Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/547—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom
  • C07F9/553—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom
  • C07F9/5537—Heterocyclic compounds, e.g. containing phosphorus as a ring hetero atom having one nitrogen atom as the only ring hetero atom the heteroring containing the structure -C(=O)-N-C(=O)- (both carbon atoms belong to the heteroring)
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K31/00—Medicinal preparations containing organic active ingredients
  • A61K31/66—Phosphorus compounds
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P25/00—Drugs for disorders of the nervous system
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
  • C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic Table
  • C07F9/02—Phosphorus compounds
  • C07F9/28—Phosphorus compounds with one or more P—C bonds
  • C07F9/30—Phosphinic acids [R2P(=O)(OH)]; Thiophosphinic acids ; [R2P(=X1)(X2H) (X1, X2 are each independently O, S or Se)]
  • C07F9/301—Acyclic saturated acids which can have further substituents on alkyl

Definitions

• the present invention relates to the use in therapy, in particular as selective GABA B receptor agonists, of certain phosphinic acid derivatives, pharmaceutical compositions containing said derivatives and intermediates useful in their preparation.
• EP-0181833-A1 (equivalent to US 4,656,298) discloses compounds of structure
• R 1 to R 3 can be, for example, hydrogen, C 1 _ 8 alkyl or phenyl, as having GABA B receptor agonist and antagonist properties and also mixed GABA A and GABA B receptor agonist properties.
• Compounds having activity as GABA B receptor agonists can be used as muscle relaxants, and compounds combining GABA ⁇ with GABA A receptor agonist properties may be used as antidepressants.
• Compounds having GABA B receptor antagonist properties are expected to act as muscle stimulants and be active in muscular atrophy and distrophy. In view of the variation in potential utilities depending on the precise nature of the affinity of compounds at the different receptor sites clearly there is a need for compounds having greater specificity for the different receptor sites.
• the present invention therefore provides, in a first aspect, the use of a 3-(aminopropyl) ethyl phosphinic acid of structure (I)
• Suitable pharmaceutically acceptable salts of the compound (I) include for example the corresponding acid addition salts.
• Suitable acids for the formation of such salts include, for example, mineral acids such as hydrochloric, hydrobromic, sulphuric or phosphoric acid, or organic acids such as organic sulphonic acids, for example, benzenesulphonic, p-toluenesulphonic or methansulphonic acid, and organic carboxylic acids, such as acetic, lactic, palmitic, stearic, maleic, maleic, fumaric, tartaric, ascorbic or citric acid.
• suitable metal ions such as sodium, potassium, lithium or magnesium ions. It is to be noted, and will be appreciated by persons skilled in the art that under appropriate pH conditions the compound of structure (I) can exist in Zwitterionic
• the compound of structure (I) and salts thereof can be prepared by processes known in the art, for example by,
• R is a protecting group and X is a protected a ino group
• R 1 is hydrogen or a protecting group
• Suitable protected amino groups X will be apparent to those skilled in the art, and include, for example, acylamino groups such as acetyla ino, phthalimido, benzyloxycarbonyla ino or t-butyloxycarbonylamino or arylC 1 _ 4 alkylamino groups e.g. benzylamino.
• a preferred protected amino group X is phthalimido.
• Suitable protecting groups R will be apparent to those skilled in the art and include, for example C 1 __ 4 -alkyl, in particular ethyl and C 1-4 aralkyl, in particular benzyl.
• Suitable protecting groups R 1 will be apparent to those skilled in the art and include for example, C 1 _ 4 alkyl, in particular ethyl and trimethylsilyl.
• Suitable conditions for hydrolysis of the compounds of structure (II) will be apparent to those skilled in the art.
• the deprotection can be carried out under aqueous conditions in the presence of hydrochloric acid and acetic acid at reflux temperature.
• R is C 1 _ 4 aralkyl, for example benzyl
• the deprotection can be carried out by hydrogenation in the presence of a suitable catalyst, for example platinum or palladium on carbon.
• Suitable conditions for th reduction of compounds of structure (III) will be apparent to those skilled in the art and include, for example Raney nickel in a suitable solvent, such as a C 1 _ 4 alkanol, in particular ethanol and in the presence of ammonia.
• Protecting groups R 1 can be removed by standard techniques, for example if R 1 is ethyl by hydrolysis in the presence of a suitable acid such as hydrochloric acid.
• the compounds of structure (II) which themselves are new and form a further aspect of the invention can be prepared, for example, when in structure (II) X is phthalimido and R is Et, by reaction of diethyl methyl phosphonite (prepared according to Hoffman, F. . and Moore T.R. JACS, 1958, 8j0, 1150-1154) and N-(3-bromopropyl)phthalamide, in an organic solvent, in particular toluene at elevated temperature.
• compounds of structure (III) which are themselves novel and form a further aspect of the invention can also be prepared by procedures analogous to those known in the art.
• compounds of structure (III) in which R 1 is ethyl can be prepared by reaction of diethyl methyl phosphonite and 2-bromopropionitrile.
• compounds of structure (III) in which R 1 is trimethylsilyl can be prepared by reaction of methyl phosphinic acid with trimethylsilylchloride in the presence of a suitable base such as triethylamine, followed by reaction with acrylonitrile.
• the compound of structure (I) has been found to be an extremely potent and selective agonist of GABA B receptor sites.
• the compound has been found in in vitro binding assays to be significantly more potent than the known GABA B agonist baclofen and, surprisingly, much more selective for the GABA B receptor than the GABA A receptor when compared to the known selective GABA B agonist 3-aminopropyl phosphinic acid disclosed in EP-0181833-A1.
• the following IC 50 values were derived from inhibition of specific GABA B or GABA A binding to rat synaptic membranes for 3-(aminopropyl)methyl phosphinic acid (example 1) baclofen and 3-aminopropyl phosphinic acid..
