FIELD OF THE INVENTION [0002] This invention relates to triphenylmethane derivatives which are inhibitors of the mitotic kinesin KSP and are useful in the treatment of cellular proliferative diseases, for example cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation.

BACKGROUND OF THE INVENTION [0003] Among the therapeutic agents used to treat cancer are the taxanes and vinca alkaloids, which act on microtubules. Microtubules are the primary structural element of the mitotic spindle. The mitotic spindle is responsible for distribution of replicate copies of the genome to each of the two daughter cells that result from cell division. It is presumed that disruption of the mitotic spindle by these drugs results in inhibition of cancer cell division, and induction of cancer cell death. However, microtubules form other types of cellular structures, including tracks for intracellular transport in nerve processes. Because these agents do not specifically target mitotic spindles, they have side effects that limit their usefulness.

[0004] Improvements in the specificity of agents used to treat cancer is of considerable interest because of the therapeutic benefits which would be realized if the side effects associated with the administration of these agents could be reduced.

Traditionally, dramatic improvements in the treatment of cancer are associated with identification of therapeutic agents acting through novel mechanisms. Examples of this include not only the taxanes, but also the camptothecin class of topoisomerase I inhibitors. From both of these perspectives, mitotic kinesins are attractive targets for new anti-cancer agents.

[0005] Mitotic kinesins are enzymes essential for assembly and function of the mitotic spindle, but are not generally part of other microtubule structures, such as in nerve processes. Mitotic kinesins play essential roles during all phases of mitosis. These enzymes are"molecular motors"that transform energy released by hydrolysis of ATP into mechanical force which drives the directional movement of cellular cargoes along microtubules. The catalytic domain sufficient for this task is a compact structure of approximately 340 amino acids. During mitosis, kinesins organize microtubules into the bipolar structure that is the mitotic spindle. Kinesins mediate movement of chromosomes along spindle microtubules, as well as structural changes in the mitotic spindle associated with specific phases of mitosis. Experimental perturbation of mitotic kinesin function causes malformation or dysfunction of the mitotic spindle, frequently resulting in cell cycle arrest and cell death.

[0006] Among the mitotic kinesins which have been identified is KSP. KSP belongs to an evolutionarily conserved kinesin subfamily of plus end-directed microtubule motors that assemble into bipolar homotetramers consisting of antiparallel homodimers. During mitosis KSP associates with microtubules of the mitotic spindle.

Microinjection of antibodies directed against KSP into human cells prevents spindle pole separation during prometaphase, giving rise to monopolar spindles and causing mitotic arrest and induction of programmed cell death. KSP and related kinesins in other, non- human, organisms, bundle antiparallel microtubules and slide them relative to one another, thus forcing the two spindle poles apart. KSP may also mediate in anaphase B spindle elongation and focussing of microtubules at the spindle pole.

[0007] Human KSP (also termed HsEgS) has been described (Blangy, et al., Cell, 83: 1159-69 (1995); Whitehead, et al., Arthritis Rheum., 39: 1635-42 (1996); Galgio et al., J. Cell Biol., 135: 339-414 (1996); Blangy, et al., J Biol. Chem., 272: 19418-24 (1997); Blangy, et al., Cell Motil Cytoskeleton, 40: 174-82 (1998); Whitehead and Rattner, J. Cell Sci., 111: 2551-61 (1998); Kaiser, et al., JBC 274: 18925-31 (1999); GenBank accession numbers: X85137, NM004523 and U37426), and a fragment of the KSP gene (TRIP5) has been described (Lee, et al., Mol Endocrinol., 9: 243-54 (1995); GenBank accession number L40372). Xenopus KSP homologs (Eg5), as well as Drosophila KLP61 F/KRP1 30 have been reported.

[0008] Mitotic kinesins are attractive targets for the discovery and development of novel mitotic chemotherapeutics. Accordingly, it is an object of the present invention to provide methods and compositions useful in the inhibition of KSP, a mitotic kinesin.

[0009] Certain triphenylmethanes have been disclosed as inhibitors of Ca++ activated potassium channels (WO 97/345780), but inhibition of KSP by triphenylmethanes has not been described.

SUMMARY OF THE INVENTION [0010] In accordance with the objects outlined above, the present invention provides compositions and methods that can be used to treat diseases of proliferating cells. The compositions are KSP inhibitors, particularly human KSP inhibitors.

[0011] In one aspect, the invention relates to methods for treating cellular proliferative diseases, for treating disorders associated with KSP kinesin activity, and for inhibiting KSP kinesin. The methods employ compounds of the formula : wherein Rl is hydrogen or lower alkyl ; R2 is chosen from H,-OH,-F,-NH2, and-NO2 ; R3 is chosen from H,-COOH,-O- (alkyl), and-OH; R4 is chosen from H,-OH, and-COO (alkyl) ; R5 is chosen from-S-(alkyl),-NH2,-N (alkyl) 2,-OH,-O-(alkyl) and SO2CH3 ; R6 is chosen from H,-N (alkyl) 2,-OH and-COOH; R7 is chosen from H,-N (alkyl) 2,-OH and-COOH; and R is chosen from-S-(alkyl),-NH2,-N (alkyl) 2,-OH,-O-(alkyl) and S02CH3, wherein at least one of R2, R3 and R4 must be other than hydrogen.

