Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D305/00—Heterocyclic compounds containing four-membered rings having one oxygen atom as the only ring hetero atoms
  • C07D305/14—Heterocyclic compounds containing four-membered rings having one oxygen atom as the only ring hetero atoms condensed with carbocyclic rings or ring systems
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
  • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
  • A61K47/51—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent
  • A61K47/56—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an organic macromolecular compound, e.g. an oligomeric, polymeric or dendrimeric molecule
  • A61K47/59—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an organic macromolecular compound, e.g. an oligomeric, polymeric or dendrimeric molecule obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyureas or polyurethanes
  • A61K47/60—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an organic macromolecular compound, e.g. an oligomeric, polymeric or dendrimeric molecule obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyureas or polyurethanes the organic macromolecular compound being a polyoxyalkylene oligomer, polymer or dendrimer, e.g. PEG, PPG, PEO or polyglycerol
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
  • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
  • A61K47/51—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent
  • A61K47/68—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an antibody, an immunoglobulin or a fragment thereof, e.g. an Fc-fragment
  • A61K47/6801—Drug-antibody or immunoglobulin conjugates defined by the pharmacologically or therapeutically active agent
  • A61K47/6803—Drugs conjugated to an antibody or immunoglobulin, e.g. cisplatin-antibody conjugates
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
  • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
  • A61K47/51—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent
  • A61K47/68—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an antibody, an immunoglobulin or a fragment thereof, e.g. an Fc-fragment
  • A61K47/6889—Conjugates wherein the antibody being the modifying agent and wherein the linker, binder or spacer confers particular properties to the conjugates, e.g. peptidic enzyme-labile linkers or acid-labile linkers, providing for an acid-labile immuno conjugate wherein the drug may be released from its antibody conjugated part in an acidic, e.g. tumoural or environment
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P35/00—Antineoplastic agents
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00

Definitions

• the present invention relates to novel cytotoxic agents with enhanced water solubility and their therapeutic uses. More specifically, the invention relates to novel cytotoxic agents that are taxanes which comprise both a polyethylene glycol moiety that enhances water solubility and a means of chemical linkage to a cell binding agent. These taxanes can be chemically linked to cell binding agents to provide therapeutics that are delivered to specific cell populations in a targeted manner.
• Cytotoxic drugs such as methotrexate, daunorubicin, doxorubicin, vincristine, vinblastine, melphalan, mitomycin C, chlorambucil, calicheamicin and maytansinoids have been conjugated to a variety of murine monoclonal antibodies.
• the drug molecules were linked to the antibody molecules through an intermediary carrier molecule such as serum albumin (Garnett et al, 46 Cancer Res. 2407-2412 (1986); Ohkawa et al, 23 Cancer Immunol. Immunother. 81-86 (1986); Endo et al, 47 Cancer Res. 1076-1080 (1980)), dextran (Hurwitz et al, 2 Appl. Biochem.
• Taxanes are mitotic spindle poisons that inhibit the depolymerization of tubulin, resulting in an increase in the rate of microtubule assembly and cell death. While docetaxel and paclitaxel are useful agents in the treatment of cancer, their antitumor activity is limited because of their non-specific toxicity towards normal cells.
• One object of the present invention is to provide novel taxanes that incorporate a polyethylene glycol moiety that confers enhanced aqueous solubility.
• Another object of the present invention is to provide polyethylene glycol- containing taxanes that are highly cytotoxic in vitro and that can still be effectively used in the treatment of many diseases.
• a taxane comprising a polyethylene glycol-containing linking group at C-7 or C-10, the linking group being capable of linking the taxanes to a cell binding agent or other chemical moiety.
• the invention also provides a cytotoxic agent comprising one or more taxanes linked to a cell binding agent through a polyethylene glycol-containing linking group at C-7 or C-10 of at least one of the taxanes.
• the present invention also provides a therapeutic composition
• a therapeutic composition comprising an effective amount of a cytotoxic agent comprising one or more taxanes linked to a cell binding agent through a polyethylene glycol-containing linking group at C-7 or C-10 of at least one of the taxanes; and (B) A pharmaceutically acceptable carrier, diluent, or excipient.
