomeric or enantiomeric form. For example, in one embodiment, the substantially purified form refers to a mixture of stereoisomers, i.e., purified with respect to other compounds. In one embodiment, the substantially purified form refers to one stereoisomer, e.g., optically pure stereoisomer. In one embodiment, the substantially purified form refers to a mixture of enantiomers. In one embodiment, the substantially purified form refers to an equimolar mixture of enantiomers (i.e., a racemic mixture, a racemate). In one embodiment, the substantially purified form refers to one enantiomer, e.g., optically pure enantiomer. In one embodiment, the contaminants represent no more than 50% by weight, e.g., no more than 40% by weight, e.g., no more than 30% by weight, e.g., no more than 20% by weight, e.g., no more than 10% by weight, e.g., no more than 5% by weight, e.g., no more than 3% by weight, e.g., no more than 2% by weight, e.g., no more than 1 % by weight. Unless specified, the contaminants refer to other compounds, that is, other than
stereoisomers or enantiomers. In one embodiment, the contaminants refer to other compounds and other stereoisomers. In one embodiment, the contaminants refer to other compounds and the other enantiomer.
In one embodiment, the substantially purified form is at least 60% optically pure (i.e., 60% of the compound, on a molar basis, is the desired stereoisomer or enantiomer, and 40% is the undesired stereoisomer or enantiomer), e.g., at least 70% optically pure, e.g., at least 80% optically pure, e.g., at least 90% optically pure, e.g., at least 95% optically pure, e.g., at least 97% optically pure, e.g., at least 98% optically pure, e.g., at least 99% optically pure. The compounds of the invention also include the chemically protected forms thereof. For example amino functionality within the compound may be protected as the ferf-butoxy (-Boc) form. As a further example, hydroxy I functionality within the compound may be protected as the iert-butyl (f-Bu) form. Protected froms are discussed in detail in the section below. Protected Forms
Compounds of formula (III) may be provided in a protected form. Here, reactive
functionality, such as amino functionality, may be masked in order to prevent its reaction during a synthesis step. A protecting group is provided to mask the reactive functionality, and this protecting groups may be removed at a later stage of the synthesis to reveal the original reactive functionality.
A compound of formula (Ilia) is provided, and salts, solvates and hydrates thereof, which is a compound of formula (III) in protected form. For example, amino, hydroxyl, carboxyl and thiol functionality present in compound (III) may be protected with a protecting group, such as described herein. The compound of formula (Ilia) may be an intermediate for the preparation of the compound of formula (III). Thus, compound (III) may be prepared from compound (Ilia), for example by removal of the protecting groups ("deprotection"). In one embodiment, the protected form is a compound where amino, hydroxyl, thiol, and/or carboxyl functionality is protected (masked) by a protecting group. In one embodiment, the protected form is a compound where the side chain functionality of the amino acids residues with the compound are protected. In the compound of formula (III), the amino acid residues at positions 5, 8 and 9 are Dab residues, and the side chain of the Dab residue includes amino functionality. The amino acid functionality of each Dab residue may be protected with an amino protecting group, as described herein. In certain embodiments of the invention, -R3 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is an amino acid residue where the side chain includes hydroxyl functionality. An example of an amino acid residue including -R3 is threonine. The hydroxyl functionality of this residue may be protected with a hydroxy I protecting group, as described herein.
The group -R8 is part of an amino acid residue where the side chain includes hydroxyl functionality. The amino acid residue including group -R8 may be serine or threonine. The hydroxyl functionality of these residues may be protected with a hydroxyl protecting group, as described herein.
The group -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is an amino acid residue where the side chain includes hydroxyl functionality or amino functionality. An example of an amino acid residue including -R4 is Dab. The hydroxyl or amino functionality of these residues may be protected with a hydroxyl or amino protecting group, as described herein. In certain embodiments the group -R15 contains functionality such as amino, hydroxyl carboxyl or thiol functionality. The amino, hydroxyl carboxyl or thiol functionality may be protected with amino, hydroxyl carboxyl or thiol protecting groups, as described herein.
Protecting groups, such as those for amino acid residues, are well known and well described in the art.
Amino acids having side group protection, optionally together with amino and carboxy protection, are commercially available. Thus, a protected polymyxin compound may be prepared from appropriately protected amino acid starting materials.
Velkov et al. describe the step-wise preparation of polymyxin compounds on the solid-phase using suitably protected amino acids. The use of protected-forms of threonine and Dab is disclosed (see Supplementary Information). Velkov et al. do not describe compounds of formula (III), for at least the reason that the group -R15 is not described or exemplified in Velkov et al.
Where a protecting group is used is it is removable under conditions that do not substantially disrupt the structure of the polymyxin core, for example conditions that do not alter the stereochemistry of the amino acid residues.
In one embodiment, the protecting groups are acid-labile, base labile, or are removable under reducing conditions. Example protecting groups for amino functionality include Boc (tert-butoxycabonyl), Bn
(benzyl, Bzl), CbZ (Z), 2-CL-Z (2-chloro), Dde (1 -[4,4-dimethyl-2,6-dioxocylcohex-1-ylidene]- 3-methylbutyl), Fmoc (fluorenylmethyloxycarbonyl), HSOa-Fmoc (suifonylated Fmoc, such as 2-sulfo-Fmoc, as described in e.g. Schechter et al, J.Med Chem 2002, 45(19) 4264), ivDde (1 -[4,4-dimethyl-2,6-dioxocylcohex-1-ylidene]ethyl), Mmt (4-methoxytrityl), Mtt
(4-methyltrityl), Nvoc (6-nitroveratroyloxycarbonyi), and Tfa (trifluroacetyl). Example protecting groups for aromatic nitrogen functionality includes Boc, Mtt, Trt and Dnp (dinitrophenyl).
In one embodiment, the protecting group for amino functionality is selected from Boc, CbZ, Bn and Fmoc and HSCVFmoc.
In one embodiment, the protecting group for amino functionality is Boc, Fmoc or CbZ.
Example protecting groups for hydroxy I functionality include Trt (trityl), Bn (benzyl), tBu (terf-butyl), and 2-acetamido-2-deoxy-3.4,6-tri-Oacetyl-a-galactopyranosyl.
In one embodiment, the protecting group for hydroxyl functionality is Trt.
Further example protecting groups for hydroxyl functionality include silyl ether protecting groups, such as TMS, TES, TBS, TIPS, TBDMS, and TBDPS. Such protecting groups are removable with TBAF, for example. Example protecting groups for carboxyl functionality include Bn (benzyl, Bz), tBu (tert-butyl), TMSET (trimethylsilylethyl) and Dmab ({1-[4,4-dimethyl-2.6-dioxocylcohex-1 -ylidene]-3- methylbutyljamino benzyl).
In some embodiments, only some types of functionality are protected. For example, only amino groups may be protected, such as amino groups in the side chain of an amino acid residue.
In one embodiment, amino groups and hydroxyl groups are protected. Active Agent
The compounds of formula (III) may each be used together with a second agent. The inventors have found that such combinations have greater biological activity than would be expected from the individual activity of both compounds. The compounds of formula (III) can be used to potentiate the activity of the second agent. In particular, the compounds of formula (III) may be used together with a second agent to enhance the antimicrobial activity of that agent, for example against Gram-negative bacteria.
Without wishing to be bound by theory it is believed that the compounds of formula (III) act on the outer membrane of a cell e.g. a Gram-negative bacterial cell, to facilitate the uptake of the second agent into that cell. Thus, agents that are otherwise incapable or poor at crossing the outer membrane may be taken up into a target cell by the action of the compounds of formula (III).
In one embodiment, the combination of a compound of formula (III) with the second agent is active against Gram-negative bacteria. Here, it is not essential that individually either of the compound of formula (III) or the second agent have activity against Gram-negative bacteria.
In one embodiment, the second agent is an agent having a measured MIC value against a particular microorganism, such as a bacterium, that is less than 10, less than 5, or less than 1 micrograms/mL. The microorganism may be a Gram-negative bacteria, such as a Gram- negative bacteria selected from the group consisting of E. coli, S. enterica, K. pneumoniae, K. oxytoca; E. cloacae. E. aerogenes, E. agglomerans, A. caicoaceticus, A. baumannii; Pseudomonas aeruginosa, Stenotrophomonas maltophila, Providencia stuartii, P. mirabilis, and P. vulgaris.
Examples of second agents that have activity against Gram-negative bacteria include beta-lactams, tetracyclines, aminoglycosides and quinolones.
In one embodiment, the second agent is an agent having a measured MIC value against a particular microorganism, such as a Gram-negative bacterium, that is more than 4, more than 8, more than 16 or more than 32 micrograms/mL. In this embodiment, the second agent may be active against Gram-positive bacteria. For example, the second agent is an agent having a measured MIC value against a particular Gram-positive bacterium that is less than 10, less than 5, or less than 1 micrograms/mL. Here, the compound of formula (III) acts to facilitate the uptake of the second agent into the Gram-negative bacterial cell. The second agent is therefore able to act on a target within the Gram-negative bacterial cell, which target may be the same as the second agent's target in a Gram-positive bacterial cell.
The Gram-positive bacteria may be selected from the group consisting of Staphylococcus and Streptococcus bacteria, such as S. aureus (including MRSA), S. epidermis, E. faecalis, and E. faecium.
Examples of second agents that have activity against Gram-positive bacteria (at the MIC values given above, for example), and moderate activity against Gram-negative bacteria, include rifampicin, novobiocin, macrolides, pleuromutilins. In one embodiment, a compound having moderate activity against Gram-negative bacteria may have a measured MIC value against a Gram-negative bacterium that is less than 32, less than 64, or less than 128 micrograms/mL. Also suitable for use are agents having activity against Gram-positive bacteria and which are essentially inactive against Gram-negative bacteria. Examples include fusidic acid, oxazolidinines (e.g. linezolid), glycopeptides (e.g. vancomycin), daptomycin and lantibiotics. In one embodiment, a compound having essentially no activity against Gram-negative bacteria may have a measured MIC value against a Gram-negative bacterium that is more than 32, more then 64, more than 128, more than 256 micrograms/mL. Under normal circumstances such agents are not necessarily suitable for use against Gram- negative bacteria owing to their relatively poor ability to cross the outer membrane of a Gram-negative bacterial cell. As explained above, when used together with a compound of formula (III), such agents are suitable for use. In one embodiment, the active agent may be selected from the group consisting of rifampicin (rifampin), rifabutin, rifalazil, rifapentine, rifaximin, aztreonam, oxacillin, novobiocin, fusidic acid, azithromycin, ciprofloxacin, meropenem, tigecycline, erythromycin, clarithromycin and mupirocin, and pharmaceutically acceptable salts, solvates and prodrug forms thereof. The present inventors have found that the polymyxin compounds of formula (III) may be used together with certain compounds in the rifamycin family to treat microbial infections. The rifamycin family includes isolates rifamycin A, B, C, D, E, S and SV, and synthetically derivatised versions of these compounds, such as rifampicin (rifampin), rifabutin, rifalazil, rifapentine, and rifaximin, and pharmaceutically acceptable salts and solvates thereof.
In one embodiment, the active agent is rifampicin (rifampin) and pharmaceutically acceptable salts, solvates and prodrug forms thereof.
Methods of Treatment The compounds of formula (III), or pharmaceutical formulations containing these
compounds, are suitable for use in methods of treatment and prophylaxis. The compounds may be administered to a subject in need thereof. The compounds are suitable for use together with an active agent ("a second active agent"), for example a second active agent that is an antimicrobial agent.
The compounds of formula (III) are for use in a method of treatment of the human or animal body by therapy. In some aspects of the invention, a compound of formula (III) may be administered to a mammalian subject, such as a human, in order to treat a microbial infection.
Another aspect of the present invention pertains to use of a compound of formula (III) in the manufacture of a medicament for use in treatment. In one embodiment, the medicament comprises a compound of formula (III). In one embodiment, the medicament is for use in the treatment of a microbial infection.
The term "microbial infection" refers to the invasion of the host animal by pathogenic microbes. This includes the excessive growth of microbes that are normally present in or on the body of an animal. More generally, a microbial infection can be any situation in which the presence of a microbial population(s) is damaging to a host animal. Thus, an animal is "suffering" from a microbial infection when excessive numbers of a microbial population are present in or on an animal's body, or when the presence of a microbial population(s) is damaging the cells or other tissue of an animal.
The compounds may be used to treat a subject having a microbial infection, or at risk of infection from a microorganism, such as a bacterium. The microbial infection may be a bacterial infection such as a Gram-negative bacterial infection.
Examples of Gram-negative bacteria include, but are not limited to, Escherichia spp., Klebsiella spp., Enterobacter spp., Salmonella spp., Shigella spp., Citrobacter spp., Morganella morganii. Yersinia pseudotuberculosis and other Enterobacteriaceae,
Pseudomonas spp., Acinetobacter spp., Moraxe!la, Helicobacter, Stenotrophomonas, Bdellovibrio, acetic acid bacteria, Legionella and alpha-proteobacteria such as Wolbachia and numerous others. Medically relevant Gram-negative cocci include three organisms, which cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis).
Medically relevant Gram-negative bacilli include a multitude of species. Some of them primarily cause respiratory problems (Hemophilus influenzae, Klebsiella pneumoniae,
Legionella pneumophila, Pseudomonas aeruginosa), primarily urinary problems (Escherichia coli, Enterobacter cloacae), and primarily gastrointestinal problems (Helicobacter pylori. Salmonella enterica). Gram-negative bacteria associated with nosocomial infections include Acinetobacter baumannii, which causes bacteremia, secondary meningitis, and ventilator-associated pneumonia in intensive-care units of hospital establishments.
In one embodiment the Gram-negative bacterial species is selected from the group consisting of £. coli, S. enterica, K. pneumoniae, K. oxytoca; E. cloacae, E. aerogenes, E. agglomerans, A. calcoaceticus, A. baumannii; Pseudomonas aeruginosa,
Stenotrophomonas maltophila, Providencia stuartii, P. mirabilis, and P. vulgaris.
In one embodiment the Gram-negative bacterial species is selected from the group consisting of E. coli, K. pneumoniae, Pseudomonas aeruginosa, and A. baumannii.
The compounds of formula (III) or compositions comprising the same are useful for the treatment of skin and soft tissue infections, gastrointestinal infection, urinary tract infection, pneumonia, sepsis, intra-abdominal infection and obstetrical/gynaecological infections. The infections may be Gram-positive or Gram-negative bacterial infections.
The compounds of formula (III) or compositions comprising the same are useful for the treatment of Pseudomonas infections including P. aeruginosa infection, for example skin and soft tissue infections, gastrointestinal infection, urinary tract infection, pneumonia and sepsis.
The compounds of formula (III) or compositions comprising the same are useful for the treatment of Acinetobacter infections including A. baumanii infection, for pneumonia, urinary tract infection and sepsis.
The compounds of formula (III) or compositions comprising the same are useful for the treatment of Klebsiella infections including K. pneumoniae infection, for pneumonia, urinary tract infection, meningitis and sepsis.
The compounds of formula (III) or compositions comprising the same are useful for the treatment of E. coli infection including E. coli infections, for bacteremia, cholecystitis, cholangitis, urinary tract infection, neonatal meningitis and pneumonia. Treatment
The term "treatment," as used herein in the context of treating a condition, pertains generally to treatment and therapy, whether of a human or an animal (e.g., in veterinary applications), in which some desired therapeutic effect is achieved, for example, the inhibition of the progress of the condition, and includes a reduction in the rate of progress, a halt in the rate of progress, alleviation of symptoms of the condition, amelioration of the condition, and cure of the condition. Treatment as a prophylactic measure (i.e., prophylaxis) is also included. For example, use with patients who have not yet developed the condition, but who are at risk of developing the condition, is encompassed by the term "treatment."
The term "therapeutically-effective amount," as used herein, pertains to that amount of a compound, or a material, composition or dosage form comprising a compound, which is effective for producing some desired therapeutic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.
The term "treatment" includes combination treatments and therapies, as described herein, in which two or more treatments or therapies are combined, for example, sequentially or simultaneously. Combination Therapy
A compound of formula (III) may be administered in conjunction with an active agent.
Administration may be simultaneous, separate or sequential.
The methods and manner of administration will depend on the pharmacokinetics of the compound of formula (III) and the second agent.
By "simultaneous" administration, it is meant that a compound of formula (III) and a second agent are administered to a subject in a single dose by the same route of administration.
By "separate" administration, it is meant that a compound of formula (III) and a second agent are administered to a subject by two different routes of administration which occur at the same time. This may occur for example where one agent is administered by infusion and the other is given orally during the course of the infusion.
By "sequential" it is meant that the two agents are administered at different points in time, provided that the activity of the first administered agent is present and ongoing in the subject at the time the second agent is administered.
Generally, a sequential dose will occur such that the second of the two agents is
administered within 48 hours, preferably within 24 hours, such as within 12, 6, 4, 2 or 1 hour(s) of the first agent. Alternatively, the active agent may be administered first, followed by the compound of formula (III).
Ultimately, the order and timing of the administration of the compound and second agent in the combination treatment will depend upon the pharmacokinetic properties of each.
The amount of the compound of formula (III) to be administered to a subject will ultimately depend upon the nature of the subject and the disease to be treated. Likewise, the amount of the active agent to be administered to a subject will ultimately depend upon the nature of the subject and the disease to be treated.