[0012] Diseases and disorders that respond to therapy with compounds of the invention include cancer, hyperplasia, restenosis, cardiac hypertrophy, immune disorders and inflammation.

10013] In another aspect, the invention relates to compounds useful in inhibiting KSP kinesin. The compounds have the structures shown above.

[0014] In an additional aspect, the present invention provides methods of screening for compounds that will bind to a KSP kinesin, for example compounds that will displace or compete with the binding of the compositions of the invention. The methods comprise combining a labeled compound of the invention, a KSP kinesin, and at least one candidate agent and determining the binding of the candidate bioactive agent to the KSP kinesin.

[0015] In a further aspect, the invention provides methods of screening for modulators of KSP kinesin activity. The methods comprise combining a composition of the invention, a KSP kinesin, and at least one candidate agent and determining the effect of the candidate bioactive agent on the KSP kinesin activity.

[0016] In another aspect, the invention relates to novel compounds that show activity in inhibiting KSP kinesin. The compounds have the structures: wherein the substituents are as defined before.

DETAILED DESCRIPTION OF THE INVENTION [0017] The present invention is directed to a class of novel triphenylmethanes that are modulators of mitotic kinesins. By inhibiting or modulating mitotic kinesins, but not other kinesins (e. g., transport kinesins), specific inhibition of cellular proliferation is accomplished. Thus, the present invention capitalizes on the finding that perturbation of mitotic kinesin function causes malformation or dysfunction of mitotic spindles, frequently resulting in cell cycle arrest and cell death. The methods of inhibiting a human KSP lcinesin comprise contacting an inhibitor of the invention with a KSP kinesin, particularly human KSP kinesins, including fragments and variants of KSP. The inhibition can be of the ATP hydrolysis activity of the KSP kinesin and/or the mitotic spindle formation activity, such that the mitotic spindles are disrupted. Meiotic spindles may also be disrupted.

[0018] An object of the present invention is to develop inhibitors and modulators of mitotic kinesins, in particular KSP, for the treatment of disorders associated with cell proliferation. Traditionally, dramatic improvements in the treatment of cancer, one type of cell proliferative disorder, have been associated with identification of therapeutic agents acting through novel mechanisms. Examples of this include not only the taxane class of agents that appear to act on microtubule formation, but also the camptothecin class of topoisomerase I inhibitors. The compositions and methods described herein can differ in their selectivity and are preferably used to treat diseases of proliferating cells, including, but not limited to cancer, hyperplasias, restenosis, cardiac hypertrophy, immune disorders and inflammation.

[0019] Accordingly, the present invention relates to methods employing triphenylmethanes of the formula: [0020] All of the compounds falling within the foregoing parent genus and its subgenera are useful as kinesin inhibitors, but not all the compounds are novel. In particular, certain known species fall within the genus, although no utility in inhibiting kinesin has been suggested for these species. Any narrowing of the claims or specific exceptions that might be added to these claims reflect applicants'intent to avoid claiming subject matter that, while functionally part of the inventive concept, is not patentable to them for reasons having nothing to do with the scope of their invention. In particular, the novel compounds that are the subject of the claims are described by the formulas: when R2 is-OH and R3 and R4 are hydrogen, Rs and R8 cannot be-N (CH3)2.

[0021] Preferred compounds of the methods and compositions are those in which: (1) R2 is chosen from-OH,-F,-NH2, and-N02 ; (2) R2 is H and R3 is-OH,- COOH or-OCH3; (3) Rs and R8 are chosen from-N (alkyl) 2 and-OH; (4) R is chosen from-OH,-F, and-NH2 ; (5) R6 and R7 are hydrogen or R6 and R7 are-N (alkyl) 2; and R5 and R8 are chosen from-S-CH3,-N (lower-alkyl) 2 and SO2CH3.

Definitions [0022] Alkyl is intended to include linear, branched, or cyclic hydrocarbon structures and combinations thereof having 12 or fewer carbons. Lower alkyl refers to alkyl groups of from 1 to 5 carbon atoms. Examples of lower alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, s-and t-butyl and the like. Cycloalkyl is a subset of alkyl and includes cyclic hydrocarbon groups of from 3 to 12 carbon atoms.

Examples of cycloalkyl groups include c-propyl, c-butyl, c-pentyl, norbornyl, adamantyl and the like. When an alkyl residue having a specific number of carbons is named, all geometric isomers having that number of carbons are intended to be encompassed; thus, for example,"butyl"is meant to include n-butyl, sec-butyl, isobutyl and t-butyl; "propyl"includes n-propyl and isopropyl.

[0023] Alkoxy or alkoxyl refers to groups of from 1 to 8 carbon atoms of a straight, branched, cyclic configuration and combinations thereof attached to the parent structure through an oxygen. Examples include methoxy, ethoxy, propoxy, isopropoxy, cyclopropyloxy, cyclohexyloxy and the like. Lower-alkoxy refers to groups containing one to four carbons, and such are preferred.

[0024] Halogen refers to fluorine, chlorine, bromine or iodine. Fluorine, chlorine and bromine are preferred.