• the present invention also provides a method of killing selected cell populations comprising contacting the target cells or tissue containing target cells with a cytotoxic amount of the above-described cytotoxic agent.
• Figure 1 is a chemical formula that represents structures of various taxanes, including some of the more potent taxanes described in U.S. Patents 6,340,701 and
• Figure 2 is a chemical formula that represents structures of some of the polyethylene glycol-containing taxanes according to the present invention.
• Figure 3 shows the structure of 10-deacetylbaccatin III, which is the starting material for preparing the taxanes of the present invention and the structure of the parent taxoid.
• Figures 4-8 show the synthetic schemes for the preparation of polyethylene glycol-containing taxanes of the present invention.
• Figures 9, 10 and 11 show the in vitro cytotoxicity of polyethylene glycol- containing taxanes according to the present invention.
• This invention is based on the synthesis of novel taxanes that retain high cytotoxicity and that can be linked effectively to cell binding agents. It has previously been shown that the linkage of highly cytotoxic drugs to antibodies using a cleavable link, such as a disulfide bond, ensures the release of fully active drug inside the cell, and such conjugates are cytotoxic in an antigen specific manner (RN.J. Chari et al, 52 Cancer Res. 127-131 (1992); USP 5,475,092; and USP 5,416,064, 6,340,701 and 6,372,738). However, the art reveals that it is extremely difficult to modify drugs to improve their aqueous solubility without eliminating their cytotoxic potential.
• the disclosed invention overcomes this problem by modifying the disclosed taxanes with chemical moieties, and especially ones containing polyethylene glycol groups, to which appropriate cell binding agents can be linked.
• the disclosed novel taxanes have greater water solubility along with higher cytotoxic potency than that of known taxanes.
• the cell binding agent-taxane conjugates permit the full measure of the cytotoxic action of the taxanes to be applied in a targeted fashion against unwanted cells only, therefore, avoiding side effects due to damage to non-targeted healthy cells.
• This invention facilitates the linkage of taxanes to cell binding agents in aqueous media which had previously been difficult.
• the invention provides useful agents for the elimination of diseased or abnormal cells that are to be killed, lysed, or destroyed, such as tumor cells (particularly solid tumor cells), virus infected cells, microorganism infected cells, parasite infected cells, autoimmune cells (cells that produce autoantibodies), activated cells (those involved in graft rejection or graft vs. host disease), or any other type of diseased or abnormal cells, while exhibiting a minimum of side effects.
• the cytotoxic agent according to the present invention comprises one or more polyethylene glycol-containing taxanes linked to a cell binding agent via a linking group.
• the linking group is part of a chemical moiety that is covalently bound to a taxane through conventional methods.
• the chemical moiety can be covalently bound to the taxane via a disulfide linkage.
• taxanes useful in the present invention may have the formula (I) shown below:
• novel taxanes of the invention can be divided into two embodiments, (1) and (2) based on the position of the PEG substituent bearing a linking group.
• Ri can be H, an electron withdrawing group, such as F,
• R and R 7 are the same or different and each can be H, linear, branched, or cyclic alkyl groups having 1 to 10 carbon atoms, or simple or substituted aryl having
• R 8 can be linear, branched or cyclic alkyl having 1 to 10 carbon atoms.
• R ⁇ and R 7 are each H or are alkyl or aryl groups having 1 to 4 carbon atoms.
• Examples of preferred -NR 6 R groups include dimethyl amino, diethyl amino, dipropyl amino, and dibutyl amino, where the butyl moiety is any of primary, secondary, tertiary or isobutyl.
• Ri is preferably OMe, OEt, CI, F, NO 2 , or CF 3 .
• Ri is in the meta position and Ri' is OMe, and R
• R can be -OC(CH 3 ) 3 or -C 6 H 5 .
• R 2 is a PEG-containing linking group and R 5 can be H, a heterocyclic, a linear, branched, or cyclic ester or ether having from 1 to 10 carbon atoms or a carbamate of the formula -CNR] 0 R ⁇ , wherein R 10 and R ⁇ are the same or different and can be H, linear, branched, or cyclic alkyl having 1 to 10 atoms or simple or substituted aryl.
• preferred examples include -COCH 3 -COCH 2 CH 5 and -COCH 2 CH 2 CH 3 .