Formulations
In one aspect, the present invention provides a pharmaceutical composition comprising a compound of formula (III) together with a pharmaceutically acceptable carrier. The pharmaceutical composition may additionally comprise a second active agent. In an alternative embodiment, where a second agent is provided for use in therapy, the second agent may be separately formulated from the compound of formula optionally (III). The comments below made in relation to the compound of formula optionally (III) may therefore also apply to the second agent, as separately formulated. While it is possible for the compound of formula (III) to be administered alone or together with the second agent, it is preferable to present it as a pharmaceutical formulation (e.g., composition, preparation, medicament) comprising at least one compound of formula (III), as described herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, including, but not limited to, pharmaceutically acceptable carriers, diluents, excipients, adjuvants, fillers, buffers, preservatives, antioxidants, lubricants, stabilisers, solubilisers, surfactants (e.g., wetting agents), masking agents, colouring agents, flavouring agents, and sweetening agents. The formulation may further comprise other active agents, for example, other therapeutic or prophylactic agents.
Thus, the present invention further provides pharmaceutical compositions, as defined above, and methods of making a pharmaceutical composition comprising admixing at least one compound of formula (III), as described herein, together with one or more other
pharmaceutically acceptable ingredients well known to those skilled in the art, e.g., carriers, diluents, excipients, etc. If formulated as discrete units (e.g., tablets, etc.), each unit contains a predetermined amount (dosage) of the compound. The composition optionally further comprises the second active agent in a predetermined amount. The term "pharmaceutically acceptable," as used herein, pertains to compounds,
ingredients, materials, compositions, dosage forms, etc., which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of the subject in question (e.g., human) without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. Each carrier, diluent, excipient, etc. must also be "acceptable" in the sense of being compatible with the other ingredients of the formulation.
Suitable carriers, diluents, excipients, etc. can be found in standard pharmaceutical texts, for example, Remington's Pharmaceutical Sciences, 18th edition, Mack Publishing Company, Easton, Pa., 1990; and Handbook of Pharmaceutical Excipients, 5th edition, 2005.
The formulations may be prepared by any methods well known in the art of pharmacy. Such methods include the step of bringing into association the compound of formula (III) with a carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the compound with carriers (e.g., liquid carriers, finely divided solid carrier, etc.), and then shaping the product, if necessary.
The formulation may be prepared to provide for rapid or slow release; immediate, delayed, timed, or sustained release; or a combination thereof. Formulations may suitably be in the form of liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions (e.g., oil-in-water, water-in-oil), elixirs, syrups, electuaries, mouthwashes, drops, tablets (including, e.g., coated tablets), granules, powders, losenges, pastilles, capsules (including, e.g., hard and soft gelatin capsules), cachets, pills, ampoules, boluses, suppositories, pessaries, tinctures, gels, pastes, ointments, creams, lotions, oils, foams, sprays, mists, or aerosols.
Formulations may suitably be provided as a patch, adhesive plaster, bandage, dressing, or the like which is impregnated with one or more compounds and optionally one or more other pharmaceutically acceptable ingredients, including, for example, penetration, permeation, and absorption enhancers. Formulations may also suitably be provided in the form of a depot or reservoir.
The compound may be dissolved in, suspended in, or admixed with one or more other pharmaceutically acceptable ingredients. The compound may be presented in a liposome or other microparticulate which is designed to target the compound, for example, to blood components or one or more organs. Where a liposome is used, it is noted that the liposome may contain both the compound of formula (III) and the second agent. Formulations suitable for oral administration (e.g., by ingestion) include liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions (e.g., oil-in-water, water-in-oil), elixirs, syrups, electuaries, tablets, granules, powders, capsules, cachets, pills, ampoules, boluses. Formulations suitable for buccal administration include mouthwashes, losenges, pastilles, as well as patches, adhesive plasters, depots, and reservoirs. Losenges typically comprise the compound in a flavoured basis, usually sucrose and acacia or tragacanth. Pastilles typically comprise the compound in an inert matrix, such as gelatin and glycerin, or sucrose and acacia. Mouthwashes typically comprise the compound in a suitable liquid carrier.
Formulations suitable for sublingual administration include tablets, losenges, pastilles, capsules, and pills.
Formulations suitable for oral transmucosal administration include liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions (e.g., oil-in- water, water-in-oil), mouthwashes, losenges, pastilles, as well as patches, adhesive plasters, depots, and reservoirs.
Formulations suitable for non-oral transmucosal administration include liquids, solutions (e.g., aqueous, non-aqueous), suspensions (e.g., aqueous, non-aqueous), emulsions
(e.g., oil-in-water, water-in-oil), suppositories, pessaries, gels, pastes, ointments, creams, lotions, oils, as well as patches, adhesive plasters, depots, and reservoirs. Formulations suitable for transdermal administration include gels, pastes, ointments, creams, lotions, and oils, as well as patches, adhesive plasters, bandages, dressings, depots, and reservoirs.
Tablets may be made by conventional means, e.g., compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the compound in a free-flowing form such as a powder or granules, optionally mixed with one or more binders (e.g., povidone, gelatin, acacia, sorbitol, tragacanth, hydroxypropylmethyl cellulose); fillers or diluents (e.g., lactose, microcrystalline cellulose, calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc, silica); disintegrants (e.g., sodium starch glycolate, cross-linked povidone, cross-linked sodium carboxymethyl cellulose); surface-active or dispersing or wetting agents (e.g., sodium lauryl sulfate); preservatives (e.g., methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, sorbic acid); flavours, flavour enhancing agents, and sweeteners. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the compound therein using, for example, hydroxypropylmethyl cellulose in varying proportions to provide the desired release profile. Tablets may optionally be provided with a coating, for example, to affect release, for example an enteric coating, to provide release in parts of the gut other than the stomach.
Ointments are typically prepared from the compound and a paraffinic or a water-miscible ointment base.
Creams are typically prepared from the compound and an oil-in-water cream base. If desired, the aqueous phase of the cream base may include, for example, at least about 30% w/w of a polyhydric alcohol, i.e., an alcohol having two or more hydroxy I groups such as propylene glycol, butane-1.3-diol, mannitol, sorbitol, glycerol and polyethylene glycol and mixtures thereof. The topical formulations may desirably include a compound which enhances absorption or penetration of the compound through the skin or other affected areas. Examples of such dermal penetration enhancers include dimethylsulfoxide and related analogues. Emulsions are typically prepared from the compound and an oily phase, which may optionally comprise merely an emulsifier (otherwise known as an emulgent), or it may comprises a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil. Preferably, a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabiliser. It is also preferred to include both an oil and a fat. Together, the
emulsifier(s) with or without stabiliser(s) make up the so-called emulsifying wax, and the wax together with the oil and/or fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations. Suitable emulgents and emulsion stabilisers include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate and sodium lauryl sulfate. The choice of suitable oils or fats for the formulation is based on achieving the desired cosmetic properties, since the solubility of the compound in most oils likely to be used in pharmaceutical emulsion formulations may be very low. Thus the cream should preferably be a non-greasy, non-staining and washable product with suitable consistency to avoid leakage from tubes or other containers. Straight or branched chain, mono- or dibasic a Iky I esters such as di-isoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a blend of branched chain esters known as Crodamol CAP may be used, the last three being preferred esters. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and/or liquid paraffin or other mineral oils can be used.
Formulations suitable for intranasal administration, where the carrier is a liquid, include, for example, nasal spray, nasal drops, or by aerosol administration by nebuliser, include aqueous or oily solutions of the compound. As an alternative method of administration, a dry powder delivery may be used as an alternative to nebulised aerosols.
Formulations suitable for intranasal administration, where the carrier is a solid, include, for example, those presented as a coarse powder having a particle size, for example, in the range of about 20 to about 500 microns which is administered in the manner in which snuff is taken, i.e., by rapid inhalation through the nasal passage from a container of the powder held close up to the nose.
Formulations suitable for pulmonary administration (e.g., by inhalation or insufflation therapy) include those presented as an aerosol spray from a pressurised pack, with the use of a suitable propellant, such as dichlorodifluoromethane, trichlorofluoromethane, dichoro- tetrafluoroethane, carbon dioxide, or other suitable gases. Additionally or alternatively, a formulaton for pulmonary administration may be formulated for administration from a nebuliser or a dry powder inhaler. For example, the formulation may be provided with carriers or liposomes to provide a suitable particle size to reach the appropriate parts of the lung, to aid delivery of an appropriate does to enhance retention in the lung tissue.
Formulations suitable for ocular administration include eye drops wherein the compound is dissolved or suspended in a suitable carrier, especially an aqueous solvent for the compound. Formulations suitable for rectal administration may be presented as a suppository with a suitable base comprising, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols, for example, cocoa butter or a salicylate; or as a solution or suspension for treatment by enema.
Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the compound, such carriers as are known in the art to be appropriate.
Formulations suitable for parenteral administration (e.g., by injection), include aqueous or non-aqueous, isotonic, pyrogen-free, sterile liquids (e.g., solutions, suspensions), in which the compound is dissolved, suspended, or otherwise provided (e.g., in a liposome or other microparticulate). Such liquids may additional contain other pharmaceutically acceptable ingredients, such as anti-oxidants, buffers, preservatives, stabilisers, bacteriostats, suspending agents, thickening agents, and solutes which render the formulation isotonic with the blood (or other relevant bodily fluid) of the intended recipient. Examples of excipients include, for example, water, alcohols, polyols, glycerol, vegetable oils, and the like.
Examples of suitable isotonic carriers for use in such formulations include Sodium Chloride Injection, Ringer's Solution, or Lactated Ringer's Injection. Typically, the concentration of the compound in the liquid is from about 1 ng/mL to about 100 pg/mL, for example from about 10 ng/mL to about 10 g/mL, for example from about 10 ng/mL to about 1 g/mL. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets.
Dosage
Generally, the methods of the invention may comprise administering to a subject an effective amount of a compound of formula (III) so as to provide an antimicrobial effect. The compound of formula (III) may be administered at an amount sufficient to potentiate the activity of a second active agent. The second active agent is administered to a subject at an effective amount so as to provide an antimicrobial effect.
It will be appreciated by one of skill in the art that appropriate dosages of the compound of formula (III) or the active agent, and compositions comprising the compound of formula (III) or the active agent, can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of therapeutic benefit against any risk or deleterious side effects. The selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound of formula (III) or the active agent, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and/or materials used in combination, the severity of the condition, and the species, sex, age, weight, condition, general health, and prior medical history of the patient. The amount of compound of formula (III) or the active agent and route of administration will ultimately be at the discretion of the physician, veterinarian, or clinician, although generally the dosage will be selected to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects.
Administration can be effected in one dose, continuously or intermittently (e.g., in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of the therapy, the target cell(s) being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician, veterinarian, or clinician. In general, a suitable dose of a compound of formula (III) or the active agent is in the range of about 10 pg to about 250 mg (more typically about 100 g to about 25 mg) per kilogram body weight of the subject per day. Where the compound of formula (III) or the active agent is a salt, an ester, an amide, a prodrug, or the like, the amount administered is calculated on the basis of the parent compound and so the actual weight to be used is increased proportionately.
Kits
One aspect of the invention pertains to a kit comprising (a) a compound of formula (III), or a composition comprising a compound as defined in any one of formula (III), e.g., preferably provided in a suitable container and/or with suitable packaging; and (b) instructions for use, e.g., written instructions on how to administer the compound or composition.
The written instructions may also include a list of indications for which the compound of formula (III) is a suitable treatment.
In one embodiment, the kit further comprises (c) a second active agent, or a composition comprising the second active agent. Here, the written instructions may also include a list of indications for which the second active agent, together with the compound of formula (III), is suitable for treatment. Routes of Administration
A compound of formula (III), a second agent, or a pharmaceutical composition comprising the compound of formula (III) may be administered to a subject by any convenient route of administration, whether systemically/peripherally or topically (i.e., at the site of desired action).
Routes of administration include, but are not limited to, oral (e.g., by ingestion); buccal;
sublingual; transdermal (including, e.g., by a patch, plaster, etc.); transmucosal (including, e.g., by a patch, plaster, etc.); intranasal (e.g., by nasal spray); ocular (e.g., by eyedrops); pulmonary (e.g., by inhalation or insufflation therapy using, e.g., via an aerosol, e.g., through the mouth or nose); rectal (e.g., by suppository or enema); vaginal (e.g., by pessary);
parenteral, for example, by injection, including subcutaneous, intradermal, intramuscular, intravenous, intraarterial, intracardiac, intrathecal, intraspinal, intracapsular, subcapsular, intraorbital, intraperitoneal, intratracheal, subcuticular, intraarticular, subarachnoid, and intrasternal; by implant of a depot or reservoir, for example, subcutaneously or
intramuscularly.
The Subject/Patient
The subject/patient may be a chordate, a vertebrate, a mammal, a placental mammal, a marsupial (e.g., kangaroo, wombat), a rodent (e.g., a guinea pig, a hamster, a rat, a mouse), murine (e.g., a mouse), a lagomorph (e.g., a rabbit), avian (e.g., a bird), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., a horse), porcine (e.g., a pig), ovine (e.g., a sheep), bovine (e.g., a cow), a primate, simian (e.g., a monkey or ape), a monkey (e.g., marmoset, baboon), an ape (e.g., gorilla, chimpanzee, orang-utan, gibbon), or a human. Furthermore, the subject/patient may be any of its forms of development, for example, a foetus.
In one preferred embodiment, the subject/patient is a human.
It is also envisaged that the invention may be practised on a non-human animal having a microbial infection. A non-human mammal may be a rodent. Rodents include rats, mice, guinea pigs, chinchillas and other similarly-sized small rodents used in laboratory research. Methods of Preparation
Compounds of formula (III) can be prepared by conventional peptide synthesis, using methods known to those skilled in the art. Suitable methods include solution-phase synthesis such as described by Yamada et al, J. Peptide Res. 64, 2004, 43-50, or by solid-phase synthesis such as described by de Visser et al, J. Peptide Res, 61 , 2003, 298- 306, and Vaara et al, Antimicrob. Agents and Chemotherapy, 52, 2008. 3229-3236. These methods include a suitable protection strategy, and methods for the cyclisation step. Alternatively, compounds may be prepared from readily available polymyxins, for example by removal of the N-terminal amino acid of the polymyxin (residue 1 ). Such a method is described herein for the preparation of compounds based on residues 2-10 of polymyxins B and E.
As shown herein, it is possible to derivatise the N terminal group of a deacylated polymyxin compound, such as deacylated polymyxin B and deacylated polymyxin B nonapeptide, without derivatising the amino groups that are present in the side chains of the polymyxin compound. As described herein, the side chains of the polymyxin compound may be selectively protected without protecting the N terminal group. The N terminal group may then be reacted to provide the appropriate N terminal substituent. The side chain protection may subsequently be removed.
A protected Polymyxin can also be cleaved to the corresponding hepta peptide by cleavage of amino acids 1 -3. Methods for this cleavage are described in WO 2012/168820, and WO 1988/00950. As shown herein this can be derivatised by coupling to appropriately substituted dipeptides or tripeptides to provide novel polymyxin derivatives.
Other Preferences
Each and every compatible combination of the embodiments described above is explicitly disclosed herein, as if each and every combination was individually and explicitly recited.
Various further aspects and embodiments of the present invention will be apparent to those skilled in the art in view of the present disclosure.
"and/or" where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example "A and/or B" is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein.
Unless context dictates otherwise, the descriptions and definitions of the features set out above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments which are described. Where technically appropriate embodiments may be combined and thus the disclosure extends to all permutations and combinations of the embodiments provided herein.
Certain aspects and embodiments of the invention will now be illustrated by way of example and with reference to the figures described above. Abbreviations
Abbreviation Meaning
PMBN Polymyxin B nonapeptide PMB Polymyxin B
Thr Threonine
Ser Serine
DSer D-serine
Leu Leucine
lie Isoleucine
Phe Phenylalanine
Dphe D-phenylalanine
Val Valine
Dab α,γ-Diaminobutyric acid DIPEA A/,A/-diisopropylethylamine
1 -(Boc-oxyimino)-2-phenyl
BOC-ON
acetonit ile
1 -ethyl-3-(3- EDC octaminopropyl)carbodiimide hydrochloride
(Benzotriazol-1-yl-
PyBOP oxy)tripyrrolidinophosphonium hexafluorophosphate 2-(7-aza-1 H-benzotriazol-1-yl)-
HATU 1 , 1 -3,3-tetramethyluronium hexafluorophosphate
HOAt 1-Hydroxy-7-azabenzotriazole DCM Dichloromethane TFA Trifluoroacetic acid ND Not determined
N/A Not applicable
DMF N.N-Dimethylformamide PMBH Polymyxin B heptapeptide (3-10) PMBD Polymyxin B decapepide Pro Proline
Dap α.β-Diaminopropionic acid Gly Glycine
Thr Threonine
His Histidine
Phe Phenylalanine Examples
The following examples are provided solely to illustrate the present invention and are not intended to limit the scope of the invention, as described herein.
Nomenclature - Compounds are named based on the natural polymyxin core from which they are synthetically derived.
Synthesis Examples
Intermediate 1 - Polymyxin B nonapeptide
A mixture of EDTA (1.4 g), potassium chloride (1.1 g) and L-cysteine (0.12 g) was dissolved in water (475 mL) and potassium phosphate buffer (pH 7, 25 mL). The reaction was stirred at 37 C for 10 min then Polymyxin B (10.3 g) was added. After stirring for 2h at 37 °C papain (3.36 U/ mg) was added and stirred for a further 18h at 37 C The progress of the reaction was monitored by LC-MS using the conditions outlined in Table 1 . The crude material was separated into 87 mL fractions and purified using 10 g SCX cartridge (* 6), eluting first with methanol (100 mL) and then 20% ammonia (aq, sp.g.880) in methanol (100 mL). The ammonia fractions were isolated and evaporated to give the product as beige solid, yield 4.95 g, 60% m/z 482, [M+2H]2' .