[0025] Some of the compounds described herein contain one or more asymmetric centers (e. g. the methine carbon when each of the phenyl rings is differently substituted) and may thus give rise to enantiomers, diastereomers (e. g. when Rl contains a stereogenic center), and other stereoisomeric forms that may be defined, in terms of absolute stereochemistry, as (R)-or (S)-. The present invention is meant to include all such possible isomers, including racemic mixtures, optically pure forms and intermediate mixtures. Optically active (R)-and (S)-isomers may be prepared using chiral synthons or chiral reagents, or resolved using conventional techniques. When the compounds described herein contain olefinic double bonds or other centers of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers. Likewise, all tautomeric forms are also intended to be included.

[0026] When desired, the R-and S-isomers may be resolved by methods known to those skilled in the art, for example by formation of diastereoisomeric salts or complexes which may be separated, for example, by crystallisation; via formation of diastereoisomeric derivatives which may be separated, for example, by crystallisation, gas-liquid or liquid chromatography; selective reaction of one enantiomer with an enantiomer-specific reagent, for example enzymatic oxidation or reduction, followed by separation of the modified and unmodified enantiomers ; or gas-liquid or liquid chromatography in a chiral environment, for example on a chiral support, such as silica with a bound chiral ligand or in the presence of a chiral solvent. It will be appreciated that where the desired enantiomer is converted into another chemical entity by one of the separation procedures described above, a further step may be required to liberate the desired enantiomeric form. Alternatively, specific enantiomer may be synthesized by asymmetric synthesis using optically active reagents, substrates, catalysts or solvents, or by converting one enantiomer to the other by asymmetric transformation.

[0027] The compositions of the invention are synthesized as outlined below, utilizing techniques well known in the art. Once made, the compositions of the invention find use in a variety of applications. As will be appreciated by those in the art, mitosis may be altered in a variety of ways; that is, one can affect mitosis either by increasing or decreasing the activity of a component in the mitotic pathway. Stated differently, mitosis may be affected (e. g., disrupted) by disturbing equilibrium, either by inhibiting or activating certain components. Similar approaches may be used to alter meiosis.

[0028] In a preferred embodiment, the compositions of the invention are used to modulate mitotic spindle formation, thus causing prolonged cell cycle arrest in mitosis.

By"modulate"herein is meant altering mitotic spindle formation, including increasing and decreasing spindle formation. By"mitotic spindle formation"herein is meant organization of microtubules into bipolar structures by mitotic kinesins. By"mitotic spindle dysfunction"herein is meant mitotic arrest and monopolar spindle formation.

[0029] The compositions of the invention are useful to bind to and/or modulate the activity of a mitotic kinesin, KSP. In a preferred embodiment, the KSP is human KSP, although KSP kinesins from other organisms may also be used. In this context, modulate means either increasing or decreasing spindle pole separation, causing malformation, i. e., splaying, of mitotic spindle poles, or otherwise causing morphological perturbation of the mitotic spindle. Also included within the definition of KSP for these purposes are variants and/or fragments of KSP. See U. S. Patent Application"Methods of Screening for Modulators of Cell Proliferation and Methods of Diagnosing Cell Proliferation States", filed Oct. 27,1999 (U. S. Serial Number 09/428,156), hereby incorporated by reference in its entirety. In addition, other mitotic kinesins may be used in the present invention. However, the compositions of the invention have been shown to have specificity for KSP.

[0030] For assay of activity, generally either KSP or a compound according to the invention is non-diffusably bound to an insoluble support having isolated sample receiving areas (e. g., a microtiter plate, an array, etc.). The insoluble support may be made of any composition to which the compositions can be bound, is readily separated from soluble material, and is otherwise compatible with the overall method of screening.

The surface of such supports may be solid or porous and of any convenient shape.

Examples of suitable insoluble supports include microtiter plates, arrays, membranes and beads. These are typically made of glass, plastic (e. g., polystyrene), polysaccharides, nylon or nitrocellulose, Teflon, etc. Microtiter plates and arrays are especially convenient because a large number of assays can be carried out simultaneously, using small amounts of reagents and samples. The particular manner of binding of the composition is not crucial so long as it is compatible with the reagents and overall methods of the invention, maintains the activity of the composition and is nondiffusable.

Preferred methods of binding include the use of antibodies (which do not sterically block either the ligand binding site or activation sequence when the protein is bound to the support), direct binding to"sticky"or ionic supports, chemical crosslinking, the synthesis of the protein or agent on the surface, etc. Following binding of the protein or agent, excess unbound material is removed by washing. The sample receiving areas may then be blocked through incubation with bovine serum albumin (BSA), casein or other innocuous protein or other moiety.

[0031] The antimitotic agents of the invention may be used on their own to modulate the activity of a mitotic kinesin, particularly KSP. In this embodiment, the mitotic agents of the invention are combined with KSP and the activity of KSP is assayed. Kinesin activity is known in the art and includes one or more kinesin activities.

Kinesin activities include the ability to affect ATP hydrolysis; microtubule binding; gliding and polymerization/depolymerization (effects on microtubule dynamics) ; binding to other proteins of the spindle; binding to proteins involved in cell-cycle control; serving as a substrate to other enzymes ; such as kinases or proteases; and specific kinesin cellular activities such as spindle pole separation.