• preferred examples include -CONHCH 2 CH 3> -CONHCH 2 CH 2 CH 3 , -CO-morpholino, -CO-piperazino, -CO- piperidino, or -CO-N-methylpiperazino.
• R 5 is a PEG-containing linking group and R 2 can be H or can have the same definition as above for R 5 for embodiment (1)
• Suitable linking groups are well known in the art and include disulfide groups, thioether groups, acid labile groups, photolabile groups, peptidase labile groups and esterase labile groups. Preferred are disulfide groups and thioether groups.
• the side chain carrying the thiol or disulfide group can be linear or branched, aromatic or heterocyclic.
• the taxane is linked to the polyethylene glycol through the hydroxyl group on the taxane.
• the hydroxyl group is used to form, for example, an ether, ester, or carbamate to link to one end of the polyethylene glycol.
• the moiety that contains the thiol- or disulfide group is linked to the other end of the polyethylene glycol.
• This linking moiety will contain, for example, an ether, ester, amide or carbamate.
• suitable side chains Specific examples of the thiol- or disulfide- containing side chains include:
• Ri3 M ⁇ (OCH 2 C ⁇ 2) 1 ,0(C R,3Ri4) ⁇ (CH2) r dilemma(CR,3Ri4) ⁇ SZ, -CO(C R 13 R 14 ),(CH 2 ) m (C R13R14).
• X is a linear alkyl or branched alkyl having 1-10 carbon atoms
• R and R 12 are the same or different and represent linear alkyl, branched alkyl or cyclic alkyl having 1 to 10 carbon atoms, or simple or substituted aryl or heterocyclic, and R 12 can in addition be H, [38] R ⁇ 3 and R 14 are same or different and represent H or linear alkyl, branched alkyl or cyclic alkyl having 1 to 10 carbon atoms, or simple or substituted aryl, [39] 1 is 0 or an integer from 1 to 10,
• m is an integer of 1 to 10
• n 2 to 1000.
• Examples of linear alkyls include methyl, ethyl, propyl, butyl, pentyl and hexyl.
• Examples of branched alkyls include isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl and 1-ethyl-propyl.
• Examples of cyclic alkyls include cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.
• Examples of simple aryls include phenyl and naphthyl.
• substituted aryls include aryls such as those described above substituted with alkyl groups, with halogens, such as CI, Br, F, nitro groups, amino groups, sulfonic acid groups, carboxylic acid groups, hydroxy groups or alkoxy groups.
• heterocyclics are compounds wherein the heteroatoms are selected from O, N, and S, and include morpholino, piperidino, piperazino, N- methylpiperazino, pyrrollyl, pyridyl, furyl and thiophene.
• the taxanes of the present invention that have a PEG-containing thiol- or disulfide-containing substituent are in themselves novel.
• the taxanes that have a PEG-containing thiol or disulfide-containing substituent can be synthesized according to known methods.
• the starting material for the synthesis is the commercially available 10-deacetylbaccatin III, shown in Figure 3.
• the chemistry to introduce various substituents is described in several publications (Ojima et al, J.Med. Chem.39, 3889-3896, (1996), Ojima et al., 40 J. Med. Chem. 267-278 (1997); I. Ojima et al., 96 Proc. Natl. Acad. Set, 4256-4261 (1999); I. Ojima et al., USP 5,475,011 and USP 5,811,452).
• the substituent Ri on the phenyl ring and the position of the substituent Ri can be varied until a compound of the desired toxicity is obtained. Furthermore, the degree of substitution on the phenyl ring can be varied to achieve a desired toxicity. That is, the phenyl ring can have one or more substituents (e.g., mono-, di-, or tri- substitution of the phenyl ring) which provide another means for achieving a desired toxicity.
• High cytotoxicity is defined as exhibiting a toxicity having an IC 50 in the range of 1 x 10 "12 to 3 x 10 "9 M, when measured in vitro with cultured cancer cells upon a 72 hour exposure time to the drug.
• One of ordinary skill in the art can determine the appropriate chemical moiety for Rj and the appropriate position for Ri using only routine experimentation.
• the disulfide or thiol-containing substituent can be incorporated into the PEG group that is introduced by reaction at the one of the hydroxyl substituents in the taxane skeleton.