Table 1 - LC-MS conditions
Micromass Platform LC
Column: Zorbax 5μ C18 (2) 150 x 4.6 mm
Mobile Phase A: 10% Acetonitrile in 90% Water, 0.15 %TFA or 0.1 % formic
Mobile Phase B: 90% Acetonitrile in 10% Water, 0.15 %TFA or 0.1 % formic
Flow rate: 1 mL/min
Gradient: Time 0 min 100% A 0% B
Time 10 min 0% A 100% B
Time 1 1 min 0% A 100% B
Time 1 1.2 min 100% A 0% B
Time 15 min 100% A 0% B
Cycle time 15 min
Injection volume: 20 pL
Detection: 210 nm
Intermediate 2 - Tetra-(Boc) Polymyxin B nonapeptide
Selective BOC protection of the free γ-amino groups on the Dab residues of polymyxin I nonapaptide was carried out using the procedure of H. O'Dowd et al, Tetrahedron Lett., 2007, 48, 2003-2005. Polymyxin B Nonapeptide (Intermediate 1 1.00 g, 1.0 mmol) was dissolved in water (4.4 mL), dioxane (4.4 mL), triethylamine (4.4 mL) and the mixture was stirred for 10 min prior to the addition of 1-(Boc-oxyimino)-2-phenyl acetonitrile (Boc-ON) (0.77 g; 3.1 1 mmol). After stirring for 18 h, a further addition of Boc-ON (0.1 g, 0.4 mmol) was added and the mixture was stirred for a further 3 h. The progress of the reaction was followed by LC-MS, once complete the mixture was quenched by the addition of 20% methanolic ammonia (50 mL). The mixture was then evaporated to dryness and re-dissolved in methanol which was subsequently loaded onto silica. The crude material was purified using chromatography (eluent 0-20% methanol in dichloromethane) on silica gel (40 g) to afford tetra-(Boc) polymyxin B nonapeptide as a white solid (0.5 g, 36 %). TLC, Rf 0.2 (10% methanol in dichloromethane). m/z 1362.8[MH]\
Intermediate 3 - Colistin (Polymyxin E) nonapeptide Colistin (polymyxin E, 5 g) was treated with immobilised papain (185 ELU/g), potassium phosphate buffer (25 rriM; pH 7, 1 .25 L), potassium chloride (30 mM), EDTA (10 mM) and cysteine (1 mM) at 37°C for 32 h with gentle agitation to produce colistin (polymyxin E) nonapeptide. The progress of the reaction was monitored by LC-MS using the conditions outlined in Intermediate 1 , Table 1. The immobilized papain was removed by filtration and the filtrate was concentrated in vacuo to leave a solid residue which was re-suspended in 10% aqueous methanol and left at room temperature overnight. The supernatant was decanted and concentrated in vacuo. Colistin (Polymyxin E) nonapeptide was purified from the residue by SPE on C18 silica (10 gm), eluting with 0-25% aqueous methanol.
Evaporation of the appropriate fractions gave the product as a white solid, m/z 465.32
[M+2H]2+.
Intermediate 4 - Tetra-(Boc) Colistin (Polymyxin E) nonapeptide
Colistin (Polymyxin E) Nonapeptide (2.5 g, 2.69 mmol) was suspended in water (35 mL) with sonication. Dioxane (35 mL) and triethylamine (35ml) were added and the mixture was cooled in ice for 10 min prior to the addition of 1-(Boc-oxyimino)-2-phenyl acetonitrile (Boc-ON) (2.65 g; 10.76 mmol). The progress of the reaction was followed by LC-MS and reached completion after 10 minutes, whereupon the mixture was quenched by addition of 20% methanolic ammonia (25 mL). The liquid phase was decanted and the residual solid was re-dissolved in water and extracted sequentially with dichloromethane and iso-butanol. Based on LC-MS analysis, the decanted liquid and both dichloromethane and iso-butanol extracts were pooled together followed by concentration in vacuo to give yellow gum which was loaded onto flash chromatography (Si 6 OA- 35-70). The column was eluted with 0-20% methanol (containing 2% ammonia) in dichloromethane. The column fractions eluted with 7-10% methanol (containing 2% ammonia) in dichloromethane afforded tetra-(Boc) colistin (polymyxin E) nonapeptide as a white solid (1 .18 g, 33 %). m/z 1329.7 [M+H]\ Intermediate 5 - Tri-(Boc) Polymyxin B heptapeptide
PMB sulphate (2 g) was dissolved in water (20 mL) followed by addition of 1 ,4 dioxane (40 mL) and left to stir for 10 minutes at room temperature. To the reaction mixture was added Boc anhydride (4.42 g) was added as solid and the reaction was stirred at room temperature and was monitored by HPLC. The reaction mixture was then adjusted to pH 6 using 1 M HCI , the precipitate which formed was filtered and washed with water (50 mL) and heptane (50 mL), to leave BocsPMB as a white solid (2.4 g, 85 %). This material (1 g) was dissolved in 1 ,4-butanediol (1 12.5 mL) and the mixture was stirred at 40 C overnight. To the solution potassium phosphate (75 mL, 0.12 5M pH 8.0) was added over one minute, causing the formation of a white suspension. The reaction was diluted by adding 1 12.5 mL butanediol and 75 mL potassium phosphate (0.125 M pH 8.0), but the white emulsion persisted. The temperature of the reaction was reduced to 37 C and then Savinase 16L (250 L) was added and the reaction was stirred at room temperature overnight. As the reaction progressed the white emulsion cleared to form a transparent solution due to the formation of the more soluble PMBH-B0C3. The reaction mixture was diluted with water (50ml) and was then extracted with DCM (100 mL) The DCM layer was collected and evaporated in vacuo to afford a colourless oil. The resulting oil was diluted in 50 % methanol (aq.) and was loaded onto four preconditioned 10 g Varian Bond Elut SCX cartridges and the flow through was collected. The cartridges were washed with two column volumes of 50 % methanol (aq.) and then PMBH-B0C3 was eluted from the column using two column volumes of 20% ammonia in methanol. The resulting eluent was evaporated to dryness in vacuo to afford purified PMBH-Boc3 (610 mg). m/z 1062.6 [M+H]\ Intermediate 7 - Thr(0JBu) Tetra-(N-Boc) Polymyxin B nonapeptide
Step 1 - (S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy-butyrylamino)-4-tert- butoxycarbonylamino-butyric acid methyl ester To a stirred suspension of (S)-2-Benzyloxycarbonylamino-3-tert-butoxy-butyric acid DHCA salt (3.65 g, 7.4 mmol) and (S)-2-Amino-4-tert-butoxycarbonylamino-butyric acid methyl ester HCI salt (2.0 g, 7.4 mmol) in a mixture of DCM (60 mL) and DMF (120 mL) was added N,N-diisopropylethylamine (3.85 mL, 22.1 mmol). To this stirred mixture was added
1-hydroxy-7-azabenzotriazole (1 .0 g, 7.3 mmol) followed by N-(3-dimethylaminopropyl)-N'- ethyl carbodiimide HCI salt (1 .42 g, 7.4 mmol). The mixture was stirred for 17 h at ambient temperature then filtered under suction to remove the insoluble by-product, which was discarded. The filtrate was concentrated to a yellow oil which was partitioned between a solvent mixture of EtOAc/Et20 (1 :1 ) (250 mL) and 0.5 M hydrochloric acid (200 mL). The aqueous phase was re-extracted with fresh solvent mixture (100 mL) and the combined organic extracts were successively washed with water (150 mL) and sat. NaHCOa solution (150 mL), dried (Na2S04) and concentrated to a colourless oil (3.72g). This oil was purified by silica gel chromatography on a 100g SepPak cartridge, eluting with a solvent gradient of EtOAc/i-hexane (0-70%). Fractions containing the product (Rf 0.26 in EtOAc/i-hexane 3:7, visualized with KMnC spray) were pooled and concentrated to give the title compounds as a colourless foam (3.58 g, 6.8 mmol, 92% yield), m/z 524 (MH+, 100%). Step 2 - (S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy-butyrylamino)-4-tert- butoxycarbonylamino-butyric acid
A solution of lithium hydroxide monohydrate (0.861 g, 20.5 mmol) in water (16 mL) was added to a stirred solution of (S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy- butyrylamino)-4-tert-butoxycarbonylamino-butyric acid methyl ester (3.58 g, 6.8 mmol) in methanol (64 mL) at ambient temperature and stirred for 19 h. To this solution was added 1 M HCI (24 mL) resulting in a milky mixture (pH 1 ) which was quickly extracted with DCM (3 x 135 mL). The combined organic extract was dried (NazSC^) and concentrated to give the title compound as a colourless foam (3.27 g, 6.4 mmol, 94% yield). M/z 532 [MNa]+, 1041 [2M+Na]+.
Step 3 - CbzHNPMBN(OBu)(Boc)4
(S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy-butyrylamino)-4-tert- butoxycarbonylamino-butyric acid (1.73 g, 3.39 mmol) and Intermediate 5 (3.0 g, 2.8 mmol) were charged to a flask to which dry DCM (85 ml) and dry DMF (17 mL) were added with stirring. To the stirred solution was added Λ/./V-diisopropylethylamine (1 .46ml, 8.4mmol) and after stirring for 5 min., 0-(7-azabenzotriazol-1-yl)-N,N.N'N'-tetramethyluronium hexafluorophosphate (1.29 g, 3.39 mmol) was added in a single portion. The mixture was sonicated for 2 minutes then left to stir at ambient temperature for 18 h. The reaction mixture was then evaporated and the residue re-evaporated from toluene (3 x 100 mL). The residue was dried under vacuum for 3 h to ensure removal of toluene. Water (50ml) was added to this material and the mixture was rapidly stirred for 3 h with occasional sonication. The title compound was collected by suction filtration as a fine, white solid and washed with water (2 x 25 mL) then dried under vacuum for 15h (4.6 g, 3.0 mmol, 100% yield), m/z 1554[MH+].
Step 4 - Title Compound The product from step 3 (5.41 g, 3.48 mmol), ammonium formate (6.6 g, 104.4 mmol) and 10% Pd-C (2.0 g) were charged to a flask under N2. MeOH (270 mL) was added and the mixture was stirred under N2 for 4.5h. LCMS showed MH+ for product and loss of starting material. The mixture was filtered under suction through a pad of celite and washed through with MeOH (50 mL). The filtrate and washings were evaporated to a colourless oil which was partitioned between a solvent mixture of EtOAc/MeOH (4:1 )(250 mL) and water
(250 mL). The aqueous phase was further extracted with the same, fresh solvent mixture (2 x 100 mL). The combined organic extracts were dried ( a2S04) and evaporated to a colourless oil (~ 6g). This material was purified by chromatography on silica gel (100 g SepPak column) eluting with a gradient of MeOH/EtOAc (0-4%). Fractions containing the product (Rf 0.30 in EtOAc/MeOH/NH4OH 8so 95:5:1 , visualized with KMn04 spray) were pooled and evaporated to give the title compound as a crispy foam (4.0g, 2.8mmol, 81 % yield), m/z 1420 [MH+].
Intermediate 9 - Tri-(BOC)-Polymyxin E heptapeptide
Figure imgf000071_0001
Colistin sulphate (5.0 g, 3.95 mmol) was dissolved in acetonitrile (50 mL) and water (25 mL) and stirred at room temperature for 10 minutes. Triethylamine (3.2 mL, 23.0 mmol) was added and the mixture stirred for a further 10 minutes. Di-tert-butyl dicarbonate (5.0 g, 23.0 mmol) was subsequently added in one portion and the mixture stirred for 16 hours. Savinase (15 mL) was then added, followed by 4 M sodium hydroxide solution (0.5 mL) and the reaction mixture stirred at room temperature for 5 days. The mixture was diluted with ethyl acetate and water. After separation of the layers, the organic phase was washed with 0.1 M sodium hydroxide solution (x2), then water. The organic layer was dried over magnesium sulphate, filtered and the solvent evaporated at reduced pressure. The residue was purified by silica gel chromatography eluting with 0 - 100% (80:20:2
EtOAc:MeOH:880NH3) in ethyl acetate to yield the title compound (2.28g, 56%). m/z 1028, [MH]+
Intermediate 10 - Thr(O-'Bu) Tetra-(N-Boc) Polymyxin E nonapeptide The title compound was prepared from fS)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy- butyrylamino)-4-tert-butoxycarbonylamino-butyric acid and Intermediate 9 according to the method for Intermediate 7 steps 3 and 4. m/z 1385, [MH]+ Intermediate 11 - Tetra- (N-Boc)-L-Thr(0-'Bu)-L-Dap-Polymyxin B heptapeptide
The title compound was prepared from (S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy- butyrylamino)-3-tert-butoxycarbonylamino-propionic acid and Intermediate 5 according to the method for Intermediate 7 steps 3 and 4. m/z 1405. [MH]'
Intermediate 12 - Tetra- (N-Boc)-L-Ser ( 0-'Bu)-L-Dap-Polymyxin B heptapeptide
The title compound was prepared from(S)-2-((S)-2-(((benzyloxy)carbonyl)amino)-3-(tert- butoxy)propanamido)-3-((tert-butoxycarbonyl)amino)propanoic acid and Intermediate 5 according to the method for Intermediate 7 steps 3 and 4. m/z 1391 [MH]'
Intermediate 13 -Tetra- (N-Boc)-L-Thr(0JBu)-D-Ser-Poiymyxin B heptapeptide The title compound was prepared from N-(N-((benzyloxy)carbonyl)-0-(tert-butyl)-L-threonyl)- 0-(tert-butyl)-D-serine and Intermediate 5 according to the method for Intermediate 7 steps 3 and 4. m/z 1362 [MH] '
Intermediate 14 - Tetra- (N-Boc)-L-Thr(0-'Bu)-L-Dap-Polymyxin E heptapeptide
The title compound was prepared from (S)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy- butyrylamino)-3-tert-butoxycarbonylamino-propionic acid and Intermediate 9 according to the method for Intermediate 7 steps 3 and 4. m/z 1372, [MH]' Intermediate 15 - Tetra- (N-Boc)-L-Thr(0-'Bu)-D-Dap-Poiymyxin B heptapeptide
The title compound was prepared from (R)-2-((S)-2-Benzyloxycarbonylamino-3-tert-butoxy- butyrylamino)-3-tert-butoxycarbonylamino-propionic acid and Intermediate 5 according to the method for Intermediate 7 steps 3 and 4. m/z 1406, [MH]'
Intermediate 16 - (S)-4-(Boc)amino-2-hydroxybutanoyi Thr(O-'Bu) Tetra-(N-Boc) polymyxin B nonapeptide [Thr- 10( O-triethylsilyl) ]
Step 1
Intermediate 7 (Thr(O-'Bu) Tetra-(N-Boc) Polymyxin B nonapeptide) (250 mg, 0.18 mmol) was dissolved in dichloromethane (2 ml_), treated with 2,6-lutidine (1 mL) and cooled to 0°C under a nitrogen atmosphere. The solution was treated dropwise with
(triethylsilyl)trifluoromethane sulphonate (0.26 mL, 3.3 equiv), then allowed to warm to room temperature overnight. The solution was quenched with saturated aqueous ammonium chloride solution (10 mL) and the product extracted into diethyl ether (2 x 20mL). The organic extracts were combined, dried over anhydrous magnesium sulphate and evaporated under reduced pressure. The residue was chromatographed on silica eluting with 0-20% (10%ammonia in methanol) in dichloromethane. Product-containing fractions were combined and evaporated to a white solid (1 17 mg, 43%). 400MHz Ή nmr (CDCI3)(/nter alia) 0.46 (6H, q, SiCH2).0.80-0.88 (12H, m, incl t, SiCH2CH3), 1.12 (9H, s, O'Bu), 1.34-1.40 (36H, m, BOC).
Step 2
The triethyl silyl protected nonapeptide from Step 1 (1 17 mg) was reacted with (S)-4-((tert- butoxycarbonyl)amino)-2-hydroxybutanoic acid (33 mg) under the conditions described for coupling method 2A step 1 to afford the Title compound (95 mg, 71 %). 400 MHz 1H nmr (CDCI3)(/nier alia) 0.48 (6H, q, SiCH2).0.80-0.88 (12H, m, incl t, SiCH2CH3), 1 .22 (9H, s, O'Bu), 1 .36-1.42 (36H, m, BOC) .
Method 1 - General method of preparation of nonapeptide amide derivatives
Step 1. The corresponding carboxylic acid (5 equiv with respect to the polymyxin substrate) was dissolved in dichloromethane (2 mL/mmol). A/,A/-Diisopropylethyalmine (5.0 equiv.) and 2-(1 H-7-Azabenzotriazol-1 -yl)-1 , 1.3, 3-tetra methyl uronium hexafluorophosphate (HATU) (5.0 equiv ) were then added to the reaction mixture. After 30 min stirring at room temperature compound of intermediate 2 or intermediate 4 (1.0 equiv.) was added. After 16 h the completion of the reaction was confirmed by LC-MS and the reaction mixture was evaporated to dryness and purified using column chromatography on silica gel (eluent 0-10% methanol in dichloromethane). The appropriate fractions were concentrated to leave the product as a colourless oil (typical yield 58 %).
Step 2. The product from Step 1 was dissolved in dichloromethane (20 mL/mmol).