[0032] Methods of performing motility assays are well known to those of skill in the art. (See e. g., Hall, et al. (1996), Biophys. J., 71: 3467-3476, Turner et al., 1996, Anal. Biochem. 242 (1): 20-5; Gittes et al., 1996, Biophys. J. 70 (1) : 418-29; Shirakawa et al., 1995, J. Exp. BioL 198: 1809-15; Winkelmann et al., 1995, Biophys. J. 68: 2444-53; Winkelmann et al., 1995, Biophys. J. 68: 72S.) [0033] Methods known in the art for determining ATPase hydrolysis activity also can be used. Preferably, solution based assays are utilized. U. S. application 09/314,464, filed May 18,1999, hereby incorporated by reference in its entirety, describes such assays. Alternatively, conventional methods are used. For example, Pi release from kinesin can be quantified. In one preferred embodiment, the ATPase hydrolysis activity assay utilizes 0.3 M PCA (perchloric acid) and malachite green reagent (8.27 mM sodium molybdate II, 0.33 mM malachite green oxalate, and 0.8 mM Triton X-1 00). To perform the assay, 10 iL of reaction is quenched in 90 tL of cold 0.3 M PCA. Phosphate standards are used so data can be converted to mM inorganic phosphate released. When all reactions and standards have been quenched in PCA, 100 u, L of malachite green reagent is added to the relevant wells in e. g., a microtiter plate.

The mixture is developed for 10-15 minutes and the plate is read at an absorbance of 650 nm. If phosphate standards were used, absorbance readings can be converted to mM Pi and plotted over time. Additionally, ATPase assays known in the art include the luciferase assay.

[0034] ATPase activity of kinesin motor domains also can be used to monitor the effects of modulating agents. In one embodiment ATPase assays of kinesin are performed in the absence of microtubules. In another embodiment, the ATPase assays are performed in the presence of microtubules. Different types of modulating agents can be detected in the above assays. In a preferred embodiment, the effect of a modulating agent is independent of the concentration of microtubules and ATP. In another embodiment, the effect of the agents on kinesin ATPase can be decreased by increasing the concentrations of ATP, microtubules or both. In yet another embodiment, the effect of the modulating agent is increased by increasing concentrations of ATP, microtubules or both.

[0035] Agents that modulate the biochemical activity of KSP in vitro may then be screened in vivo. Methods for such agents in vivo include assays of cell cycle distribution, cell viability, or the presence, morphology, activity, distribution, or amount of mitotic spindles. Methods for monitoring cell cycle distribution of a cell population, for example, by flow cytometry, are well known to those skilled in the art, as are methods for determining cell viability. See for example, U. S. Patent Application "Methods of Screening for Modulators of Cell Proliferation and Methods of Diagnosing Cell Proliferation States,"filed Oct. 22,1999, serial number 09/428, 156, hereby incorporated by reference in its entirety.

[0036] In addition to the assays described above, microscopic methods for monitoring spindle formation and malformation are well known to those of skill in the art (see, e. g., Whitehead and Rattner (1998), J. Cell Sci. 111: 2551-61 ; Galgio et al, (1996) J. Cell biol., 135: 399-414).

[0037] The compositions of the invention inhibit the KSP kinesin. One measure of inhibition is IC50, defined as the concentration of the composition at which the activity of KSP is decreased by fifty percent. Preferred compositions have ICso's of less than about 1 mM, with preferred embodiments having IC50's of less than about 100 p1M, with more preferred embodiments having ICso's of less than about 10 JM, with particularly preferred embodiments having IC50's of less than about 1 u, M, and especially preferred embodiments having IC50's of less than about 500 nM. Measurement of IC50 is done using an ATPase assay.

[0038] Another measure of inhibition is Ki. For compounds with IC50's less than 1 JM, the Ki or Kd is defined as the dissociation rate constant for the interaction of the triphenylmethane with KSP. Preferred compounds have Ki's of less than about 100 uM, with preferred embodiments having Ki's of less than about 10 uM, and particularly preferred embodiments having Ki's of less than about 1 uM and especially preferred embodiments having Ki's of less than about 500 nM.

[0039] Another measure of inhibition is GI50, defined as the concentration of the compound that results in a decrease in the rate of cell growth by fifty percent. Preferred compounds have GI50's of less than about 1 mM. The level of preferability of embodiments is a function of their GIso : those having GIso's of less than about 20 uM are more preferred; those having GI50's of 10 pM more so; those having GI50 of less than about 1 1M more so; those having GI50's of 500 nM more so. Measurement of GI50 is done using a cell proliferation assay.

[0040] The compositions of the invention are used to treat cellular proliferation diseases. Disease states which can be treated by the methods and compositions provided herein include, but are not limited to, cancer (further discussed below), autoimmune disease, arthritis, graft rejection, inflammatory bowel disease, proliferation induced after medical procedures, including, but not limited to, surgery, angioplasty, and the like. It is appreciated that in some cases the cells may not be in a hyper or hypo proliferation state (abnormal state) and still require treatment. For example, during wound healing, the cells may be proliferating"normally", but proliferation enhancement may be desired.