• the chemistry to protect the various hydroxyl groups, while reacting the desired one, has been described previously (see, for example, the references cited supra).
• the substituent is introduced by simply converting the free hydroxyl group to a PEG-containing ether, a PEG-containing ester, or a PEG-containing carbamate. This transformation is achieved as follows.
• the desired hydroxyl group is deprotonated by treatment with the commercially available reagent lithium hexamethyldisilazane (1.2 equivalents) in tetrahydrofuran at -40°C as described in I. Ojima et al, supra.
• the resulting alkoxide anion is then reacted with halogenated PEG bearing an appropriately protected thiol substituent, followed by deprotection of the thiol group to provide the desired thiol-containing PEGylated taxane.
• the thiol group can be converted into a methyl or pyridyl disulfide by reaction with methyl methane thiolsulfonate or dithiodipyridine respectively. This method is described in USP 5,416,064.
• the desired hydroxyl group can be esterified directly by reaction with a carboxy-PEG bearing a disulfide-containing substituent, in the presence of a coupling agent such as di-isopropylcarbodiimide (DIC), to provide a disulfide-containing PEGylated taxane ester. Reduction of the disulfide substituent can then provide the thiol-containing PEGylated taxane ester.
• a commercially available chloroformate such as para-nitrophenyl chloroformate
• Representative synthetic schemes are shown in Figures 4 to 8 and the methods are described in Example 2.
• Disulfide-containing and thiol-containing PEGylated taxane drugs of the invention can be evaluated for their ability to suppress proliferation of various unwanted cell lines in vitro.
• cell lines such as the human lung carcinoma line A549, the human breast tumor line MCF-7, and the Burkitt's lymphoma line Namalwa can easily be used for the assessment of cytotoxicity of these compounds.
• Cells to be evaluated can be exposed to the compounds for 72 hours and the surviving fractions of cells measured in direct assays by known methods. IC 50 values can then be calculated from the results of the assays. Results from the testing of PEGylated taxoids of this invention are shown in Figures 9, 10, and 11.
• PEGylated taxoid 17 is extremely potent with an IC 50 value of 6.3 x 10 "1 ' M towards MCF-7 cells.
• Pegylated taxoid 20 is also highly potent, with an IC 50 value of 3.2 x 10 '10 M towards MCF-7 cells.
• Cell binding agents may be of any kind presently known, or that become known and include peptides and non-peptides.
• the cell-binding agent may be any compound that can bind a cell, either in a specific or nonspecific manner. Generally, these can be antibodies, or fragments thereof (especially monoclonal antibodies), lymphokines, hormones, growth factors, vitamins, nutrient-transport molecules (such as transferrin), or any other cell binding molecule or substance.
• cell binding agents that can be used include:
• -interferons e.g. ⁇ , ⁇ , ⁇
• -lymphokines such as IL-2, IL-3, IL-4, IL-6;
• -hormones such as insulin, TRH (thyrotropin releasing hormones), MSH (melanocyte-stimulating hormone), steroid hormones, such as androgens and estrogens;
• -vitamins such as folic acid
• EGF EGF
• TGF- ⁇ TGF- ⁇
• VEGF vascular endothelial growth factor
• PDGF PDGF, FGF, IGF-1, IGF-2, Somatostatin, G-CSF, M-CSF and GM-CSF (Burgess, 5 Immunology Today 155-158 (1984)); and
• Monoclonal antibody techniques allow for the production of extremely specific cell binding agents in the form of specific monoclonal antibodies or fragments thereof.
• Particularly well known in the art are techniques for creating monoclonal antibodies, or fragments thereof, by immunizing mice, rats, hamsters, or any other mammal with the antigen of interest such as the intact target cell, antigens isolated from the target cell, whole virus, attenuated whole virus, and viral proteins such as viral coat proteins.
• Sensitized human cells can also be used.
• Another method of creating monoclonal antibodies, or fragments thereof is the use of phage libraries of sFv (single chain variable region), specifically human sFv. (See e.g., Griffiths et al., USP 5,885,793; McCafferty et al., WO 92/01047; Liming et al., WO 99/06587).
• the monoclonal antibody MY9 is a murine IgGi antibody that binds specifically to the CD33 Antigen (J.D. Griffin et al 8 Leukemia Res., 521 (1984)) and can be used if the target cells express CD33 such as in the disease of acute myelogenous leukemia (AML).