Trifluoroacetic acid (60 equiv.) was added and the mixture was stirred at room temperature for 16 h, after which time LC-MS confirmed completion of the reaction. The reaction mixture was concentrated in vacuo to leave the trifluoroacetate salt as a colourless oil. To this was added water (10 mL/mmol) and the mixture was sonicated for 5 min. To the resulting suspension was added 1 M NaHC03 until the mixture reached pH 9. The mixture was then passed through a 10 g C18 SPE column, eluting sequentially with 0, 40, 50, 60, 70, 80 and 100 % aqueous methanol. Product-containing fractions were pooled and evaporated. The residue was suspended in water and 0.1 M H2S04 added until pH 7 was reached. The solution was lyophilised overnight to afford the sulphate salt as a white solid. Compound purity was assessed by HPLC using the conditions outlined in Table 2. Table 2 - Analytical HPLC conditions
Column: Zorbax 5μ C18 (2) 150 x 4.6 mm
Mobile Phase A: 10% Acetonitrile in 90% Water, 0.15 %TFA or 0.1 % Formic acid
Mobile Phase B: 90% Acetonitrile in 10% Water, 0.15 %TFA or 0.1 % Formic acid
Flow rate: 1 mL/min
Gradient: Time 0 min 100% A 0% B
Time 10 min 0% A 100% B
Time 1 1 min 0% A 100% B
Time 1 1.2 min 100% A 0% B
Cycle time 15 min
Injection volume: 20 μί.
Detection: 210 nm Method 2 - General method of preparation of nonapeptide amides
Step 1 - The BOC protected nonapeptide was prepared using the conditions of Method 1. After completion if the reaction, the crude reaction mixture was adsorbed onto silica and chromatographed on a silica cartridge, eluting with 0-20% methanol in dichloromethane. Product-containing fractions were combined and evaporated to a white foam. The product thus obtained was re-purified by silica gel chromatography to obtain the product as a white foam.
Step 2 - The purified product from Step 2 was dissolved in dichloromethane (2 ml_), treated with TFA (1 mL) and the mixture stirred at room temperature for 1 hour. The solvent was evaporated and the residue azeotroped with toluene, to leave a white solid. This was dissolved in water (10 mL) and washed with dichloromethane (5 mL). The aqueous phase was evaporated to low volume and lyophilised overnight to afford the TFA salt of the product as a white solid.
Method 2A - Further General method of preparation of nonapeptide amides
Step 1 - The protected polymyxin substrate (0.07 mmol) was dissolved in dichloromethane (4 mL), and treated with the corresponding carboxylic acid (1 .5 equiv with respect to the polymyxin substrate), A/,A/-Diisopropylethyalmine (3.0 equiv.), followed by HATU
(2.0 equivalent). After 16 h the completion of the reaction was confirmed by LC-MS and the reaction mixture was evaporated to dryness. Water (-10 mL) was added and the mixture triturated then stirred vigorously for 1 h. The resultant precipitate was collected by filtration and dried in vacuo overnight.
Step 2 - The Boc-protected derivative from Step 1 was dissolved in dichloromethane (3 mL) and treated with TFA (1 mL). The reaction mixture was stirred at room temperature until LCMS confirmed complete deprotection. The solvent was evaporated and the residue chromatogaphed by prep HPLC using the conditions of Method 3, step 6. Product- containing fractions were combined, evaporated to low volume, and lyophilised to afford the product as the TFA salt.
Method 3 - General method for the preparation of dipeptide amide derivatives of polymyxin B heptapeptide
Step 1 - Coupling of carboxylic acids to methyl esters of amino acid 1
The appropriate carboxylic acid (1 .1 equiv.), the appropriate (N-Boc or OBu') amino acid methyl ester hydrochloride (1 equiv.), EDC hydrochloride (1 .1 equivs.) and HOAt (1 .1 equiv.) were charged to a flask. DCM (8 mL/mmol with respect to the amino acid methyl ester) was added and to the stirred mixture under nitrogen was added DI PEA (3 equiv.) to give a yellow solution. The solution was stirred for 18 h, diluted with an equal volume of DCM and the solution washed successively with water (16 mL/mmol with respect to amino acid) and sodium hydrogen carbonate solution (16 mL mmol). The solution was dried a2S04) and evaporated to a residue. The residue was purified by chromatography on silica gel (gradient elution with EtOAc/iso-hexane). Relevant fractions were pooled and evaporated to afford the desired methyl ester product (m/z [M+H] ' detectable in the LCMS spectrum). Where a racemic acid is used, the product is obtained as a mixture of diastereoisomers.
Step 2 - Hydrolysis of the methyl ester product from step 1 To a stirred solution of the product from step 1 (1 equiv.) in methanol (5 mL/mmol with respect to the methyl ester) was added a solution of lithium hydroxide monohydrate
(3 equiv.) in water (0.5 mL/mmol of reagent). The resulting solution was stirred at ambient temperature for 24 h then poured into water (25 mL/mmol with respect to methyl ester). This solution was adjusted to pH 1 by the addition of 1 M hydrochloric acid (3 equiv.) and the mixture was extracted with DCM (3 x). The combined organic extracts were dried (Na2SO.i) and evaporated to afford the desired carboxylic acid (m/z [M+H]* detectable in the LCMS spectrum) . Where a racemic acid is used in step 1 , the product is obtained as a mixture of diastereoisomers. Step 3: Coupling of the carboxylic acid product from step 2 with the methyl ester of amino acid 2
This step was carried out in the same manner as that described in step 1 , using the carboxylic acid from step 2 and the appropriate (N-Boc or OBu') amino acid methyl ester hydrochloride. The methyl ester product (m/z [M+H]+ detectable in the LCMS spectrum) was isolated as described in step 1 . Where a racemic acid was used in step 1 , the product is obtained as a mixture of diastereoisomers. Step 4 - Hydrolysis of the methyl ester product from step 3
This step was carried out in the same manner as that described in step 2, using the methyl ester from step 3. The carboxylic acid product (m/z [M+H]+ detectable in the LCMS spectrum) was isolated as a mixture of diastereoisomers.
Step 5 - Coupling of the carboxylic acid product from step 4 with Tri-(Boc) Polymyxin B hepta peptide (intermediate 5)
PyBoP (2 equiv.) was added to a stirred solution of the carboxylic acid from step 4 (2 equiv.) in dry DCM (15 mL/mmol with respect to acid). DI PEA (2 equiv.) was then added and the solution stirred for 30 min. To this solution was then added a solution of Intermediate 5 (1 equiv.) in dry DCM (12 mL/mmol with respect to acid) and dry DMF (1 .5 mL mmol with respect to acid) and the whole mixture was stirred for 16 h. The mixture was then evaporated to a thick oil which was partitioned between EtOAc and water. The organic phase was washed with saturated sodium hydrogen carbonate solution then brine, dried (Na2SO.i) and evaporated to a foam. The material was purified by chromatography on silica gel (gradient elution with MeOH/EtOAc) to afford the polypeptide product (m/z [M+H]* detectable in the LCMS spectrum). Where a racemic acid was used in step 1 , the product is obtained as a mixture of diastereoisomers.
Step 6 - Deprotection of the Polymyxin B heptapeptide product from step 5 TFA (30 mL/mmol with respect to polypeptide) was added to a stirred solution of the polypeptide from step 5 in DCM (60 mL/mmol). The solution was stirred for 3.5 h then evaporated and dried under vacuum for 1 h. The residue was purified by HPLC (conditions below) and lyophilised to afford the TFA salt of the product as a white solid. Where a racemic acid was used in step 1 , the product is obtained as a mixture of diastereoisomers. (See Table 4 for examples).
Table 3 - Prep HPLC conditions
Column: Sunfire C18 OBD 5pm x 30mm x 150mm
Mobile Phase A: Acetonitrile + 0.15 %TFA
Mobile Phase B: water + 0.15 %TFA
Flow rate: 25 mL/min
Gradient: Time 0 min 3% A 97% B
Time 2 min 3% A 97% B
Time 25 min 40% A 60% B
Time 30 min 97% A 3% B Time 32 min 97% A 3% B
Detection: 210 nm
Method 3A
The coupling was carried out as described in Method 3, using a CBZ-protected amino acid at Step 3. An additional CBZ deprotection step (Step 5A) was included prior to step 6.
Step 5A - CBZ Deprotection:
A mixture of the protected intermediate from Step 5 (0.0573mmol) and 10% Pd/C paste (10 mg) in ethanol (4 rrsL) was stirred under an atmosphere of hydrogen for 18 h. Further 10% Pd/C paste (10 mg) was added and stirring was continued for a further 24 h. The reaction mixture was filtered through a pad of celite and the filtercake was washed with ethanol (2 x). The combined organics were evaporated to afford a crude oil. This was purified by reverse phase preparatory HPLC using the conditions of Method 3 step 6 to afford the desired product as a colourless glass (20%). (m/z [M+H]+ detectable in the LCMS spectrum). Method 3B
Method 3B consists of steps 1-2 of Method 3A followed by coupling to BOC-protected PMBN (Intermediate 2) to give the protected deca peptide. Deprotection following Method 3A, Step 5A for CBZ deprotection and Step 6 for Boc deprotection affords the desired compound.
General Preparation of Acetate Salts.
A TFA salt (50 mg) was dissolved in water, and taken to pH 9 with 1 M NaHCOa. The mixture was then passed through a 1 g C18 SPE column, eluting with water (20 mL) followed by 80% methanol/water. Product-containing fractions were pooled treated with 0.1 M acetic acid (10 equiv.). The solution was concentrated under reduced pressure, then lyophilised overnight to afford the acetate salt as a white solid. Compound purity was assessed by HPLC using the conditions outlined in Table 2. Alternative Preparation of Acetate Salts
A TFA salt (20 mg) was dissolved in water (0.5 mg) and applied to a column of AG1-X2 resin (BioRad) (1 g, acetate form, pre-washed with 10% acetic acid in water, followed by 1 % acetic acid in water). The column was eluted with water (8 mL) and the eluant concentrated under reduced pressure, then lyophilised overnight to afford the acetate salt as a white solid (14 mg). Compound purity was assessed by 1 H NMR and HPLC using the conditions outlined in Table 2. Synthesis of Carboxylic Acids Carboxylic acids used for the assembly of polymyxin derivatives were secured either via commercial sources, or prepared using methods known to those skilled in the art.
Experimental details of the following carboxylic acids serve as representative examples for the synthesis of similar acid intermediates used in the synthesis of the compounds of the present invention.
Trans-1-tert-butoxycarbonyl-5-oct l-piperidine-3-carboxylic acid (relative stereochemistry)
Figure imgf000078_0001
(i) - Ethyl 5-oct-1-ynylpyridine-3-carboxylate
To a solution of ethyl-5-bromonicotinate (1 .15 g, 5.0 mmol) in ethyl acetate (20ml) under nitrogen was added triethylamine (1.1 ml_, 7.5 mmol), 1-octyne (1.1 ml_, 7.5 mmol), bis(triphenylphosphine)palladium (II) dichloride (176 mg, 0.25 mmol) and copper iodide (10 mg, 0.05 mmol). The reaction mixture was stirred at 50°C for 16 hours, then filtered under suction through Celite and washed through with ethyl acetate. The filtrate was evaporated at reduced pressure. The residue was purified by silica gel chromatography eluting with 0 - 50% ethyl acetate in iso-hexane to yield the title compound (1.20 g, 93%), m/z 260 (MH+), C16H21 N02 exact mass 259.157. (ii) - Ethyl 5-octylpiperidine-3-carboxylate
To a solution of ethyl 5-oct-1 -ynylpyridine-3-carboxylate (1.20 g, 4.60 mmol) in acetic acid (100 mL) was added platinum oxide (100 mg). The reaction mixture was hydrogenated for 16 h., then filtered under suction through Celite and washed through with ethyl acetate. The filtrate was evaporated at reduced pressure and then the residue was partitioned between ethyl acetate and water. The pH of the aqueous layer was adjusted to pH10 by the addition of .880 ammonia. After separation of the layers, the aqueous phase was re-extracted with ethyl acetate and then the combined organic layers were passed through a hydrophobic frit. The solvent was evaporated at reduced pressure and the residue purified by silica gel chromatography eluting with 0 - 100% (80:20:2 ethyl acetate:methanol:.880 ammonia) in ethyl acetate gave ethyl 5-octylpi peridi ne-3-ca rboxylate (876 mg, 71 %). m/z 270 (MH+), C16H31 N02 exact mass 269.235.
(iii) - Cis-01-tert-butyl 03-ethyl 5-octylpiperidine-1 ,3-dica rboxylate and frans-01-tert-butyl 03-ethyl 5-octylpiperidine-1 ,3-dicarboxylate (relative stereochemistry)
Figure imgf000079_0001
To a solution of ethyl 5-octylpiperidine-3-ca rboxylate (870mg, 3.20mmol) in dichloromethane (50 mL) was added triethylamine (680 μΙ_, 4.8 mmol), followed by di-tert-butyl dicarbonate (1 .06 g, 4.8 mmol). The reaction mixture was stirred at room temperature for 16 hours and then concentrated at reduced pressure. The residue was dissolved in diethyl ether and washed with ammonium chloride solution. After separation of the layers, the aqueous phase was re-extracted with diethyl ether. The combined organic phases were dried (MgS04), filtered and concentrated at reduced pressure. The products were purified by silica gel chromatography eluting with 0-30% diethyl ether in iso-hexane. The first product to elute was assigned cis stereochemistry (470 mg, 40%) {when compared to the cyclohexyl analogue in Syn Comm, 2008, 38, 2799}. m/z 314 (M-tBu) +. Further elution of the column gave the trans derivative (333mg, 28%). m/z 314 (M-tBu) +.
(iv) - Trans-1-tert-butoxycarbonyl-5-octyl-piperidine-3-carboxylic acid (relative
stereochemistry)
To a solution of trans -01 -tert-butyl 03-ethyl 5-octylpiperidine-1 ,3-dica rboxylate (330 mg, 0.89 mmol) in dioxane (5 mL) and water (2 mL) was added lithium hydroxide monohydrate (76 mg, 1.80 mmol). The reaction mixture was stirred at room temperature for 16 hours and then treated with a further quantity of lithium hydroxide monohydrate (100 mg) for 2 days. The reaction mixture was concentrated at reduced pressure and the residue partitioned between ethyl acetate and water. The aqueous phase was acidified by the addition of 1 M hydrochloric acid and the product extracted into ethyl acetate. The organic phase was passed through a hydrophobic frit and the solvent evaporated at reduced pressure to yield the title compound (275 mg, 91 %). m/z 342 (MH+), C19H35N04 exact mass 341.257. 2-(2-Tert-butoxycarbonylamino-ethyl)-undecanoic acid
Figure imgf000080_0001
(i) - 2-Cyanomethyl - undecanoic acid
THF (30 mL) was added to a stirred solution of n-butyl lithium (2.5 M in hexane, 9.4 mL, 23.5 mmol) at -78°C. To this solution was added diethylamine (0.5 mL, 4.8 mmol) over 2 minutes. The solution was warmed to 0°C for 15 minutes then recooled to -78°C. A solution of undecanoic acid (2.0 g, 10.7 mmol) in THF 20ml) was added over 20 minutes. The resulting mixture was warmed to 0°C for 30 minutes to give a solution. The solution was recooled to -78°C and then to this stirred mixture was added a solution of bromoacetonitrile (0.75 mL, 10.7 mmol) in THF (10 mL) over 25 minutes. The mixture was stirred at -78°C for 30 minutes then warmed to ambient temperature and left to stir for 21 h. After this time, the mixture was quenched with the slow addition of water (250 mL) to give a mixture with pH 14. The mixture was extracted with diethyl ether (2 x 150 mL), adding some brine to minimize emulsions. These extracts were discarded. The aqueous phase from the extraction was acidified to pH 1 with cone hydrochloric acid (approx. 1 .5 mL) and extracted with ethyl acetate (2 x 150 mL). The emulsion formed during the extraction was clarified by filtration through Celite. The organic extracts were dried (MgSC ) and evaporated in vacuo to a brown oil. The oil was purified by column chromatography over silica gel eluting with a gradient of acetone/toluene to give the title product as an off -white solid (0.36 g, 1 .6 mmol, 15%), m/z 226 (MH+). C13H23NO2 exact mass 225.17.
(ii) - 2-(2-Tert-6utoxycarbonylamino-ethyl)-undecanoic acid
Nickel chloride hexahydrate (609 mg, 2.6 mmol) was added to a stirred solution of
2-cyanomethyl - undecanoic acid (577 mg, 2.6 mmol) in methanol (50 mL) at ambient temperature to give a solution. To this solution under N2, cooled in an ice bath, was added sodium borohydride (688 mg, 18.2 mmol) in portions over 10 minutes. The black mixture was stirred at ambient temperature for 16h then filtered under suction through Celite and washed through with methanol (2 x 15mL). The filtrate and washings were evaporated to a white solid (2.6 g) which was stirred for 10 minutes with a mixture of
dichloromethane/methanol (3:1 ) (25 mL) and re-filtered. The filtrate was evaporated to give a white solid which was dried under vacuum for 1 h (1 .89 g). This solid was re-dissolved in methanol (30 ml) and to the stirred solution was added triethylamine (0.67 mL, 4.8 mmol) and then a solution of di-ferf butyl dicarbonate (590 mg, 2.7 mmol) in methanol (5 mL) and the whole mixture was stirred for 16h. After this time the mixture was evaporated and the residue re-dissolved in water (40ml) to give a solution with pH 1 1. The solution was extracted with diethyl ether (30ml) and the extract discarded. The aqueous phase was acidified to pH 4 by addition of 1 M hydrochloric acid (approx.. 9.5 mL) and extracted with ethyl acetate (2 x 30 mL) and dichloromethane (30ml). The combined extracts were dried (NazSC i) and evaporated to an oil. This material was purified by column chromatography over silica gel eluting with a gradient of diethyl ether/ iso-hexane to give the title compound as a colourless oil (309mg, 0.94 mmol, 36%), m/z 330 (MH+). Ci8H35 04 exact mass 329.26.