Similarly, as discussed above, in the agriculture arena, cells may be in a"normal"state, but proliferation modulation may be desired to enhance a crop by directly enhancing growth of a crop, or by inhibiting the growth of a plant or organism which adversely affects the crop. Thus, in one embodiment, the invention herein includes application to cells or individuals afflicted or impending affliction with any one of these disorders or states.

[0041] The compositions and methods provided herein are particularly deemed useful for the treatment of cancer including solid tumors such as skin, breast, brain, cervical carcinomas, testicular carcinomas, etc. More particularly, cancers that may be treated by the compositions and methods of the invention include, but are not limited to: Cardiac: sarcoma (angiosarcoma, fibrosarcoma, rhabdomyosarcoma, liposarcoma), myxoma, rhabdomyoma, fibroma, lipoma and teratoma; Lung: bronchogenic carcinoma (squamous cell, undifferentiated small cell, undifferentiated large cell, adenocarcinoma), alveolar (bronchiolar) carcinoma, bronchial adenoma, sarcoma, lymphoma, chondromatous hamartoma, mesothelioma; Gastrointestinal: esophagus (squamous cell carcinoma, adenocarcinoma, leiomyosarcoma, lymphoma), stomach (carcinoma, lymphoma, leiomyosarcoma), pancreas (ductal adenocarcinoma, insulinoma, glucagonoma, gastrinoma, carcinoid tumors, vipoma), small bowel (adenocarcinoma, lymphoma, carcinoid tumors, Karposi's sarcoma, leiomyoma, hemangioma, lipoma, neurofibroma, fibroma), large bowel (adenocarcinoma, tubular adenoma, villous adenoma, hamartoma, leiomyoma); Genitourinary tract: kidney (adenocarcinoma, Wilm's tumor (nephroblastoma), lymphoma, leukemia), bladder and urethra (squamous cell carcinoma, transitional cell carcinoma, adenocarcinoma), prostate (adenocarcinoma, sarcoma), testis (seminoma, teratoma, embryonal carcinoma, teratocarcinoma, choriocarcinoma, sarcoma, interstitial cell carcinoma, fibroma, fibroadenoma, adenomatoid tumors, lipoma); Liver: hepatoma (hepatocellular carcinoma), cholangiocarcinoma, hepatoblastoma, angiosarcoma, hepatocellular adenoma, hemangioma ; Bone: osteogenic sarcoma (osteosarcoma), fibrosarcoma, malignant fibrous histiocytoma, chondrosarcoma, Ewing's sarcoma, malignant lymphoma (reticulum cell sarcoma), multiple myeloma, malignant giant cell tumor chordoma, osteochronfroma (osteocartilaginous exostoses), benign chondroma, chondroblastoma, chondromyxofibroma, osteoid osteoma and giant cell tumors; Nervous system: skull (osteoma, hemangioma, granuloma, xanthoma, osteitis deformans), meninges (meningioma, meningiosarcoma, gliomatosis), brain (astrocytoma, medulloblastoma, glioma, ependymoma, germinoma (pinealoma), glioblastoma multiform, oligodendroglioma, schwannoma, retinoblastoma, congenital tumors), spinal cord neurofibroma, meningioma, glioma, sarcoma); Gynecological: uterus (endometrial carcinoma), cervix (cervical carcinoma, pre-tumor cervical dysplasia), ovaries (ovarian carcinoma (serous cystadenocarcinoma, mucinous cystadenocarcinoma, unclassified carcinoma), granulosa-thecal cell tumors, Sertoli-Leydig cell tumors, dysgerminoma, malignant teratoma), vulva (squamous cell carcinoma, intraepithelial carcinoma, adenocarcinoma, fibrosarcoma, melanoma), vagina (clear cell carcinoma, squamous cell carcinoma, botryoid sarcoma (embryonal rhabdomyosarcoma), fallopian tubes (carcinoma); Hematologic: blood (myeloid leukemia (acute and chronic), acute lymphoblastic leukemia, chronic lymphocytic leukemia, myeloproliferative diseases, multiple myeloma, myelodysplastic syndrome), Hodgkin's disease, non-Hodgkin's lymphoma (malignant lymphoma); Skin: malignant melanoma, basal cell carcinoma, squamous cell carcinoma, Karposi's sarcoma, moles dysplastic nevi, lipoma, angioma, dermatofibroma, keloids, psoriasis; and Adrenal glands: neuroblastoma. Thus, the term "cancerous cell"as provided herein, includes a cell afflicted by any one of the above identified conditions.

[0042] Accordingly, the compositions of the invention are administered to cells.

By"administered"herein is meant administration of a therapeutically effective dose of the mitotic agents of the invention to a cell either in cell culture or in a patient. By "therapeutically effective dose"herein is meant a dose that produces the effects for which it is administered. The exact dose will depend on the purpose of the treatment, and will be ascertainable by one skilled in the art using known techniques. As is known in the art, adjustments for systemic versus localized delivery, age, body weight, general health, sex, diet, time of administration, drug interaction and the severity of the condition may be necessary, and will be ascertainable with routine experimentation by those skilled in the art. By"cells"herein is meant cells in which mitosis or meiosis can be altered.