• the monoclonal antibody anti-B4 is a murine IgGi, that binds to the CD 19 antigen on B cells (Nadler et al, 131 J. Immunol.
• the target cells are B cells or diseased cells that express this antigen, such as in non-Hodgkin's lymphoma or chronic lymphoblastic leukemia.
• the antibody N901 is a murine monoclonal IgGi antibody that binds to CD56 found on small cell lung carcinoma cells and on cells of other tumors of neuroendocrine origin (Roy et al. J. Nat. Cancerlnst. 88:1136-1145 (1996)).
• GM-CSF which binds to myeloid cells
• IL-2 which binds to activated T-cells can be used for prevention of transplant graft rejection, for therapy and prevention of graft- versus-host disease, and for treatment of acute T-cell leukemia.
• MSH which binds to melanocytes, can be used for the treatment of melanoma.
• Folic acid which targets the folate receptor expressed on ovarian and other cancers, is also a suitable cell binding agent.
• Cancers of the breast and testes can be successfully targeted with estrogen (or estrogen analogues) or androgen (or androgen analogues), respectively, as cell binding agents.
• Conjugates of the PEGylated taxanes of the invention and a cell binding agent can be formed using any techniques presently known or later developed. Numerous methods of conjugation are taught in USP 5,416,064 and USP 5,475,092.
• the PEGylated taxane ester can be modified to yield a free amino group and then linked to an antibody or other cell binding agent via an acid labile linker or a photolabile linker.
• the PEGylated taxane ester can be condensed with a peptide and subsequently linked to a cell binding agent to produce a peptidase labile linker.
• the hydroxyl group on the PEGylated taxane ester can be succinylated and linked to a cell binding agent to produce a conjugate that can be cleaved by intracellular esterases to liberate free drug.
• the PEGylated taxane ethers, esters, or carbamates are treated to create a free or protected thiol group, and then the disulfide- or thiol-containing taxanes are linked to the cell binding agent via disulfide bonds.
• conjugates of the invention are antibody-PEGylated-taxane, antibody fragment-PEGylated-taxane, epidermal growth factor (EGF)-PEGylated-
• taxane melanocyte stimulating hormone (MSH)-PEGylated-taxane, (IGF-1)- PEGylated-taxane, (IGF-2)-PEGylated-taxane, (Somatostatin)-PEGylated-taxane, thyroid stimulating hormone (TSH)-PEGylated-taxane, estrogen-PEGylated-taxane, estrogen analogue-PEGylated-taxane, androgen-PEGylated-taxane, androgen analogue-PEGylated-taxane, and folate-PEGylated-taxane.
• PEGylated-taxane conjugates of antibodies, antibody fragments, protein or peptide hormones, protein or peptide growth factors and other proteins are made in the same way by known methods.
• peptides and antibodies can be modified with cross linking reagents such as N-succinimidyl 3-(2- pyridyldithio)propionate (SPDP), N-succinimidyl 4-(2-pyridyldithio)pentanoate
• SPP 4-succinimidyl-oxycarbonyl- ⁇ -methyl- ⁇ -(2-pyridyl dithio)-toluene
• SDPB ⁇ -succinimidyl-3-(2-pyridyldithio) butyrate
• 2-iminothiolane or S-acetylsuccinic anhydride by known methods. See, Carlsson et al, 173 Biochem. J. 723-737 (1978); Blattler et al, 24 Biochem. 1517-1524 (1985); Lambert et al, 22 Biochem. 3913-3920 (1983); Klotz et al, 96 Arch. Biochem. Biophys. 605 (1962); and Liu et al, 18 Biochem.
• the free or protected thiol-containing cell binding agent thus derived is then reacted with a disulfide- or thiol-containing taxane to produce conjugates.
• the conjugates can be purified by HPLC or by gel filtration.
• estrogen and androgen cell binding agents such as estradiol and androstenediol can be esterified at the C-17 hydroxy group with an appropriate disulfide containing carboxylic acid using e.g., dicyclohexylcarbodiimide as a condensing agent.