( S)-4-Octyl-piperazine- 1 , 3-dicarboxylic acid 1-tert-butyl ester
Figure imgf000081_0001
A solution of octanal (0.68 mL, 4.3 mmol) in tetrahydrofuran (2 mL) was added to a stirred solution of (S)-piperazine-l , 3-dicarboxylic acid 1-tert-butyl ester (1.0 g, 4.3 mmol) in tetrahydrofuran (1 15 mL). Acetic acid (0.9 mL, 15.8 mmol) was added to the solution. After stirring the reaction mixture for 30 minutes, sodium triacetoxyborohydride (1.37 g, 6.5 mmol) was added in portions over 5 minutes and the mixture stirred for 18h. The mixture was then filtered through Celite and the filtrate evaporated to an oil (1.47 g). The oil was stirred with diethyl ether (20 mL) and the insoluble solid was filtered off and purified by column chromatography over silica gel, eluting with a gradient of methanol/ethyl acetate to give the title compound as a white solid (287 mg, 0.84 mmol, 19%), m/z 343 (ΜΗ ' ). C18H34N2O4 exact mass 342.25.
Racemic trans 4-octyl-pyrrolidine- 1 , 3-dicarboxylic acid 1-tert-butyl ester
Figure imgf000081_0002
(i) - Racemic trans 1-benzyl-4-octyl-pyrrolidine-3-carboxylic acid ethyl ester
Benzyl-methoxymethyl-trimethylsilanylmethyl-amine (0.53 mL, 2.1 mmol) was added to a stirred solution of (E)-Undec-2-enoic acid ethyl ester (see J. Org. Chem., 2007, 72(17), 6628-30 for synthesis) (400 mg, 1 .9 mmol) in dry toluene (4 mL) under N2. To this stirred solution was added trifluoroacetic acid (70 pL, 0.95 mmol) and the stirred solution was heated at 50°C for 17 h under N?. After this time, the reaction mixture was poured into saturated sodium hydrogen carbonate solution (50 mL) and extracted with ethyl acetate (2 x 40 mL). The combined extracts were dried (Na?S0 ) and evaporated to an orange oil. The oil was purified by column chromatography over silica gel eluting with a gradient of diethyl ether/iso-hexane to give the title compound as a colourless oil (300 mg, 0.87 mmol, 46%), m/z 346 (MH+). C22H35NO2 exact mass 345.27. (ii) - Racemic trans 4-octyl-pyrrolidine-3-carboxylic acid ethyl ester
A suspension of 30% Pd/C (330 mg) in a solution of racemic trans 1-benzyl-4-octyl- pyrrolidine-3-carboxylic acid ethyl ester (330 mg, 1.0 mmol) in ethanol (4.9 mL) and formic acid (2.1 mL) was stirred under N2 for 22h at ambient temperature. After this time the mixture was filtered through Celite and the filtrate evaporated to a residue. This was re- dissolved in ethyl acetate (20 mL) and washed with a saturated solution of sodium hydrogen carbonate (20 mL). The latter was re-extracted with ethyl acetate (2 x 20mL) and the combined extracts were dried ( a2S04) and evaporated to a give the title compound as a colourless oil (174 mg, 0.68 mmol, 68%), m/z 256 (MH+). C15H29NO2 exact mass 255.22.
(iii) - Racemic trans 4-octyl-pyrrolidine-1.3-dicarboxylic acid 1-tert-butyl ester 3-ethyl ester
Triethylamine (1 14 L, 0.82 mmol) and a solution of di-teri butyl dicarbonate (178 mg, 0.82 mmol) in dichloromethane (2 mL), were successively added to a stirred solution of racemic trans 4-octyl-pyrrolidine-3-carboxylic acid ethyl ester (174 mg, 0.68 mmol) in dichloromethane (8 mL). After stirring the solution for 20h it was diluted with diethyl ether (20 mL) and the solution washed with saturated ammonium chloride solution (30 mL). The latter was re-extracted with diethyl ether (20ml) and the combined extracts dried (Na2SC>4) and evaporated to a colourless oil. The oil was purified by column chromatography over silica gel eluting with a gradient of ethyl acetate/iso-hexane to afford the title compound as an oil (196 mg, 0.55 mmol, 81 %), m/z 356 (MH+). C20H37NO4 exact mass 355.27.
(iv) - Racemic trans 4-octy l-pyrrol id i n e- 1 , 3-d ica rboxy I ic acid 1 -tert-butyl ester A solution of lithium hydroxide monohydrate (81 mg, 1 .9 mmol) in water (1 .5 mL) was added to a stirred solution of racemic trans 4-octyl-pyrrolidine-1 ,3-dicarboxylic acid 1-tert-butyl ester 3-ethyl ester (228 mg, 0.64 mmol) in methanol (6 mL) at ambient temperature. The solution was stirred for 17 h, then diluted with water (20 mL) and adjusted to pH 2 with 1 M hydrochloric acid (1.85 mL). The resulting milky mixture was extracted with ethyl acetate (3 x 15 mL) and the combined extracts were dried (Na2SO.() and evaporated to give the title compound as a colourless oil (193 mg, 0.59 mmol, 92%), m/z 328 (MH *). C18H33 O4 requires 327.24. Tert-butoxycarbonyl-3-aminomethyl undecanoic acid
Figure imgf000083_0001
(i) - 3-Nitromethyl undecanoic acid ethyl ester
To a solution of (E)-Undec-2-enoic acid ethyl ester (1.46 g, 6.8 mmol) in acetonitrile (5.84 mL) were added nitromethane (1.86 mL, 34.3 mmol) and DBU (1 .05 mL, 7.0 mmol) at room temperature. The reaction mixture was heated at 65 C for 4h, cooled and concentrated. The residue was partitioned between ethyl acetate (20 mL) and water (20 mL). The aqueous layer was extracted twice with ethyl acetate (20 mL). The combined organic extracts were washed further with 0.1 M HCI (30 mL), water (30 mL) and brine (30 mL). The organic extract was dried over magnesium sulphate, filtered and concentrated. The crude material was purified by automated flash column chromatography eluting with 0-80% ethyl acetate in hexane. Fractions were isolated and concentrated to leave a colourless oil. Yield 0.48 g, 26%. 1H NMR (400 MHz, CDCb) δ (ppm): 0.82 (t, 3H, CH3), 1 .25 (m, 16H, CH2), 1.42 (m, 3H, CH3), 2.42 (m, 2H, CH2), 2.62 (m, 1 H, CH), 4.19 (m, 2H, CH2), 4.46 (m, 2H, CH2).
(ii) - 3-Aminomethyl undecanoic acid ethyl ester
To a solution of 3-nitromethyl undecanoic acid ethyl ester (200 mg, 0.73 mmol) in acetic acid (5 mL) were added at room temperature THF (10.52 mL), water (2.1 mL), concentrated HCI (820 uL), and portionwise Zn dust (600 mg, 9.2 mmol). The reaction mixture was vigorously stirred for 2.5 h. The suspension was then filtered and the filtrate was concentrated in vacuo. The residue was diluted with DCM (20 mL) washed with water (20 mL). The organic layer was isolated and dried over magnesium sulphate, filtered and the filtrate was concentrated in vacuo to leave the acetate salt. Yield 150 mg, 88%. m/z 244.2 (MH+).
C14H29N02 requires 243.22. (iii) - Tert-butoxycarbonyl-3-aminomethyl undecanoic acid ethyl ester
To a solution of 3-aminomethyl undecanoic acid ethyl ester (150 mg, 0.6 mmol) in THF (20 mL), triethyl amine (170 L, 1.2 mmol) was added. After 10 min di-iert-butyl dicarbonate (147 mg, 0.67 mmol) was added and the reaction mixture was stirred for 6 h at room temperature. The reaction mixture was evaporated to dryness; the crude material was re- dissolved in water (20 mL) and extracted with DCM (20 mL). The organic layer was isolated, dried over magnesium sulphate, filtered and concentrated in vacuo. The crude material was purified by automated flash column chromatography eluting with 0-80% ethyl acetate in hexane. Fractions were isolated and evaporated to leave a colourless oil. Yield 70 mg, 33%. m/z (MH+). C19H37N042 requires 343.27.
(iv) - Tert-butoxycarbonyl-3-aminomethyl undecanoic acid
Tert-butoxycarbonyl-3-Aminomethyl undecanoic acid ethyl ester (70mg, 0.2 mmol) was dissolved in THF (600 μΙ_). To the solution was added 1 M NaOH (4 mL) and the reaction was stirred at room temperature for 16 h. The reaction mixture was then concentrated, re- dissolved in water (20 mL) and extracted with DCM (20 mL). The aqueous layer was isolated, acidified to pH 1 using 1 M HCI and extracted with DCM (20 mL). The organic layer was isolated, dried over magnesium sulphate, filtered and concentrated to dryness to leave a yellow oil. Yield 40 mg, 63%.m/z 316.63 (ΜΗ '). C17H33N04 requires 315.24.
(S)-4-lsobutyl-piperazine-1 ,3-dicarboxylic acid 1-tert-butyl ester
Figure imgf000084_0001
The title compound was prepared in 43% yield from iso-butyraldehyde and (S)-piperazine- 1.3-dicarboxylic acid 1-tert-butyl ester using the method described for S)-4-Octyl-piperazine- 1 ,3-dicarboxylic acid 1 -tert-butyl ester, m/z 287 (ΜΗ '), C14H26 2O4 requires 286.19. Racemic trans-4-isobutyl-pyrrolidine-1 3-dicarboxylic acid 1-tert-butyl ester
Figure imgf000084_0002
The title compound was prepared from (E)-5-methyl-hex-2-enoic acid ethyl ester (see Synthesis 2009, 15, 2634-45 for a preparation) by an analogous sequence of reactions to that described for Racemic trans 4-octyl-pyrrolidine-1 ,3-dicarboxylic acid 1-tert-butyl ester. For the title compound m/z 272 (ΜΗ'), C14H25NO4 requires 271 .18. 1-Tert-butoxycarbonyl-4-octyl-piperidine- -carboxylic acid
Figure imgf000085_0001
(i) - 1 -Tert-butyl 5-ethyl 4-oct-1 -ynyl-3.6-dihydro-2H-pyridine-1 ,5-dicarboxylate
Figure imgf000085_0002
To a solution of 1 -tert-butyl 5-ethyl 4-(trifluoromethylsulfonyloxy)-3.6-dihydro-2H-pyridine- 1 ,5-dicarboxylate (US 201 1/0190278) (620 mg, 1 .53 mmol) in ethyl acetate (15 mL) was added 1-octyne (340 μΙ_, 2.31 mmol), triethylamine (320 μΙ_, 2.30 mmol),
bis(triphenylphosphine)palladium (II) dichloride (54 mg, 0.077 mmol) and copper iodide (3 mg, 0.015 mmol). The reaction mixture was stirred at 50°C for 4 hours, then filtered under suction through Celite and washed through with ethyl acetate. The filtrate was evaporated at reduced pressure. The residue was purified by silica gel chromatography eluting with 0 - 30% ethyl acetate in iso-hexane to yield the title compound (364 mg, 66%). m/z 364 (MH+), C21 H33N04 exact mass 363.241. (ii) - 1 -Tert-butyl 3-ethyl 4-octylpiperidi late
Figure imgf000085_0003
To a solution of 1 -tert-butyl 5-ethyl 4-oct-1-ynyl-3,6-dihydro-2H-pyridine-1.5-dicarboxylate (360 mg, 0.99 mmol) in acetic acid (25 mL) was added platinum oxide (40 mg). The reaction mixture was hydrogenated for 16 hours and then a further quantity of platinum oxide (50 mg) was added and hydrogenated for a further 4 hours. The reaction mixture was then filtered under suction through Celite and washed through with ethyl acetate. The filtrate was evaporated at reduced pressure and then the residue was partitioned between ethyl acetate and water. The pH of the aqueous layer was adjusted to pH 10 by the addition of 880 ammonia. After separation of the layers, the aqueous phase was re-extracted with ethyl acetate and then the combined organic layers were passed through a hydrophobic frit. The solvent was evaporated at reduced pressure and the residue purified by silica gel chromatography eluting with 0 - 30% ethyl acetate in iso-hexane to yield the title compound {relative stereochemistry, presumed cis} (133mg, 36%). m/z 370 (MH+), C21 H39N04 exact mass 369.288.
(iii) - 1-Tert-butoxycarbonyl-4-octyl-piperidine-3-carboxylic acid
To a solution of 01 -tert-butyl 03-ethyl 4-octylpiperidine-1.3-dicarboxylate (1 10 mg,
0.30mmol) in tetrahydrofuran (2 mL) and methanol (2 mL) was added 2 M sodium hydroxide solution (2 mL). The reaction mixture was stirred at room temperature for 6 hours and then concentrated at reduced pressure. The residue was partitioned between ethyl acetate and water and the pH adjusted to 2 by the addition of 1 M hydrochloric acid. After separation of the layers, the organic phase as washed with water, dried over magnesium sulphate, filtered and concentrated to give the title compound (102 mg, 100%). m/z 342 (MH+), C19H35N04 exact mass 341 .257.
Racemic trans- 1-(tert-butoxycarbonyl)-5-isobutylpiperidine-3-carboxylic acid
Figure imgf000086_0001
(i) - 5-lsobutyl-nicotinic acid ethyl ester
Isobutylmagnesium chloride (2 M solution in THF) (9.25 mL, 18.52 mmol) was added dropwise to a solution of zinc bromide (4.17 g, 18.52 mmol) in THF (30 mL) at 0°C under N2 and the resulting suspension was stirred for 30 minutes. The mixture was cooled to -78°C and [1 , 1 '-Bis(diphenylphosphino)ferrocene]dichloropalladium(ll), complex with
dichloromethane (252 mg, 0.309 mmol) was added followed by a solution of the 5-bromo- nicotinic acid ethyl ester (1.42 g, 6.17 mmol) in THF (5 mL). After 5 minutes the reaction was allowed to warm to room temperature and stirring was continued for 3 hours. The reaction mixture was diluted with water and ethyl acetate and the phases were separated. The aqueous layer was extracted with ethyl acetate and the combined organic layers were dried (MgSO.i) and the solvent evaporated to afford a crude oil. This was purified by Biotage SP4, 50 g SNAP cartridge eluting with 0 to 50% EtOAc / i-hexane to afford the 5-iosbutyl- nicotinic acid isobutyl ester (365 mg) followed by the 5-isobutyl-nicotinic acid ethyl ester
(576mg).
5-isobutyl-nicotinic acid isobutyl ester: 1H NMR (CDCb) 9.10 (1 H, s), 8.60 (1 H, s), 8.10 (1 H, s), 4.15 (2H, d), 2.55 (2H, d), 2.10 (1 H, sept), 1.95 (1 H, sept), 1.05 (6H, d), 0.95 (6H, d). 5-isobutyl-nictinic acid ethyl ester: H NMR (CDCb) 9.05 (1 H, s), 8.55 (1 H, s), 8.10 (1 H, s), 4.45 (2H, q), 2.55 (2H, d), 1.90 (1 H, sept), 1 .45 (3H, t), 0.95 (6H, d).
(ii) - Racemic trans-1-(tert-butoxycarbonyl)-5-isobutylpiperidine-3-carboxylic acid The title compound was prepared from 5-isobutyl-nicotinic acid ethyl ester under the same conditions as described for frans-1 -(iert-butoxycarbonyl)-5-octyl 3-carboxylic acid, m/z (ES") 284 (M-H). C15H27N04 requires: 285.19.
The trans geometry of the compound was confirmed from NMR analysis of the deprotected form of the title compound.
1-tert-Butoxycarbonyl-5-isobutoxy-piperidine-3-carboxylic acid
Figure imgf000087_0001
(i) - Methyl 5-isobutoxypyridine-3-carboxylate
To a solution of methyl 5-hydroxynicotinate (1.5 g, 9.80mmol) in dimethylformamide (20 ml) was added potassium carbonate (2.7 g, 19.6 mmol) and 1 -bromo-2-methylpropane (1 .2 ml_, 1 1 .0 mmol). The reaction mixture was stirred at 80°C for 5 hours and then allowed to cool to room temperature. The mixture was concentrated at reduced pressure and the residue partitioned between ethyl acetate and water. After separation of the layers, the aqueous phase was re-extracted with ethyl acetate. The combined organic layers were dried over magnesium sulphate, filtered and the solvent evaporated at reduced pressure. The residue was purified by silica gel chromatography eluting with 0 - 100% ethyl acetate in iso-hexane to yield the title compound (1.29g, 63%). m/z 210 (MH+), C11 H 15NO3 exact mass 209.105.