[0043] A"patient"for the purposes of the present invention includes both humans and other animals, particularly mammals, and other organisms. Thus the methods are applicable to both human therapy and veterinary applications. In the preferred embodiment the patient is a mammal, and in the most preferred embodiment the patient is human.

[0044] Mitotic agents having the desired pharmacological activity may be administered in a physiologically acceptable carrier to a patient, as described herein.

Depending upon the manner of introduction, the compounds may be formulated in a variety of ways as discussed below. The concentration of therapeutically active compound in the formulation may vary from about 0.1-100 wt. %. The agents may be administered alone or in combination with other treatments, i. e., radiation, or other chemotherapeutic agents.

[0045] In a preferred embodiment, the pharmaceutical compositions are in a water soluble form, such as pharmaceutically acceptable salts, which is meant to include both acid and base addition salts."Pharmaceutically acceptable acid addition salt"refers to those salts that retain the biological effectiveness of the free bases and that are not biologically or otherwise undesirable, formed with inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p- toluenesulfonic acid, salicylic acid and the like."Pharmaceutically acceptable base addition salts"include those derived from inorganic bases such as sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Particularly preferred are the ammonium, potassium, sodium, calcium, and magnesium salts. Salts derived from pharmaceutically acceptable organic non-toxic bases include salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, and ethanolamine.

[0046] The pharmaceutical compositions can be prepared in various forms, such as granules, tablets, pills, suppositories, capsules, suspensions, salves, lotions and the like. Pharmaceutical grade organic or inorganic carriers and/or diluents suitable for oral and topical use can be used to make up compositions containing the therapeutically- active compounds. Diluents known to the art include aqueous media, vegetable and animal oils and fats. Stabilizing agents, wetting and emulsifying agents, salts for varying the osmotic pressure or buffers for securing an adequate pH value, and skin penetration enhancers can be used as auxiliary agents. The pharmaceutical compositions may also include one or more of the following: carrier proteins such as serum albumin; buffers; fillers such as microcrystalline cellulose, lactose, corn and other starches; binding agents; sweeteners and other flavoring agents; coloring agents; and polyethylene glycol.

Additives are well known in the art, and are used in a variety of formulations.

[0047] The administration of the mitotic agents of the present invention can be done in a variety of ways as discussed above, including, but not limited to, orally, subcutaneously, intravenously, intranasally, transdermally, intraperitoneally, intramuscularly, intrapulmonary, vaginally, rectally, or intraocularly. In some instances, for example, in the treatment of wounds and inflammation, the anti-mitotic agents may be directly applied as a solution or spray.

[0048] To employ the compounds of the invention in a method of screening for compounds that bind to KSP kinesin, the KSP is bound to a support, and a compound of the invention (which is a mitotic agent) is added to the assay. Alternatively, the compound of the invention is bound to the support and KSP is added. Classes of compounds among which novel binding agents may be sought include specific antibodies, non-natural binding agents identified in screens of chemical libraries, peptide analogs, etc. Of particular interest are screening assays for candidate agents that have a low toxicity for human cells. A wide variety of assays may be used for this purpose, including labeled in vitro protein-protein binding assays, electrophoretic mobility shift assays, immunoassays for protein binding, functional assays (phosphorylation assays, etc.) and the like.

[0049] The determination of the binding of the mitotic agent to KSP may be done in a number of ways. In a preferred embodiment, the mitotic agent (the compound of the invention) is labeled, for example, with a fluorescent or radioactive moiety and binding determined directly. For example, this may be done by attaching all or a portion of KSP to a solid support, adding a labeled mitotic agent (for example a compound of the invention in which at least one atom has been replaced by a detectable isotope), washing off excess reagent, and determining whether the amount of the label is that present on the solid support. Various blocking and washing steps may be utilized as is known in the art.

[0050] By"labeled"herein is meant that the compound is either directly or indirectly labeled with a label which provides a detectable signal, e. g., radioisotope, fluorescent tag, enzyme, antibodies, particles such as magnetic particles, chemiluminescent tag, or specific binding molecules, etc. Specific binding molecules include pairs, such as biotin and streptavidin, digoxin and antidigoxin etc. For the specific binding members, the complementary member would normally be labeled with a molecule which provides for detection, in accordance with known procedures, as outlined above. The label can directly or indirectly provide a detectable signal.

[0051] In some embodiments, only one of the components is labeled. For example, the kinesin proteins may be labeled at tyrosine positions using 125I, or with fluorophores. Alternatively, more than one component may be labeled with different labels ; using 1251 for the proteins, for example, and a fluorophor for the mitotic agents.

[0052] The compounds of the invention may also be used as competitors to screen for additional drug candidates."Candidate bioactive agent"or"drug candidate" or grammatical equivalents as used herein describe any molecule, e. g., protein, oligopeptide, small organic molecule, polysaccharide, polynucleotide, etc., to be tested for bioactivity. They may be capable of directly or indirectly altering the cellular proliferation phenotype or the expression of a cellular proliferation sequence, including both nucleic acid sequences and protein sequences. In other cases, alteration of cellular proliferation protein binding and/or activity is screened. Screens of this sort may be performed either in the presence or absence of microtubules. In the case where protein binding or activity is screened, preferred embodiments exclude molecules already known to bind to that particular protein, for example, polymer structures such as microtubules, and energy sources such as ATP. Preferred embodiments of assays herein include candidate agents which do not bind the cellular proliferation protein in its endogenous native state termed herein as"exogenous"agents. In another preferred embodiment, exogenous agents further exclude antibodies to KSP.