• Potent selective GABA B agonists are expected to be of use in therapy in particular in the treatment of disorders of the central nervous system such as, multiple sclerosis, muscle relaxation in spinal spasticity, cerebral palsy, trigeminus neuralgia, pain and drug withdrawal symptoms, and other nervous disorders.
• cardiovascular disorders such as hypertension, gut motility disorders such as irritable bowel syndrome and as prokinetic agents.
• the present invention therefore provides a method of treatment of the aforementioned disease states which comprises administering to a subject in need thereof an effective amount of a compound of structure (I) or a pharmaceutically acceptable salt thereof.
• the compounds of the present invention ' are generally formulated into a pharmaceutical composition before administration.
• a pharmaceutical composition comprising a compound of structure (I) or a pharmaceutically acceptable salt thereof in association with a pharmaceutically acceptable carrier.
• compositions of the present invention are prepared using standard pharmaceutical techniques and excipients for the preparation of suitable oral or parenteral compositions.
• compositions for oral use can be in the form of liquid such as syrups, suspensions or emulsions, tablets, capsules and lozenges.
• a liquid formulation will generally consist of a suspension or solution of the compound or pharmaceutically acceptable salt in a suitable liquid carrier(s) for example, ethanol, glycerine, non-aqueous solvent, for example polyethylene glycol, oils, or water with a suspending agent, preservative, flavouring or colouring agent.
• a suitable liquid carrier(s) for example, ethanol, glycerine, non-aqueous solvent, for example polyethylene glycol, oils, or water with a suspending agent, preservative, flavouring or colouring agent.
• a composition in the form of a tablet can be prepared using any suitable pharmaceutical carrier(s) routinely used for preparing solid formulations.
• suitable pharmaceutical carrier(s) include magnesium stearate, starch, lactose, sucrose and cellulose.
• a composition in the form of a capsule can be prepared using routine encapsulation procedures.
• pellets containing the active ingredient can be prepared using standard carriers and then filled into a hard gelatin capsule; alternatively, a dispersion or suspension can be prepared using any suitable pharmaceutical carrier(s), for example aqueous gums, celluloses, silicates or oils and the dispersion or suspension then filled into a soft gelatin capsule.
• Typical parenteral compositions consist of a solution or suspension of the compound or pharmaceutically acceptable salt in a sterile aqueous carrier or parenterally acceptable oil, for example polyethylene glycol, polyvinyl pyrrolidone, lecithin, arachis oil or sesame oil.
• a sterile aqueous carrier or parenterally acceptable oil for example polyethylene glycol, polyvinyl pyrrolidone, lecithin, arachis oil or sesame oil.
• the solution can be lyophilised and then reconstituted with a suitable solvent just prior to administration.
• a typical suppository formulation comprises a compound of formula (I) or a pharmaceutically acceptable salt thereof which is active when administered in this way, with a binding and/or lubricating agent such as polymeric glycols, gelatins or cocoa butter or other low melting vegetable or synthetic waxes or fats.
• a binding and/or lubricating agent such as polymeric glycols, gelatins or cocoa butter or other low melting vegetable or synthetic waxes or fats.
• composition is in unit dose form such as a tablet or capsule.
• Each dosage unit for oral administration contains preferably from 1 to 250 mg (and for parenteral administration contains preferably from 0.1 to 25 mg) of a compound of the formula (I) or a pharmaceutically acceptable salt thereof " calculated as the free base.
• the daily dosage regimen for an adult patient may be, for example, an oral dose of between 1 mg and 500 mg, preferably between 1 mg and 250 mg, or an intravenous, subcutaneous, or intramuscular dose of between 0.1 mg and 100 mg, preferably between 0.1 mg and 25 mg, of the compound of the formula (I) or a pharmaceutically acceptable salt thereof calculated as the free base, the compound being administered 1 to 4 times per day.
• the compounds will be administered for a period of continuous therapy, for example for a week or more.
• the supernatant was used to rinse off the upper layer of the pellet with the aid of a Pasteur pipette.
• the combined suspension was centrifuged for 20 minutes at 48,000 g.
• the final crude synaptic membranes were washed twice with distilled water and were either resuspended in buffer for further washing prior to use as fresh tissue or were stored frozen at -20°C.
• [" • *_]-GABA (10 nM final concentrations 65 Ci/mmol) was added to each tube with or without varying concentrations of unlabelled test compound (final volume 1.0 ml). All drugs were made up using either buffer solution or distilled water for subsequent dilution into incubation solution. Where additional compounds were required to be present throughout the incubation, these were added to the buffer solution containing the membranes, just prior to the addition of 3 H-GABA. The final mixture was incubated under the required conditions (10 minutes at room temperature) and the assay was terminated by centrifugation at 7,500 g for 10 minutes. GABA B binding was determined by using 3 H-GABA in the presence of isoguvacine (40 ⁇ M) , a GABA A receptor ligand.
• GABA A binding was measured using 3 H-GABA in the presence of baclofen (100 ⁇ M) , a specific GABA B receptor ligand. Non-specific binding was obtained by incubation under GABA B conditions in the additional presence of 100 ⁇ M baclofen and under GABA A conditions in the additional presence of 100 ⁇ M isoguvacine. Following centrifugation the supernatant was aspirated off and the pellet rinsed twice superficially with ice- cold buffer solution.
• the tissue was digested using 'Soluene-350' tissue solubilizer at 35°C and the test tube and its contents were transferred to a scintillation vial containing 400 ⁇ l of 0.2 M HCl to neutralize the Soluene / .
• the tritium content of each sample was estimated by liquid scintillation spectrometry.
• Non-speci ic binding was subtracted from the total amount of radioactivity bound in the absence of any drug to yield the amount of ligand specifically bound.
• the amount of radioactivity specifically bound at a given concentration of non-radioactive drug was expressed as a percentage of the total ligand specifically bound.