(ii) - Methyl 5-isobutoxypiperidine-3-carboxylate To a solution of methyl 5-isobutoxypyridine-3-carboxylate (1.5 g, 7.18 mmol) in acetic acid (50 ml_) was added platinum oxide (100 mg). The reaction mixture was hydrogenated for 3 days and then a further quantity of platinum oxide (50 mg) was added and the mixture hydrogenated for a further 5 hours. The reaction mixture was then filtered under suction through Celite and washed through with ethyl acetate. The filtrate was evaporated at reduced pressure and then the residue was partitioned between ethyl acetate and water. The pH of the aqueous layer was adjusted to pH 10 by the addition of .880 ammonia. After separation of the layers, the aqueous phase was re-extracted with ethyl acetate and then the combined organic layers were dried over magnesium sulphate and then filtered. The solvent was evaporated at reduced pressure to yield the crude title compound (961 mg). m/z 216 (MH+), C H2iN03 exact mass 215.152. (iii) l-(tert-butyl) 3-methyl 5-isobutoxypiperidine-1 ,3-dicarboxylate
To a solution of methyl 5-isobutoxypiperidine-3-carboxylate (960 mg, 4.49 mmol) in dichloromethane (50 mL) was added di-fert-butyl dicarbonate (1 .1 g, 5.04 mmol). The reaction mixture was stirred at room temperature for 16 hours and then concentrated at reduced pressure. The residue was purified by silica gel chromatography eluting with 0 - 100% diethyl ether in iso-hexane to yield the title compound (665mg, 47%). m/z 260 (MH+- tBu), C12H21 NO5 exact mass 259.142.
(iv) - 1 -tert-butoxycarbonyl-5-isobutoxy-piperidine-3-carboxylic acid
To a solution of l-(tert-butyl) 3-methyl 5-isobutoxypiperidine-1 ,3-dicarboxylate (660 mg, 2.1 mmol) in dioxane (5 mL) and water (2.5 mL) was added lithium hydroxide monohydrate (266 mg, 6.33 mmol). The reaction mixture was stirred at room temperature for 16 hours and then partially concentrated at reduced pressure. The residue was partitioned between ethyl acetate and water and the pH of the aqueous layer adjusted to pH 1 by the addition of 1 M hydrochloric acid. After separation of the layers, the aqueous phase was re-extracted with ethyl acetate. The combined organic layers were dried over magnesium sulphate, filtered and concentrated to yield the title compound (348mg, 55%). m/z 302 (ΜΗ ' ), C15H27NO5 exact mass 301.189.
(3RS, 5SR)- 1-(tert-butoxycarbonyl)-5-(isobutylcarbamoyl) piperidine-3-carboxylic acid
Figure imgf000088_0001
To a solution of 2, 4-dioxo-3-oxa-7-aza-bicyclo[3.3.1] nonane-7-carboxylic acid tert-butyl ester (for a synthesis see US2008/0319018 A1 ), (70 mg, 0.27 mmol) in THF (5 mL) was added isobutylamine (27 pL, 0.27 mmol). The reaction mixture was left to stir at rt 18 h. reaction mixture was then evaporated to dryness to leave a pale yellow solid (yield 90 mg, quantitative) m/z 329.0 (MH+), C16H28N205 requires 328.20.
(S)-4-((Tert-butoxycarbonyi)amino-2-(((S)-6-methyloctyl)amino)butanoic acid
Figure imgf000089_0001
(i) (S)-6 methyloctanal Under nitrogen gas atmosphere, (S)-(+)-6-methyl-1 -octanol (197 mg, 1 .36 mmol) [TCI Ltd] in DCM (3 mL) was added to 0.3M Dess Martin periodinane solution (5 mL, 1.5 mmol) dropwise at room temperature. The reaction mixture was stirred for 1.5h at ambient temperature. The reaction mixture was evaporated and re-suspended in ether (50 mL) and filtered. The filtrate was evaporated to leave a colourless oil. The oil was purified by column chromatography over silica gel, eluting with a gradient of hexane/ethyl acetate to give the title compound as a colourless oil (80 mg, 41 %).
(ii) Methyl (S)-4-(fert-butoxycarbonyl)amino)-2-((S)-6-methyloctyl)amino) butanoate (S)-6 methyloctanal was reacted with methyl (S)-4-(£erf-butoxycarbonyl)amino)-2- aminobutanoate using the reductive alkylation method as described for (S)-4-octyl- piperazine-1.3-dicarboxylic acid 1 -tert butyl ester. The title compound was obtained as a white solid (80 mg, 42%), m/z 359.2 (ΜΗ '). C19H38N2O4 exact mass 358.28.
(S)-4-((tert-butoxycarbonyl)amino-2-((S)-6-methyloctyl)amino)butanoic acid
To a solution of methyl (S)-4-(teri-butoxycarbonyl)amino)-2-((S)-6-methyloctyl)amino) butanoate (80 mg, 0.22 mmol) in methanol (5 mL) was added lithium hydroxide (1 1 mg, 0.44mmol) in water (1 mL). The reaction mixture was stirred at room temperature for 16 hours. The reaction mixture was concentrated at reduced pressure and the residue was partitioned between ethyl acetate and water. The aqueous phase was acidified by the addition of 1 M hydrochloric acid and the product was extracted into ethyl acetate. The organic phase was dried over magnesium sulphate, filtered and the filtrate was evaporated at reduced pressure to yield the title compound (50 mg, 66%), m/z 345.2 (MH+), C18H36 2O4 exact mass 344.27.
4-((fert-Butoxycarbonyl)amino)-2-cyclohexylbutanoic acid
Figure imgf000090_0001
A suspension of platinum oxide (80 mg, 0.28 mmol) in acetic acid (2 mL) was added to a stirred solution of 4-Boc-amino-2-phenyl-butyric acid (300 mg, 1 .07 mmol) in acetic acid (20 mL). The reaction was hydrogenated for 24h at ambient temperature and atmospheric pressure. The reaction mixture was filtered through Celite and washed with acetic acid (20 mL). The filtrate was evaporated at reduced pressure to leave a yellow oil (300 mg, 98%). m/z 285.9(M '), C15H27NO4 exact mass 285.19.
2-[(fert-Butoxycarbonylamino)methyl]octanoic acid
Figure imgf000090_0002
(i) Ethyl 2-cyanooctanoate
Figure imgf000091_0001
A mixture of ethyl cyanoacetate (2 mL, 19.0 mmol), 1-iodohexane (3.0 ml_, 20.0 mmol) and potassium carbonate (2.76 g, 20.0 mmol) in acetone (100 mL) was heated to reflux for 4 h. After cooling to room temperature, the reaction mixture was filtered through Celite and washed with acetone. The filtrate was evaporated at reduced pressure and then partitioned between dichloromethane and saturated ammonium chloride solution. After separation of the layers, the organic phase was washed with brine, dried over magnesium sulphate, filtered and concentrated at reduced pressure. The product was purified by silica gel chromatography eluting with 0 - 30% ethyl acetate in /so-hexane to yield the title compound as a colourless oil (2.29 g, 61 %). m/z 198 (ΜΗ ' ), CnH19N02 exact mass 197.14. (ii) Ethyl 2-(aminomethyl)octanoate
Figure imgf000091_0002
To a solution of ethyl 2-cyanooctanoate (880 mg, 4.47 mmol) in methanol (40 mL) was added cobalt chloride (1 .14 g, 8.76 mmol). The mixture was cooled to 0°C and then treated portion-wise with sodium borohydride (1.67 g, 44 mmol). After the addition was complete, the reaction mixture was warmed to room temperature and stirred for a further 30 minutes.
The mixture was quenched with 1 M hydrochloric acid and stirred for 2 minutes. The mixture was then basified to ~ pH 1 1 by the addition of .880 ammonia and the product extracted into dichloromethane (* 4). The combined organic phases were dried over magnesium sulphate, filtered and concentrated to give the crude title compound as a pale brown oil (775 mg,
86%). m/z 202 (MH+), C11 H23NO2 exact mass 201.17. (iii) Ethyl 2-[(iert-butoxycarbonylamino)methyl]octanoate
Figure imgf000092_0001
To a solution of ethyl 2-(aminomethyl)octanoate (775 mg, 3.86 mmol) in dichloromethane (50 ml) was added di-tert-butyl dicarbonate (1 .0 g, 4.58mmol). The reaction mixture was stirred at room temperature for 16h and then concentrated at reduced pressure. The product was purified by silica gel chromatography eluting with 0 - 20% ethyl acetate in iso- hexane to yield the title compound as a colourless oil (818 mg, 71 %). m/z 246 (M-BOC) ', C16H31 NO4 exact mass 301.22.
(iv) 2-[(fert-Butoxycarbonylamino)methyl]octanoic acid
Figure imgf000092_0002
To a solution of ethyl 2-[(tert-butoxycarbonylamino)methyl]octanoate (816 mg, 2.71 mmol) in dioxane (12 ml_) and water (6 mL) was added lithium hydroxide (350 mg, 8.33 mmol). The reaction mixture was stirred at room temperature for 16 h and then partially concentrated at reduced pressure. The residue was partitioned between diethyl ether and water and the pH adjusted to 1 by the addition of 1 M hydrochloric acid. After separation of the layers, the aqueous phase was re-extracted with diethyl ether (x 2). The combined organic layers were dried over magnesium sulphate, filtered and concentrated to give a colourless oil (715 mg, 97%). m/z 272 (M-H) -, C14H27NO4 exact mass 273.19.
Synthesis Examples
Table 4A includes examples of the invention. All compounds were isolated as TFA salts unless otherwise specified. Compounds D9, D1 1 , D15 and D25 were also prepared as acetate salts according to the general method described herein. The structures in the table depict the N-terminal group (-R) and side chain on the Polymyxin B hepta peptide scaffold (PMBH, below). Relative stereochemistry is depicted by heavy or dashed lines. Absolute stereochemistry is depicted by heavy or hashed wedged bonds. The PMBH scaffold:
Figure imgf000093_0001
Table 4A - Example Compounds
Figure imgf000094_0001
Figure imgf000095_0001
Figure imgf000096_0001
Figure imgf000097_0001
Figure imgf000098_0001
Figure imgf000099_0001
Figure imgf000100_0001
Figure imgf000101_0001
Figure imgf000102_0001
Figure imgf000103_0001
Figure imgf000104_0001
The comparator compounds were Polymyxin B (PMB), C1 (NAB-739), and C2 (CB-182,804).
CB-182,804 (C2) is a polymyxin decapeptide derivative with an aryl urea substituent at the N-terminus, which has been claimed to have lower toxicity than Polymyxin B (shown as compound 5 in WO 2010/075416), and was prepared by the present inventors. C1 was also prepared in- house, and corresponds to NAB-739 (as described by Vaara in, for example, WO 2008/01773. Other comparator compounds were prepared in-house as shown in Table 4B.
Table 4B - Further Comparator Compounds
Figure imgf000105_0001
Figure imgf000106_0001
Further Synthesis Examples
Table 4C includes additional compounds of the invention. All compounds were prepared using general method 2A, as described above, apart from example D93 which used dicyclohexyl carbodiimide in the final coupling step. All compounds were isolated as TFA salts. Compounds D65, D67, D69, D76, D77, D78, D81 and D86 were also prepared as acetate salts.
Structures depict the N-terminal group and side chain on the Polymyxin B or Polymyxin E hepta peptide scaffold (PMBH or PMEH, below). Relative stereochemistry is depicted by heavy or dashed lines. Absolute stereochemistry is depicted by heavy or hashed wedged bonds.
In Table 4C, Scaffold refers to polymyxin B ("B") and polymyxin E ("E") scaffolds, as shown below. R- is the N-terminal and side-chain on the heptapeptide.
Similarly, in Table 4D, Scaffold refers to polymyxin B ("B") and polymyxin E ("E") scaffolds, as shown below. R- is the N-terminal and side-chain on the heptapeptide.
Figure imgf000107_0001
Polymyxin B heptapeptide scaffold (PMBH) Polymyxin E heptapeptide scaffold (PMEH)
Table 4D: All compounds were isolated as TFA salts. Compounds D95, D100, D101 , D102, D103, D104, D105, D106, D107, and D1 14 were also prepared as acetate salts. Table 4C - Further Example Compounds
Figure imgf000108_0001
Figure imgf000109_0001
Figure imgf000110_0001
Figure imgf000111_0001
Figure imgf000112_0001
Figure imgf000113_0001
Figure imgf000114_0001
Figure imgf000115_0001
Figure imgf000116_0001
Figure imgf000117_0001
Figure imgf000118_0001
Figure imgf000119_0001
Figure imgf000120_0001
Figure imgf000121_0001
Table 4D - Additional Further Example Compounds
Figure imgf000122_0001
Figure imgf000123_0001
Figure imgf000124_0001
Figure imgf000125_0001
Figure imgf000126_0001
Figure imgf000127_0001
Biological Activity
To evaluate the potency and spectrum of the compounds both alone and in combination with another agent, susceptibility testing was performed against at least two strains of each of the four gram negative pathogens, Escherichia coll, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii.
MIC Determination The inoculum was prepared by making a direct suspension of isolated colonies (selected from an 18-24 hour Mueller-Hinton agar plate) adjusted to the 0.5 McFarland standard. MIC testing was performed by two-fold serial antibiotic dilutions in cation-adjusted Mueller- Hinton Broth in sterile 96-well microtitre plates in a total volume of 170 μΙ_ (150 μΙ_ broth containing the antimicrobial agent, 20 μΙ_ inoculum). The assays were performed in duplicate. Plates were incubated aerobically without shaking for 18-20 hours at 35 C with the MIC defined as the lowest concentration of drug that prevented visible growth.
In cases where the duplicate values varied by less than 2-fold, the lower of the two values is reported. If a variation of greater than 2 -fold was observed, the assay was considered non-valid. Several of the compounds were subjected to multiple tests, and where this is the case, the MIC reflects the modal value obtained.
Combination Activity
Table 5C below shows the activity, shown by way of MIC values, of Example Compounds in the presence of Rifampicin. MIC values were determined against E. coli and K. pneumoniae in the presence of a fixed concentration (2 g/mL) of Rifampicin, and against A. baumannii in the presence of 0.25 g/mL of rifampicin for the example compounds and the comparator compounds C1 and C2 and CC3. CB-182.804 (C2) is a polymyxin decapeptide derivative with an aryl urea substituent at the N-terminus, which has been claimed to have lower toxicity than Polymyxin B (shown as compound 5 in WO 2010/075416), and was prepared by the present inventors. C1 was also prepared in-house, and corresponds to NAB-739 (as described by Vaara in, for example, WO 2008/017734). CC3 corresponds to compound 5x in Magee et al., J. Med. Chem. 2013, 56, 5079. Table 5C - MIC Values (micrograms/mL) for Example Compounds in combination with Rifampicin (2 pg/mL or 0.25 pg/mL).
Figure imgf000129_0001
Table 5D shows the MIC values for Further Example Compounds in the presence of Rifampicin. MIC values were determined against E. coli and K. pneumoniae in the presence of a fixed concentration (2 pg/mL) of Rifampicin, and against A. baumannii in the presence of 0.25 pg/mL of rifampicin.
Table 5D - MIC Values (micrograms/mL) for Further Example Compounds in combination with Rifampicin (2 pg/mL or 0.25 pg/mL).
E. coli K. pneumoniae A. baumannii
ATCC
NCTC ATCC ATCC NCTC ATCC
Example BAA- 13441 25922 4352 13424 BAA-747
2146
D2 0.03 <0.015 0.125 0.03 <0.015 0.03
D5 0.06 0.03 0.25 0.03 <0.015 0.25
D6 0.03 <0.015 0.06 ND <0.015 0.06
D7 0.5 0.06 0.5 0.125 0.03 1
D8 ND <0.015 0.06 0.03 <0.015 0.03
D9 0.06 <0.015 0.06 0.03 0.03 <0.015
D10 0.5 ND 0.25 0.125 <0.015 0.5
D1 1 0.06 0.125 0.5 0.125 0.25 0.125
D12 0.25 0.06 0.25 0.125 0.03 0.5
D13 0.125 0.06 0.125 0.125 0.06 0.125
D15 0.03 <0.015 0.125 <0.015 <0.015 <0.015 E. coli K. pneumoniae A. baumannii
ATCC
NCTC ATCC ATCC NCTC ATCC
Example BAA-
13441 25922 4352 13424 BAA-747
2146
D25 0.03 <0.015 0.06 <0.015 ND <0.015
D26 1 0.25 4 0.5 1 2
D27 ND 0.125 4 0.5 1 1
D28 0.5 1 2 0.5 1 1
D29 <0.015 <0.015 0.125 0.03 0.06 0.03
Table 5E shows the MIC values (micrograms/mL) recorded for Further Examples (D50 and D65) and polymyxin each tested in a 1 :1 (wt:wt) combination with Rifampicin.
Table 5E - MIC values (microgram/mL) for test compounds in 1 :1 combination with rifampicin
Figure imgf000130_0001
MIC values (microgram/mL) refer to the total drug concentration (i.e. test agent plus
Rifampicin).
In Vitro Renal Cell Toxicity Assay
The renal cell toxicity of the compounds was assessed in an in vitro assay using the HK-2 cell line, an immortalized proximal tubule cell line derived from a normal human kidney. The endpoint to describe the toxicity of the compounds was the reduction of resazurin correlating with the metabolic activity of the cells. Cells were cultured in 150 cm2 flasks in 25 ml_ supplemented KSF (with 5 ng/mL EGF and 50 pg/mL BPE). Cells were maintained at 70% confluence with a maximum of 25 passages.
Day 1 : Media was removed and cells were washed with 10ml DPBS. Six ml of a 0.25% trypsin solution with EDTA was then added to the flask and the cells returned to the incubator. After 1 to 2 minutes incubation, 14 mL media was added to the flask to inactivate the trypsin. The cell suspension was transferred to a centrifuge tube and the cells pelleted at 1000 rpm for 6 minutes. The cell pellet was then resuspended in fresh media supplemented with EGF and BPE. The cell number was counted and cells were diluted to 46875 cells/mL in fresh medium supplemented with epidermal growth factor (EGF) and bovine pituitary extract (BPE). . 7500 cells were dispensed in each well in a volume of 160μΙ and incubated at 37 C for 24 h.