• carboxylic acids that can be employed are 3-(2-pyridyldithio) propanoic acid, 3-methyldithiopropanoic acid, 4-(2-pyridyldithio) pentanoic acid, and 3-phenyldithiopropanoic acid.
• Esterification of the C-17 hydroxy group can also be achieved by reaction with an appropriately protected thiol group containing carboxylic acid chloride such as 3-S-acetylpropanoyl chloride. Other methods of esterification can also be employed as described in the literature (Haslam, 36 Tetrahedron 2409-2433 (1980)).
• the protected or free thiol containing androgen or estrogen can then be reacted with a disulfide- or thiol-containing PEGylated taxane to produce conjugates.
• the conjugates can be purified by column chromatography on silica gel or by HPLC.
• Folic acid can be condensed with a suitable hydrazide such as 4-(2-pyridyldithio) pentanoic acid hydrazide in the presence of a condensing agent such as dicyclohexyl carbodiimide to give a hydrazone containing an active disulfide.
• a suitable hydrazide such as 4-(2-pyridyldithio) pentanoic acid hydrazide
• a condensing agent such as dicyclohexyl carbodiimide
• the disulfide-containing folate can then be reacted with a thiol-containing taxane to produce a conjugate that can be purified by column chromatography over silica gel or by HPLC
• monoclonal antibody- or cell binding agent-PEGylated-taxane conjugates are those that are joined via a disulfide bond, as discussed above, that are capable of delivering the PEGylated taxane molecules.
• Such cell binding conjugates are prepared by known methods such as by modifying monoclonal antibodies with succinimidyl pyridyl-dithiopropionate (SPDP) (Carlsson et al, 173 Biochem. J. 723- 737 (1978)). The resulting thiopyridyl group is then displaced by treatment with thiol-containing PEGylated taxanes to produce disulfide linked conjugates.
• SPDP succinimidyl pyridyl-dithiopropionate
• the formation of the cell binding conjugate is effected by direct displacement of the aryl-thiol of the PEGylated taxane by sulfhydryl groups previously introduced into antibody molecules.
• Conjugates containing 1 to 10 taxane drugs linked via a disulfide bridge are readily prepared by either method.
• a solution of the dithiopyridyl modified antibody at a concentration of 1 mg/ml in 0.1 M potassium phosphate buffer, at pH 6.5 containing 1 mM EDTA is treated with the thiol-containing PEGylated taxane (1.7 molar eq./ dithiopyridyl group).
• the release of thiopyridine from the modified antibody is monitored spectrophotometrically at 343 nm and is complete in about 20 hours.
• the antibody-taxane conjugate is purified and freed of unreacted drug and other low molecular weight material by gel filtration through a column of Sephadex G-25 or Sephacryl S300.
• the number of taxane moieties bound per antibody molecule can be determined by measuring the ratio of the absorbance at 230 nm and 275 nm. An average of 1-10 taxane molecules/antibody molecule can be linked via disulfide bonds by this method.
• Antibody-PEGylated taxane conjugates with non-cleavable links can also be prepared.
• the antibody can be modified with crosslinking reagents such as succinimidyl 4-(maleimidomethyl)cyclohexane-l-carboxylate (SMCC), sulfo-SMCC, m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), sulfo-MBS or succinimidyl-iodoacetate, as described in the literature, to introduce 1-10 reactive groups.
• crosslinking reagents such as succinimidyl 4-(maleimidomethyl)cyclohexane-l-carboxylate (SMCC), sulfo-SMCC, m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), sulfo-MBS or succinimidyl-iodoacetate, as described in the literature, to introduce 1-10 reactive groups.
• the modified antibody is then reacted with the thiol-containing taxane derivative to produce a conjugate.
• the conjugate can be purified by dialysis, or by gel filtration through a Sephadex G-25 or Sephacryl S-300 column.
• the modified antibodies, or fragments thereof, are treated with the thiol-containing PEGylated taxanes (1.25 molar equivalent/maleimido group). The mixtures are incubated overnight at ambient temperature.
• the antibody-taxane conjugates are purified by dialysis, or by gel filtration through a Sephadex G-25 or Sephacryl S-300 column. Typically, an average of 1 to 10 taxanes per antibody are linked.