[0053] Candidate agents can encompass numerous chemical classes, though typically they are organic molecules, preferably small organic compounds having a molecular weight of more than 100 and less than about 2,500 daltons. Candidate agents comprise functional groups necessary for structural interaction with proteins, particularly hydrogen bonding and lipophilic binding, and typically include at least an amine, carbonyl, hydroxyl, ether, or carboxyl group, preferably at least two of the functional chemical groups. The candidate agents often comprise cyclical carbon or heterocyclic structures and/or aromatic or polyaromatic structures substituted with one or more of the above functional groups. Candidate agents are also found among biomolecules including peptides, saccharides, fatty acids, steroids, purines, pyrimidines, derivatives, structural analogs or combinations thereof. Particularly preferred are peptides.

[0054] Candidate agents are obtained from a wide variety of sources including libraries of synthetic or natural compounds. For example, numerous means are available for random and directed synthesis of a wide variety of organic compounds and biomolecules, including expression of randomized oligonucleotides. Alternatively, libraries of natural compounds in the form of bacterial, fungal, plant and animal extracts are available or readily produced. Additionally, natural or synthetically produced libraries and compounds are readily modified through conventional chemical, physical and biochemical means. Known pharmacological agents may be subjected to directed or random chemical modifications, such as acylation, alkylation, esterification, amidification to produce structural analogs.

[0055] Competitive screening assays may be done by combining KSP and a drug candidate in a first sample. A second sample comprises a mitotic agent, KSP and a drug candidate. This may be performed in either the presence or absence of microtubules.

The binding of the drug candidate is determined for both samples, and a change, or difference in binding between the two samples indicates the presence of an agent capable of binding to KSP and potentially modulating its activity. That is, if the binding of the drug candidate is different in the second sample relative to the first sample, the drug candidate is capable of binding to KSP.

[0056] In a preferred embodiment, the binding of the candidate agent is determined through the use of competitive binding assays. In this embodiment, the competitor is a binding moiety known to bind to KSP, such as an antibody, peptide, binding partner, ligand, etc. Under certain circumstances, there may be competitive binding as between the candidate agent and the binding moiety, with the binding moiety displacing the candidate agent.

[0057] In one embodiment, the candidate agent is labeled. Either the candidate agent, or the competitor, or both, is added first to KSP for a time sufficient to allow binding, if present. Incubations may be performed at any temperature which facilitates optimal activity, typically between 4 and 40°C.

[0058] Incubation periods are selected for optimum activity, but may also be optimized to facilitate rapid high throughput screening. Typically between 0.1 and 1 hour will be sufficient. Excess reagent is generally removed or washed away. The second component is then added, and the presence or absence of the labeled component is followed, to indicate binding.

[0059] In a preferred embodiment, the competitor is added first, followed by the candidate agent. Displacement of the competitor is an indication the candidate agent is binding to KSP and thus is capable of binding to, and potentially modulating, the activity of KSP. In this embodiment, either component can be labeled. Thus, for example, if the competitor is labeled, the presence of label in the wash solution indicates displacement by the agent. Alternatively, if the candidate agent is labeled, the presence of the label on the support indicates displacement.

[0060] In an alternative embodiment, the candidate agent is added first, with incubation and washing, followed by the competitor. The absence of binding by the competitor may indicate the candidate agent is bound to KSP with a higher affinity.

Thus, if the candidate agent is labeled, the presence of the label on the support, coupled with a lack of competitor binding, may indicate the candidate agent is capable of binding to KSP.

[0061] It may be of value to identify the binding site of KSP. This can be done in a variety of ways. In one embodiment, once KSP has been identified as binding to the mitotic agent, KSP is fragmented or modified and the assays repeated to identify the necessary components for binding.

[0062] Modulation is tested by screening for candidate agents capable of modulating the activity of KSP comprising the steps of combining a candidate agent with KSP, as above, and determining an alteration in the biological activity of KSP. Thus, in this embodiment, the candidate agent should both bind to KSP (although this may not be necessary), and alter its biological or biochemical activity as defined herein. The methods include both in vitro screening methods and in vivo screening of cells for alterations in cell cycle distribution, cell viability, or for the presence, morpohology, activity, distribution, or amount of mitotic spindles, as are generally outlined above.

[0063] Alternatively, differential screening may be used to identify drug candidates that bind to the native KSP, but cannot bind to modified KSP.

[0064] Positive controls and negative controls may be used in the assays.

Preferably all control and test samples are performed in at least triplicate to obtain statistically significant results. Incubation of all samples is for a time sufficient for the binding of the agent to the protein. Following incubation, all samples are washed free of non-specifically bound material and the amount of bound, generally labeled agent determined. For example, where a radiolabel is employed, the samples may be counted in a scintillation counter to determine the amount of bound compound.