Day 2: Test compounds were prepared directly into the media, or from stock solutions to result in no more than 0.5% DMSO, or 5% water in the final assay. Nine point
concentrations were prepared from 1000 pg/mL to 1.95 pg/mL in two-fold dilutions in fresh medium. The microtiter plates were removed from the incubator and the media replaced with 100 pL of the dilutions of the compound solution. Every set of concentration was done in triplicate, and positive and negative controls were added to each plate. The plates were then incubated for 24h at 37 C with 5% CO2 in a humidified atmosphere.
Day 3: The reagent containing the resazurin (CellTiter-Blue, Promega) was diluted in PBS (1 :4) and added at 20% (v/v) to each well. The plates were then incubated at 37 C for 2h before the fluorescent reduction product was detected.
Media only background values were subtracted before the data was analysed using GraphPad Prism. Compound concentration values were plotted as log values to enable a dose-response curve to be fitted and ICso values determined.
The data is shown in Table 6, expressed relative to polymyxin B.
Sole Activity
Table 6B below shows the activity, shown by way of MIC values, of Example Compounds in the absence of a second agent together with the toxicity against the HK-2 cell line
(measured in relation to IC50 values and expressed relative to the value for polymyxin B) MICs were determined as described herein. HK-2 cell I C50 values were determined as described herein. Values are reported relative to Polymyxin B.
The MIC values were compared to compounds known from the literature. The data is in table 6B. C2 (CB-182.804) is a polymyxin decapeptide derivative described by Cubist (shown as compound 5 in WO 2010/075416), C1 is NAB-739 (as described by Vaara in, for example, WO 2008/01773). CC3 corresponds to Compound 5x Magee et al, J. Med. Chem., 2013, 56, 5079.
Table 6B - MIC Values (micrograms/mL) and HK-2 cell toxicity for Example Compounds (measured in relation to IC50 values and expressed relative to the value for polymyxin B) E. coii K. pneumoniae P. aeruginosa A. baumannii
HK-2
Ex. ATCC ATCC
NCTC ATCC ATCC CCUG ATCC NCTC ICso rei
BAA- BAA- 4352 59347 to PMB 13441 25922 27853 13424
2146 747
PMB 0.25 0.25 0.5 0.25 0.5 0.5 0.5 0.25 1
C1 1 2 2 ND >8 8 2 ND 17
C2 2 1 2 1 1 0.5 0.5 0.5 2
CC3 1 2 ND 0.5 1 1 1 0.5 17
D1 4 4 1 2 2 0.5 4 4 5.7
D2 0.5 1 0.25 ND 0.5 0.25 1 2 7.6
D3 0.5 0.25 2 1 1 0.5 >8 >8 ND
D4 1 0.5 ND ND 0.5 0.25 2 4 7.5
D5 >8 8 >8 8 >8 1 >8 >8 15.3
D6 0.25 0.25 0.5 0.25 0.5 0.25 1 1 3.7
D7 >8 >8 >8 8 >8 2 >8 >8 ND
D8 0.25 0.125 0.5 0.125 1 0.5 0.5 0.25 ND
D9 0.25 0.25 0.5 0.25 1 0.25 0.5 1 1 1.7
D10 4 4 >8 8 2 1 8 >8 4.4
D1 1 0.25 0.25 0.25 0.25 0.5 0.5 0.5 1 2.5
D12 >8 >8 >8 >8 4 1 >8 >8 ND
0.25,
D13 0.125 0.25 0.125 0.5 0.5 0.125 0.5 4.1
1
D14 >8 >8 >8 >8 4 1 >8 >8 ND
D15 0.5 0.25 ND ND 0.5 0.25 2 2 17
D16 >8 >8 >8 >8 1 8 >8 >8 ND
D17 2 2 2 2 0.5 0.5 4 2 ND
D18 4 4 >8 8 2 4 >8 >8 ND
D19 2 2 4 2 1 0.5 ND 2 ND E. coii K. pneumoniae P. aeruginosa A. baumannii
HK-2
Ex. ATCC ATCC
NCTC ATCC ATCC CCUG ATCC NCTC ICso rei
BAA- BAA- 4 to PMB 13441 25922 4352 59347 27853 1342
2146 747
D20 4 4 >8 8 1 0.5 >8 >8 ND
D21 0.5 0.5 1 0.25 0.5 0.5 2 0.5 ND
D22 4 4 >8 ND 1 2 >8 >8 ND
D23 1 ND 1 ND 0.5 0.5 0.25 0.25 0.8
D24 >8 >8 >8 >8 >8 1 >8 >8 ND
D25 0.5 0.25 0.5 0.25 0.5 0.25 1 0.5 8
D26 2 0.5 2 1 0.5 0.5 2 0.5 ND
D27 0.06 0.125 0.5 0.25 0.5 0.5 1 0.25 1
D28 0.125 0.125 0.5 0.25 0.5 1 0.25 1 .3
D29 1 1 0.5 0.5 0.5 0.5 0.5 ND
D30 2 2 ND 1 1 2 1 ND
D31 1 2 ND 0.5 1 0.5 2 1 1 .8
D32 1 1 ND 1 0.5 1 2 ND
D33 2 1 ND 2 0.5 2 1 ND
D34 1 1 2 2 1 2 2 ND
D35 1 1 2 2 1 1 2 ND
D36 0.25 0.06 ND 0.25 0.25 0.25 0.5 4.5
D37 2 0.5 1 0.5 0.5 1 1 ND
D38 8 8 8 4 1 2 >8 6.3
D39 0.5 0.125 0.25 0.125 0.25 0.25 0.5 5.4
D40 2 2 4 2 0.5 8 >8 ND
D41 1 1 ND 2 0.5 1 2 ND
D42 0.25 0.25 0.5 0.125 0.5 0.25 0.5 0.25 6.6 E. coii K. pneumoniae P. aeruginosa A. baumannii
HK-2
Ex. ATCC ATCC
NCTC ATCC ATCC CCUG ATCC NCTC ICso rei
BAA- BAA- 4352 59347 to PMB 13441 25922 27853 13424
2146 747
D43 4 2 4 2 2 1 4 4 ND
D44 0.5 1 0.5 ND 0.5 0.25 ND 0.25 1 .3
D45 2 0.5 2 0.5 4 1 4 8 ND
D46 1 1 1 0.5 1 0.5 2 1 ND
D47 8 4 8 4 >8 2 >8 >8 ND
D48 0.125 0.125 0.25 0.125 1 0.25 0.5 0.5 ND
D49 8 8 8 4 4 2 >8 >8 ND
D50 0.06 0.06 0.125 0.06 1 0.5 0.25 0.25 7.4
D51 0.5 0.5 0.5 0.125 1 0.5 1 1 34
D52 0.125 0.125 0.25 0.125 0.5 0.5 0.25 0.5 ND
Further Sole Activity The Further Synthesis Examples were tested against a range of Gram negative bacteria, and tested for HK-2 cell toxicity. The data is contained in Table 6C. All the worked examples, including the Synthesis and Further Synthesis Examples, were also tested against a range of Gram negative bacteria that are resistant to Polymyxin B (i.e. those strains where Polymyxin B has an elevated MIC value). The data is contained in Table 6D.
In the tables ND is not determined. Table 6C - MIC Values (micrograms/mL) and HK-2 cell toxicity (measured in relation to I C50 values and expressed relative to the value for polymyxin B) for additional Example
Compounds.
Figure imgf000135_0001
E. coii K. pneumoniae P. aeruginosa A. baumannii HK-2
ATCC ATCC ICso
Ex. NCTC ATCC ATCC CCUG ATCC NCTC
BAA- BAA- rel to 13441 25922 4352 59347 27853 13424
2146 747 PMB*
D74 0.25 0.25 0.5 0.125 0.5 0.25 2 2 29.6
D75 0.125 0.06 0.125 0.06 0.5 0.5 0.125 0.06 10.1
D76 0.25 0.125 0.125 0.06 0.25 0.25 0.25 0.06 3.1
D77 0.06 0.06 0.125 0.125 1 0.5 0.06 0.06 13.3
D78 0.125 0.125 0.125 0.06 0.5 0.5 0.06 0.06 5.2
D79 0.125 0.125 0.125 0.06 0.25 0.25 0.125 0.06 7.5
D80 ND 0.5 ND 0.25 0.5 0.5 0.5 0.5 ND
D81 ND 0.06 0.06 0.06 0.5 0.25 0.06 0.03 ND
D82 ND 0.125 ND 0.06 4 2 0.125 0.06 ND
D83 0.06 0.125 ND 0.06 0.5 0.25 0.125 0.06 7.1
D84 0.06 0.25 ND 0.125 0.5 0.5 0.25 0.06 ND
D85 0.125 0.06 ND 0.06 0.25 0.125 0.06 <0.015 6.6
D86 ND 0.125 ND 0.03 0.5 0.25 0.06 0.03 ND
D87 ND 0.03 ND 0.06 1 0.25 0.03 0.03 18.9
D88 ND 0.06 ND 0.06 0.5 0.125 0.06 0.06 ND
D89 0.125 0.5 0.5 ND 1 0.5 0.5 0.5 2.6
D90 ND 0.25 ND 0.25 0.25 0.5 0.25 0.25 0.7
D91 ND 0.5 ND 0.25 0.5 0.5 0.5 0.25 ND
D92 ND 0.5 ND 0.25 0.5 0.25 0.25 0.5 2.7
D93 ND 0.25 ND 0.25 1 0.25 0.5 0.25 ND
D94 ND 0.03 ND ND 1 0.5 0.06 0.06 ND
* Figures represent the mean value obtained from up to three independent studies. Table 6D - MIC Values (micrograms/mL) for Example Compou nds and Comparator compounds polymyxin B, C1 , C2, and CC3 against strains of E. coli. K. pneumoniae, P. aeruginosa and A. baumanii with elevated MICs to Polymyxin B
Figure imgf000137_0001
Figure imgf000138_0001
Figure imgf000139_0001
Table 6E - MIC Values (micrograms/mL) and HK-2 cell toxicity relative to PMB for additional example compounds. PMB is included as a comparator.
Figure imgf000140_0001
Figure imgf000141_0001
Table 6F - MIC values (micrograms /mL) for additional example compounds against strains of E. coli. K. pneumoniae, P. aeruginosa and A. baumanii with elevated MICs to Polymyxin B. PMB is included as a comparator.
Figure imgf000142_0001
Figure imgf000143_0001
In vivo efficacy against P. aeruginosa ATCC 27853 thigh infection in mice
In this study, 4 male mice were used in each compound treatment group and 6 for vehicle control. Mice were rendered temporarily neutropenic by immunosuppression with cyclophosphamide at 150mg/kg 4 days before infection and 100 mg/kg 1 day before infection by intraperitoneal injection. 24 hours post the second round of
immunosuppression, mice were infected with P. aeruginosa ATCC27853 intramuscularly into both lateral thigh muscles under inhaled anaesthesia using ~ 2.5 to 5 x 105 CFU/mouse thigh. Compounds were administered in solution by intravenous (IV) bolus injection into the lateral tail vein. This was performed three times at 1 , 3.5 and 6 hours post infection at a dose volume of 10 mL/kg (0.25 mL/25g mouse). The vehicle control group was treated with 0.9% saline for injection also at 10 mL/kg IV thrice at 1 , 3.5 and 6 hours post infection.
At 1 hour post infection, 4 animals were humanely euthanized using pentabarbitone overdose to provide a pre-treatment control group. At 9 hours post infection, the clinical condition of all animals was assessed prior to them being humanely euthanized by pentabarbitone overdose. Animal weight was determined before both thighs were removed and weighed individually. Individual thigh tissue samples were homogenized in ice cold sterile phosphate buffered saline. Thigh homogenates were then quantitatively cultured onto cystine lactose electrolyte deficient (CLED) agar and incubated at 37°C for 24 hours before colonies were counted.
An in vivo mouse thigh efficacy study compared D9, D1 1 , D15 and D25 at 1 .7 mg/Kg and 3.4 mg/kg free base equivalent with Polymyxin sulphate at 0.85, 1 .7 and 3.4 mg/kg free base equivalent The infection level was ~ 1 x 104 CFU/mouse thigh. Results are given in Table 17.
Table 17 - Mean log-io reductions in P. aeruginosa ATCC 27853 burden recovered from mouse thighs following IV administration of compounds at 1 , 3.5 and 6 h post-infection in a 9h infection model.
Dose Log reduction from
Treatment
(mg/kg) vehicle (CFU/g)
Pre-treatment ND 1 .89
Vehicle ND 0.00
1 .7 0.67
D9
3.4 3.54 Dose Log reduction from
Treatment
(mg/kg) vehicle (CFU/g)
1 .7 3.42
D1 1
3.4 3.86
1 .7 0.19
D15
3.4 3.89
1 .7 3.10
D25
3.4 3.90
0.85 1 .19
Polymyxin B 1 .7 4.04
3.4 4.23
The doses in the table are indicated in mg drug base/kg.
All compounds gave > 3-log reduction in bacterial counts at a dose of 3.4 mg/kg free base equivalent. Examples D1 1 and D25 gave a > 3-log reduction in bacterial counts at dose of 1.7 mg/kg free base equivalent.
Further In vivo efficacy against Escherichia coli ATCC 25922 thigh infection in mice The in vivo efficacy of 5 compounds of the invention (D25, D31 , D36, D50 and D52) was evaluated in a 9 h mouse thigh infection model of E. coli. The model was set up as for the Pseudomonas infection as described herein using an inoculum of 3.3 x 105 CFU of
Escherichia coli isolate ATCC 25922 delivered into each thigh. The results are summarized in Table 18.
Test compounds were administered at two concentrations (equivalent to 0.43 and 1 .7 mg/kg free base). Three dose levels of polymyxin B sulphate were used as comparator (equivalent to 0.43, 1.7 and 3.4 mg/kg free base). The Results are given in Table 18. Table 18 - Mean logio reductions in E. coli ATCC 25922 burden recovered from mouse thighs following IV administration of compounds at 1 , 3.5 and 6 h post-infection in a 9h infection model
Dose (mg/kg/ dose) Mean logio CFU reduction vs.
Example free base control
0.43 3.72
Polymyxin B 1.7 4.08
3.4 4.32 Dose (mg/kg/ dose) Mean log-io CFU reduction vs.
Example free base control
0.43 3.31
D25
1.7 4.17
0.43 4.16
D31
1.7 4.37
0.43 4.50
D36
1.7 4.13
0.43 4.05
D50
1.7 4.33
0.43 3.57
D52
1 .47 4.04
All compounds gave a reduction in bacterial counts similar to or greater than that achieved by Polymyxin B at the same dose. Further In vivo efficacy against Acinetobacter baumannii NCTC 13301 - thigh infection in mice
The in vivo efficacy of 3 compounds of the invention (D36, D50 and D65) was evaluated in a mouse thigh infection model of A baumannii. The model was setup as described above, with the exception that compounds were delivered SC at 2, 6 and 10 h post-infection with thighs harvested at 16 h. post-infection. An inoculum of approx. 1 .4 x 105 CFU of A.
baumannii isolate NCTC 13301 was delivered into each mouse thigh. Test compounds and the comparator polymyxin B were administered at five concentrations (equivalent to 0.215, 0.86, 2.6, 8.6 and 17.2 mg/kg free base). The results are summarized in Table 19.
Table 19 - Mean og-io reductions in A. baumannii NCTC 13301 burden recovered from mouse thighs following SC administration of compounds at 2, 6 and 10 h post-infection in a 16h infection model.
Figure imgf000147_0001
All test compounds showed a good dose response and similar or greater efficacy than seen with the equivalent dose of polymyxin B.
Further in vivo efficacy against Acinetobacter baumannii NCTC 13301 - lung infection in mice
The in vivo efficacy of 2 compounds of the invention (D36, D65) was evaluated in a mouse lung infection model of A. baumanii. NCTC 13301. The results are summarized in Table 20. Groups of 7 male neutropenic specific-pathogen-free CD-1 mice weighing 21 .5-27.5g were used. On Day 0, animals were infected with 0.04 ml_ inoculum by intranasal instillation into mouse nostrils and were kept in an upright position on a string rack for -10 min postinfection. The inoculum concentration was approx. 8 x 108 CFU/ml of A baumannii isolate NCTC 13301 (3.5 x 107 CFU/lung). At 2 h, the CFU count was determined from 3 mice and the remaining mice (7 per test compound groups) were treated with a subcutaneous injection of the drug at + 2, 6 and 10 hr post-infection. Test compounds and the comparator polymyxin B were administered at four concentrations (2.6, 8.6, 17.2 and 25.8 mg/kg free base). The vehicle control group (7 mice) was treated with 0.9% saline for injection at 2, 6 and 10h post-infection.
Sixteen hours after infection, the mice were euthanized humanely. The lungs of each animal were harvested, homogenized and quantitatively cultured onto CLED agar for CFU determination. Decrease of the total CFU compared to control counts at 16h post-infection was determined for each dose group.
Table 20 - Mean log reductions in A. baumannii NCTC 13301 burden recovered from mouse lungs following SC administration of compounds at 2, 6 and 10 h post-infection in a 16h infection model.
Figure imgf000148_0001
Example D36 and D65 at all doses showed greater efficacy than observed with the equivalent dose of polymyxin B.