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Citations (2)

• 1988
  • 1988-08-26 GB GB888820266A patent/GB8820266D0/en active Pending
• 1989
  • 1989-08-16 DE DE8989308311T patent/DE68901961T2/de not_active Expired - Lifetime
  • 1989-08-16 ES ES89308311T patent/ES2043025T3/es not_active Expired - Lifetime
  • 1989-08-16 EP EP89308311A patent/EP0356128B1/en not_active Expired - Lifetime
  • 1989-08-16 AT AT89308311T patent/ATE77747T1/de not_active IP Right Cessation
  • 1989-08-23 WO PCT/GB1989/000981 patent/WO1990001936A1/en not_active Ceased
  • 1989-08-23 AU AU42043/89A patent/AU614668B2/en not_active Ceased
  • 1989-08-23 JP JP1509477A patent/JPH03502101A/ja active Pending
  • 1989-08-23 PT PT91525A patent/PT91525B/pt not_active IP Right Cessation
  • 1989-08-25 IE IE892738A patent/IE892738L/xx unknown
  • 1989-08-25 ZA ZA896504A patent/ZA896504B/xx unknown
• 1990
  • 1990-04-25 DK DK101990A patent/DK101990A/da not_active Application Discontinuation
• 1992
  • 1992-07-02 GR GR920401249T patent/GR3005094T3/el unknown

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