• a prefe ⁇ ed method is to modify antibodies, or fragments thereof, with succinimidyl-4-(maleimidomethyl)-cyclohexane-l-carboxylate (SMCC) to introduce maleimido groups followed by reaction of the modified antibody or fragment with the thiol-containing PEGylated taxanes to give a thioether linked conjugate.
• SMCC succinimidyl-4-(maleimidomethyl)-cyclohexane-l-carboxylate
• Cytotoxicity of the PEGylated taxanes and their antibody conjugates to non- adherent cell lines can be measured by back- extrapolation of cell proliferation curves as described in Goldmacher et al, 135 J. Immunol. 3648-3651 (1985). Cytotoxicity of these compounds to adherent cell lines such as SKBR3 and A431 can be determined by clonogenic assays as described in Goldmacher et al, 102 J. Cell Biol. 1312-1319 (1986).
• the present invention also provides a therapeutic composition comprising:
• the present invention provides a method of killing selected cell populations comprising contacting the target cells or tissue containing target cells with a cytotoxic amount of the above-described cytotoxic agent.
• cytotoxic agent is prepared as described above.
• Suitable pharmaceutically acceptable carriers, diluents, and excipients are well known and can be determined by those of ordinary skill in the art as the clinical situation warrants.
• suitable carriers, diluents and/or excipients include: (1 )
• the method for killing selected cell populations can be practiced in vitro, in vivo, or ex vivo.
• Examples of in vitro uses include treatments of autologous bone marrow prior to their transplant into the same patient in order to kill diseased or malignant cells; treatments of bone ma ⁇ ow prior to their transplantation in order to kill competent T cells and prevent graft- versus-host-disease (GVHD); treatments of cell cultures in order to kill all cells except for desired variants that do not express the target antigen or to kill variants that express undesired antigen.
• GVHD graft- versus-host-disease
• Examples of clinical ex vivo use are to remove tumor cells or lymphoid cells from bone marrow prior to autologous transplantation in cancer treatment or in treatment of autoimmune disease, or to remove T cells and other lymphoid cells from autologous or allogenic bone marrow or tissue prior to transplant in order to prevent GVHD.
• Treatment can be carried out as follows. Bone marrow is harvested from the patient or other individual and then incubated in medium containing serum to which is
• concentrations range from about 10 ⁇ M to 1 pM, for about 30 minutes to about 48 hours at about 37°C.
• concentration and time of incubation i.e., the dose, are readily determined by one of ordinary skill in the art.
• the bone marrow cells are washed with medium containing serum and returned to the patient intravenously according to known methods.
• the treated marrow cells are stored frozen in liquid nitrogen using standard medical equipment.
• the cytotoxic agent of the invention will be supplied as a solution or a lyophihzed powder that are tested for sterility and for endotoxin levels.
• suitable protocols of conjugate administration are as follows. Conjugates are given weekly for 4 weeks as an intravenous bolus each week. Bolus doses are given in 50 to 100 ml of normal saline to which 5 to 10 ml of human serum
• albumin can be added. Dosages will be 10 ⁇ g to 2000 mg per administration,
• intravenously range of 100 ng to 20mg/kg per day. After four weeks of treatment, the patient can continue to receive treatment on a weekly basis.
• Specific clinical protocols with regard to route of administration, excipients, diluents, dosages, times, etc., can be determined by one of ordinary skill in the art as the clinical situation warrants.
• Examples of medical conditions that can be treated according to the in vivo or ex vivo methods of killing selected cell populations include malignancy of any type including, for example, cancer of the lung, breast, colon, prostate, kidney, pancreas, ovary, and lymphatic organs; autoimmune diseases, such as systemic lupus, rheumatoid arthritis, and multiple sclerosis; graft rejections, such as renal transplant rejection, liver transplant rejection, lung transplant rejection, cardiac transplant rejection, and bone marrow transplant rejection; graft versus host disease; viral infections, such as CMV infection, HIV infection, AIDS, etc.; and parasite infections, such as giardiasis, amoebiasis, schistosomiasis, and others as determined by one of ordinary skill in the art.
• EXAMPLE 1 IN VITRO CYTOTOXICITY ASSAYS [86]
• the sulfide, disulfide, and sulfhydryl containing PEGylated taxane drugs of the invention can be evaluated for their ability to suppress proliferation of various human tumor cell lines in vitro.