Further in vivo efficacy against Pseudomonas aeruginosa ATCC 27853 - lung infection in mice
The in vivo efficacy of 4 compounds of the invention (D25, D36, D42 and D50) was evaluated in a mouse lung infection model of P. aeruginosa ATCC 27853. The model was setup as described above with the exception that groups of up to 8 mice were inoculated through intranasal instillation of -2.5 x 106 CFUs of P. aeruginosa isolate ATCC 27853 (1 .0 x 105 CFU/lung). Test compounds were administered at two concentrations (equivalent to 4.3 and 17.2 mg/kg free base). Three dose levels of polymyxin B sulfate were used as comparator (equivalent to 4.3, 8.6 and 17.2 mg/kg free base). The results are summarized in Table 21 .
Table 21 - Mean logio reductions in P. aeruginosa ATCC 27853 burden recovered from mouse lungs following SC administration of compounds at 2, 6 and 10 h post-infection in 16h infection model.
Figure imgf000149_0001
All test compounds showed greater efficacy than seen with the equivalent dose of polymyxin B with many samples at or below the limit of detection of the model when the higher 17.2 mg/kg/dose was administered.
References All documents mentioned in this specification are incorporated herein by reference in their entirety. de Visser et at. J. Peptide Res, 61 , 2003, 298-306
GCC 2012/22819
Handbook of Pharmaceutical Excipients, 5th edition, 2005
Katsuma et al. Chem. Pharm. Bull. 2009; 57, 332-336
PCT/GB2012/052844,
Petrosillo et al. Clin. Microbiol. Infect. 2008; 14, 816-827
Quale et at. Microb. Drug Resist. 2012; 18, 132-136
Remington's Pharmaceutical Sciences, 18th edition, Mack Publishing Company, Easton, Pa., 1990
Sato et at. Chem. Pharm. Bull. 201 1 ; 59, 597-602
TW 101 142961
US 8,415,307 Vaara et al, Antimicrob. Agents and Chemotherapy, 52, 2008. 3229-3236
Vaara et al. Microbiol. Rev. 1992; 56, 395-41 1
WO 1988/00950
WO 2008/017734
WO 2010/075416
WO 2012/168820
Yamada et al, J. Peptide Res. 64, 2004, 43-50
Yousef et al., Antimicrob. Agents Chemother. 201 1 , 55, 4044-4049

Claims

Claims:
1. A compound of formula
Figure imgf000151_0001
and pharmaceutically acceptable salts, protected forms, solvates and hydrates thereof, such as pharmaceutically acceptable salts, and hydrates thereof. wherein: -X- represents -C(O)-, -NHC(O)-, -OC(O)-, -CH2- or -SO2-;
-R1 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is a phenylalanine, leucine or valine residue;
-R2 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is a leucine, iso-leucine, phenylalanine, threonine, valine or nor-valine residue;
-R3 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is a threonine or leucine residue;
-R4 is C1-6 alkyl substituted with one hydroxyl group or one amino group;
-R15 is an amino-containing group:
16R17
Figure imgf000151_0002
where:
-RA is -LA-RAA or hydrogen;
-Q- is a covalent bond or -CH(RB)-;
-RB is hydrogen or -LB-RBB; or, where -Q- is -CH(RB)-, -RA and -RB together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or -RA and -RB together form a 5- to 10-monocyclic or bicyclic heterocycle; and, where -Q- is a covalent bond, -RA is -LAR^, and where -Q- is -CH(RB)- one or both of -RA and -RB is not hydrogen;
-R16 is independently hydrogen or C1-4 alkyl;
-R17 is independently hydrogen or C1-4 alkyl;
or -NR16R17 is a guanidine group;
or -R17 and -RA together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle;
or, where -Q- is -CH(RB)-, -R17 and -RB together form a 5- to 10-membered nitrogen-containing monocyclic or bicyclic heterocycle; and where -R17 and -RA together form a monocyclic nitrogen-containing heterocycle, each ring carbon atom in -R17 and -RA is optionally mono- or di-substituted with -Rc, and the monocyclic heterocycle is substituted with at least one group selected from -Rc, -RN, -RNA and -LB-RBB, where present,
and where -R17 and -RB together form a monocyclic nitrogen-containing heterocycle, each ring carbon atom in -R17 and -RB is optionally mono- or di- substituted with -Rc, and the monocyclic heterocycle is substituted with at least one group selected from -Rc, and -RN, where present, or the monocyclic heterocycle is optionally substituted when -RA is -L R^,
and a monocyclic nitrogen-containing heterocycle optionally contains one further nitrogen, oxygen or sulfur ring atom, and where a further nitrogen ring atom is present it is optionally substituted with -RN, with the exception of a further nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; where -R17 and -RA or -R17 and -RB together form a bicyclic nitrogen- containing heterocycle, each ring carbon atom in -R17 and -RA or -R17 and -RB is optionally mono- or di-substituted with -RD;
and the bicyclic nitrogen-containing ring atom heterocycle optionally contains one, two or three further heteroatoms, where each heteroatom is independently selected from the group consisting of nitrogen, oxygen and sulfur, and where further nitrogen ring atoms are present, each further nitrogen ring atom is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; where -RA and -RB together form a 5- to 10-membered monocyclic carbocycle or heterocycle, each ring carbon atom in -RA and -RB is optionally mono- or di-substituted with -Rc, and a nitrogen ring atom, where present in the monocyclic heterocycle, is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; where -RA and -RB together form a 5- to 10-membered bicyclic carbocycle or heterocycle, each ring carbon atom in -RA and -RB is optionally mono- or
di-substituted with -RD, and a nitrogen ring atom, where present in the bicyclic heterocycle, is optionally substituted with -RN, with the exception of a nitrogen ring atom that is connected to the carbon that is a to the group -X-, which nitrogen ring atom is optionally substituted with -RNA; and where R17 and -RA or -R17 and -RB together form a 5- to 10-membered nitrogen- containing monocyclic or bicyclic heterocycle, or where -RA and -RB together form a 5- to 10-membered monocyclic or bicyclic carbocycle, or together form a 5- to 10-membered monocyclic or bicyclic heterocycle, a carbon ring atom in -R17 and -RA, -R17 and -RB, or -RA and -RB is optionally alternatively substituted with oxo (=0); each -Rc is independently -Lc-Rcc;
each -RD is independently selected from -Rc, halo, -NO2, -OH, and -N H2; each -RN is independently -|_N-RNN;
each -RNA is independently -RL-RNN or -RNN;
-RAA, -RBB, and each -Rcc and -RNN where present, is independently selected from C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, and C5-12 aryl; each -LA- is independently a covalent bond or a linking group selected from -RL-*, -O-L^-*, -00(0)-^-*, -N(R11)-LAA-*, and -0(0)-^-*, where the asterisk indicates the point of attachment of the group -LA- to -RAA; each -LB- and -Lc- is independently a covalent bond or a linking group selected from -RL- *, -O-L^-*, -OC(0)-LAA-*,-N(R11)-LAA-*, -N(R11)C(0)-LAA-*, -0(0)-^-*, -C(0)0-LAA-*, and -C(0)N(R11)- LAA-*, and optionally further selected from -N(R11)S(0)-LAA-*,
-N(R11)S(0)2-LAA-*, -S(0)N(R11)-LAA-*, and -S(0)2N(R11)-LAA-*where the asterisk indicates the point of attachment of the group -LB- to -RBB or the group -Lc- to -Rcc; each -LN- is independently a covalent bond or a group selected from -S(0)-LAA-*, -S ^-L^-*, -0(0)-^-* and -C(0)N(R11)-LAA-*, where the asterisk indicates the point of attachment of the group -LN- to -RNN; and each -LAA- is independently a covalent bond or -RL-; and each -RL- is independently selected from C1-12 alkylene, C2-12 heteroalkylene, C3-10 cycloalkylene and C5-10 heterocyclylene, and where -L^- is connected to a group C1-12 alkyl, -RL- is not C1-12 alkylene; and each C1-12 alkyl, C3-10 cycloalkyl, C4-10 heterocyclyl, C5-12 aryl, C1-12 alkylene, C2-12 heteroalkylene, C3-10 cycloalkylene and C5-10 heterocyclylene group is optionally substituted, where -Rs is an optional substituent to carbon and -R12 is an optional substituent to nitrogen; each -Rs is independently selected from -OH, -OR12, -OC(0)R12, halo, -R12, -NHR12, -NR12R13, -NHC(0)R12, -N(R12)C(0)R12, -SH, -SR12, -C(0)R12, -C(0)OH, -C(0)OR12, -C(0)NH2, -C(0)NHR12 and C(0)NR12R13; except that -R12 is not a substituent to a C1-12 alkyl group; or where a carbon atom is di-substituted with -Rs, these groups may together with the carbon to which they are attached form a C3-6 carbocycle or a C5-6 heterocycle, where the carbocycle and the heterocycle are optionally substituted with one or more groups -R12; each -R12 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl;
each -R13 is independently C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl;
or -R12 and -R13, where attached to N, may together form a 5- or 6-membered heterocyclic ring, which is optionally substituted with C1-6 alkyl, C1-6 haloalkyl, phenyl or benzyl; each -R11 is independently hydrogen or C1-4 alkyl; and -R8 is hydrogen or methyl.
2. The compound of claim 1 , wherein -X- is -C(O)-.
3. The compound of any one of the preceding claims, wherein -R8 is methyl.
4. The compound of any one of the preceding claims, wherein -R1 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a phenylalanine residue.
5. The compound of any one of the preceding claims, wherein -R2 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a leucine residue.
6. The compound of any one of the preceding claims, wherein -R3 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is a threonine residue.
7. The compound of any one of the preceding claims, wherein -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached, is α,γ-diaminobutyric acid (Dab), a serine residue, a threonine residue, a lysine residue, an ornithine residue, or α,β-diaminopropionic acid (Dap).
8. The compound according to claim 7, wherein -R4 together with the carbonyl group and nitrogen alpha to the carbon to which it is attached is α,γ-diaminobutyric acid (Dab).
9. The compound of any one of the preceding claims, wherein -R15 is an amino- containing group:
Figure imgf000155_0001
10. The compound of any one of the preceding claims, wherein -Q- is a covalent bond.
1 1 . The compound of any one of claims 1 to 9, wherein -Q- is -CH(RB)-.
12. The compound of any one of the preceding claims, wherein -R16 is hydrogen.
13. The compound of any one of the preceding claims, wherein -R17 is hydrogen.
14. The compound of any one of claims 1 to 12, wherein -R17 and -RA together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle.
15. The compound of any one of claims 1 to 12, wherein -R17 and -RB together with the carbon atoms to which they are attached, form a nitrogen-containing heterocycle.
* * * *
16. The compound of any one of claims 1 to 13, wherein -RA is -LA-R'
17. The compound of claim 1 1 , wherein -RB is -LB-RBB.
18. The compound of any one of claims 1 to 8, wherein -R15 is selected from the group consisting of:
Figure imgf000156_0001
wherein -RC1 is hydrogen or -Rc and -RN1 is hydrogen or -RNA.
The compound of claim 18, wherein -R15 is selected from the group consisting of:
Figure imgf000156_0002
The compound of cl im 18, wherein -R15 is selected from the group consisting of:
Figure imgf000156_0003
21 . The compound of claim 19, wherein -R15 is selected from the group consisting of:
Figure imgf000156_0004
22. The compound of claim 20, wherein -R15 is:
Figure imgf000157_0001
23. The compound of any one of claims 18 to 22, wherein -RA is -LA-RAA.
24. The compound of claim 23, wherein -LA- is a covalent bond.
25. The compound of claim 23, wherein -LA- is C1-12 alkylene. 26. The compound of claim 25, wherein -LA- is -CH2-.
27. The compound of any one of claims 18 to 26, wherein -RM is C1-12 alkyl, such as C6-10 alkyl, optionally substituted with one or more groups -Rs. 28. The compound of claim 27, wherein -RAA is C1-12 alkyl, such as Ce-ιο alkyl.
29. The compound of any one of claims 18 to 26, wherein -RM is C5-12 aryl, optionally substituted with one or more groups -Rs or one or more groups -RN. 30. The compound of claim 29, wherein -RAA is C5-12 aryl.
31 . The compound of claim 29, wherein -RAA is phenyl optionally substituted with one or more groups -Rs. 32. The compound of any one of claims 18-21 , wherein -R15 is:
Figure imgf000157_0002
33. The compound of any one of claims 18-21 and 32, wherein -RBB is -LB-RBB. 34. The compound of claim 33, wherein -LB- is a covalent bond.
35. The compound of claim 33, wherein -LB- is C1-12 alkylene.
36. The compound of claim 33, wherein -LB- is -CH2-.
37. The compound of any one of claims 18-21 and 32-36, wherein -RBB is independently a group selected from C1-12 alkyl, C4-10 heterocyclyl, and C5-12 aryl, and each group is optionally substituted with one or more groups -Rs or one or more groups -RN. 38. The compound of claim 37, wherein -RBB is C1-12 alkyl, optionally substituted with one or more groups -Rs.
39. The compound of claim 38, wherein -RBB is C1-12 alkyl. 40. The compound of any one of claims 18 to 39, wherein -R16 and -R17 are each hydrogen.
* * * * *
The compound of claim 18, wherein -R15 is selected from the group consisting of:
Figure imgf000158_0001
The compound of claim 41 , wherein -R15 is selected from the group consisting of:
Figure imgf000158_0002
43. The compound of claim 41 , wherein -R15 is:
Figure imgf000158_0003
The compound of claim 43, wherein -R15 is selected from the group consisting of:
Figure imgf000158_0004
The compound of claim 44, wherein -R15 is selected from the group consisting of:
Figure imgf000159_0001
46. The compound of claim 44, wherein -R15 is:
Figure imgf000159_0002
47. The compound of any one of claims 44 to 46, wherein -Rc is -Lc-Rcc.
48. The compound of claim 47, wherein -Lc- is a covalent bond.
49. The compound of claim 47, wherein -Lc- is C1-12 alkylene.
50. The compound of claim 47, wherein -Lc- is -CH2-. 51 . The compound of any one of claims 44 to 50, wherein -Rcc is C1-12 alkyl, optionally substituted with one or more groups -Rs.
52. The compound of claim 51 , wherein -Rcc is C1-12 alkyl. 53. The compound of any one of claims 44 to 50, wherein -Rcc is C5-12 aryl, optionally substituted with one or more groups -Rs or one or more groups -RN.
54. The compound of claim 53, wherein -Rcc is C5-12 aryl, such as phenyl. 55. The compound of any one of claims 44 to 50, wherein -Rcc is C3-10 cycloalkyl, optionally substituted with one or more groups -Rs.
56. The compound of claim 55, wherein -Rcc is C3-10 cycloalkyl, such as cyclohexyl. 57. The compound of claim 44, wherein -R15 is:
Figure imgf000159_0003
58. The compound of any one of claims 41-42 or claim 57, wherein -RNA is -RNN or -RL-RNN. 59. The compound of claim 58 where -RL- is C1-12 alkylene.
60. The compound of claim 58, wherein -RL- is -CH2-.
61 . The compound of any one of claims 41-42 or claims 57-60, wherein -RNN is C1-12 alkyl, optionally substituted with one or more groups -Rs.
62. The compound of claim 61 , wherein -RNN is C1-12 alkyl.
63. The compound of any one of claims 41-42 or claims 57-60, wherein -RNN is C5-12 aryl, optionally substituted with one or more groups -Rs or one or more groups -RN.
64. The compound of claim 63, wherein -RNN is C5-12 aryl, such as phenyl.
65. The compound of claim 41 , wherein -R15 is:
1
R
Figure imgf000160_0001
66. The compound of claim 65, wherein -Rc is -Lc-Rcc.
67. The compound of claim 66, wherein -Lc- is a covalent bond.
68. The compound of claim 66, wherein -Lc- is C1-12 alkylene.
69. The compound of claim 66, wherein -Lc- is -CH2-. 70. The compound of any one of claims 65 to 69, wherein -Rcc is C1-12 alkyl, optionally substituted with one or more groups -Rs.
71 . The compound of claim 70, wherein -Rcc is C1-12 alkyl. 72. The compound of any one of claims 65 to 69, wherein -Rcc is C5-12 aryl, optionally substituted with one or more groups -Rs or one or more groups -RN.
73. The compound of claim 72, wherein -Rcc is C5-12 aryl, such as phenyl. The compound of any one of claims 41 to 73, wherein -R16 is hydrogen.
75 The compound of any one of the preceding claims, wherein -Rs, where present, is independently selected from -OR12, halo, and -R12.
* * * * *
76. A pharmaceutical composition comprising a compound of any one of claims 1 to 75 and a biologically acceptable excipient, optionally together with a second active agent.
77. A compound of any one of claims 1 to 75 or a pharmaceutical composition of claim 86 for use in a method of treatment.
78. A compound of any one of paragraphs 1 to 75 or a pharmaceutical composition of claim 76 for use in a method of treating a microbial infection.
79. A compound of any one of claims 1 to 75 or a pharmaceutical composition of claim 76 for use in a method of treating a microbial infection, wherein the method comprising treating the infection with the compound of formula (III) and an active agent selected from the group consisting of rifampicin, fusidic acid, novobiocin, oxacillin, azithromycin, aztreonam, meropenem, tigecycline, and ciprofloxacin, and pharmaceutically acceptable salts and solvates thereof.
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JP2017510570A (en) 2017-04-13
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MX359104B (en) 2018-09-14
AU2015228898A1 (en) 2016-10-20
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JP6785659B2 (en) 2020-11-18
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RU2740190C2 (en) 2021-01-12
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