• Namalwa (Burkitt's lymphoma) are used for the assessment of cytotoxicity of these compounds. Cells are exposed to the compounds for 72 hours and the surviving fractions of cells are measured in direct assays. (A549 and MCF-7 are assayed for plating efficiency (Goldmacher et al, 102 J. Cell. Biol. 1312-1319 (1986) and
• Namalwa are assayed by growth back extrapolation (Goldmacher et al, 135 J.
• Tetrahydrofuran was dried by distillation over sodium metal.
• Dimethylactamide and dimethylformamide were dried by distillation over calcium hydride under reduced pressure. All other solvents used were reagent grade or HPLC grade.
• the reaction was diluted with 10 mL of 20% ethyl acetate in hexane and passed through a short pad of silica gel using 200 mL of the same solution to wash the silica, and the resulting filtrate was concentrated.
• the crude residue obtained was purified on a silica gel column using 40% ethyl acetate in hexane as the eluant to give 4 as a white solid, which contained small amounts of DCC and acid.
• the product was used without further purification. A small sample was purified the
• Disulfide Links The conjugation of thiol-containing PEGylated taxanes to antibodies, or fragments thereof, via disulfide links is performed in two steps.
• dithiopyridyl groups are introduced into antibodies or antibody fragments using succinimidyl pyridyldithiopentanoate (SPP) as described by Carlsson et al.
• SPP succinimidyl pyridyldithiopentanoate
• the thiopyridyl groups are then displaced by reaction with the thiol-containing taxane to produce a conjugate.
• the release of thiopyridine from the modified antibody or fragment thereof is monitored spectrophotometrically at 343 nm and is found to be complete in about 20 hours.
• the antibody-taxane conjugate is purified and freed of unreacted drug and other low molecular weight material by gel filtration through a column of Sephadex G-25.
• the number of taxane molecules bound per antibody molecule is determined by measuring the ratio between the absorbances at 230 nm and 275 nm. An average of 1-10 taxane molecules per antibody molecule can be linked via disulfide bonds by this method.
• Noncleavable Thioether Link The conjugation of a thiol-containing PEGylated- taxane is performed in two steps.
• the antibody, or fragment thereof, is first reacted with succinimidyl maleimidomethylcyclohexane carboxylate (SMCC) to introduce maleimido groups.
• SMCC succinimidyl maleimidomethylcyclohexane carboxylate
• the modified antibody is then reacted with the thiol-containing PEGylated taxane forming thioether links.
• Antibodies, anti-B4, MY9, anti-EGF receptor and N901, or fragments thereof, are modified with SMCC as described in the literature. [Ill] The modified antibodies or antibody fragments are treated with thiol-containing taxane (1.25 molar equivalent/maleimido group). The mixtures are
• PEGylated Taxanes can be esterified with N-protected amino acids, such as
• N-tboc-L-alanine in the presence of dicyclohexyl-carbodiimide and dimethylaminopyridine (DMAP) by standard methods described in the chemical literature. Cleavage of the t-boc protecting group with trifluoroacetic acid will give a taxane ester containing a terminal amino group. This amino group containing taxane can be linked to antibodies, or fragments thereof, and other cell binding agents via an acid labile linker as previously described (Bla tler et al, 24 Biochemistry, 1517-1524
• Photolabile Linker [113] The amino group-containing PEGylated taxane derivative described above can be linked to cell binding agents via a photolabile linker as previously described.
• amino group-containing PEGylated taxane described above can also be linked to cell binding agents via peptide spacer linkers. It has been previously shown that short peptide spacers between drugs and macromolecular protein carriers are stable in serum but are readily hydrolyzed by intracellular lysosomal peptidases
• the amino group containing taxane can be condensed with peptides such as Ala-Leu, Leu-Ala-Leu or a dimer of Ala-Leu using condensing agents such as l-[3-(dimethylamino)propyl]-3- ethyl carbodiimide-HCl to give a peptide derivative of the taxane which can then be linked to cell binding agents.
• PEGylated Taxanes can be esterified by reaction of the hydroxyl group with succinic anhydride and then linked to a cell binding agent to produce a conjugate that can be cleaved by intracellular esterases to liberate free drug. (For examples see:

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