[0065] A variety of other reagents may be included in the screening assays.

These include reagents like salts, neutral proteins, e. g., albumin, detergents, etc which may be used to facilitate optimal protein-protein binding and/or reduce non-specific or background interactions. Also reagents that otherwise improve the efficiency of the assay, such as protease inhibitors, nuclease inhibitors, anti-microbial agents, etc., may be used. The mixture of components may be added in any order that provides for the requisite binding.

[0066] The following examples serve to more fully describe the manner of using the above-described invention, as well as to set forth the best modes contemplated for carrying out various aspects of the invention. It is understood that these examples in no way serve to limit the true scope of this invention, but rather are presented for illustrative purposes. All references cited herein are incorporated by reference in their entirety.

EXAMPLES Abbreviations and Definitions [0067] The following abbreviations and terms have the indicated meanings throughout: Ac = acetyl BNB = 4-bromomethyl-3-nitrobenzoic acid Boc = t-butyloxy carbonyl <BR> <BR> <BR> Bu = butyl<BR> <BR> <BR> <BR> <BR> c-= cyclo CBZ = carbobenzoxy = benzyloxycarbonyl DBU = diazabicyclo [5.4.0] undec-7-ene DCM = dichloromethane = methylene chloride = CH2C12 DCE = dichloroethane DEAD = diethyl azodicarboxylate DIC = diisopropylcarbodiimide DIEA = N, N-diisopropylethylamine DMAP= 4-N, N-dimethylaminopyridine DMF = N, N-dimethylformamide DMSO= dimethyl sulfoxide DVB = 1, 4-divinylbenzene EDCI = 1- (3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride EEDQ = 2-ethoxy-1-ethoxycarbonyl-1, 2-dihydroquinoline Et = ethyl Fmoc = 9-fluorenylmethoxycarbonyl GC = gas chromatography HATU = O-(7-Azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate HMDS= hexamethyldisilazane HOAc = acetic acid HOBt = hydroxybenzotriazole Me = methyl mesyl = methanesulfonyl MOM = methoxymethyl MTBE = methyl t-butyl ether PEG = polyethylene glycol Ph = phenyl PhOH = phenol PfP pentafluorophenol PPTS pyridinium p-toluenesulfonate <BR> <BR> <BR> Py = pyridine<BR> <BR> <BR> <BR> <BR> PyBroP bromo-tris-pyrrolidino-phosphonium hexafluorophosphate rt = room temperature sat=d-saturated s-= secondary t-= tertiary TBDMS = t-butyldimethylsilyl TES = triethylsilane TFA = trifluoroacetic acid THF = tetrahydrofuran TMOF = trimethyl orthoformate <BR> <BR> <BR> TMS = trimethylsilyl<BR> <BR> <BR> <BR> <BR> tosyl = p-toluenesulfonyl<BR> <BR> <BR> <BR> <BR> Trt = triphenylmethyl Synthesis of Compounds [0068] Two general synthetic approaches to the preparation of prototypical triphenylmethanes are shown below. Other triphenylmethanes are made in analogous fashion: Triphenylmethane Synthesis-Procedure A Triphenylmethane Synthesis-Procedure B Triphenylmethane Procedure A: [0069] Dimethylaniline (4 mmol) was combined with benzaldehyde (2 mmol) in water (2 mL) and sulfuric acid (100 L) and heated at 95'C for 48 h. The cooled mixture was washed with DCM (2 x 4ml), neutralized with Na2C03, extracted with DCM (2 x 4 mLl), dried (MgS04) and evaporated affording product (about 1.50 mmol, 75%) Triphenylmethane Procedure B : [0070] Ethyl-3-hydroxy benzoate (7.50 g, 45.2 mmol) was dissolved in anhydrous THF (50 ml) and cooled to 0° C. A 60 % aqueous solution of sodium hydride (1. 81g, 45.18 mmol) was added in small portions and the mixture was stirred for 10 min.

Chloromethylmethyl ether (4.29 ml, 56.5 mmol) was added over 5 min and the mixture was allowed to warm to RT over lh. The mixture was combined with DCM (150mL) and washed with water (3x 150mL), dried (MgS04) and evaporated affording a clear oil (9.62g, 101%) [0071] 4-Bromothioanisole (812 mg, 4.00 mmol) was dissolved in THF (4 mL) and cooled to-78 °C. 1.6M n-butyl lithium (2.50 mL, 4.00 mmol) was added and the mixture was stirred at-78 °C for 30 min. In a second flask, ethylmethoxymethoxy benzoate (410 mg, 2.00 mmol) was dissolved in THF (4 mL), and cooled to-78 °C.

The first mixture was cannulated into the second and allowed to warm to RT over 1 h.

The mixture was dissolved in DCM (10 mL) and washed with saturated ammonium chloride and water, dried (MgS04) and concentrated.

[0072] To stirring TFA (5 mL) at 0° C was added sodium borohydride crystals (-150 mg). After the reaction slowed, a solution of the material from the previous reaction (150 mg, 0.364 mmol) in DCM (2 mL) was added dropwise over 15 min. 2 drops were added at a time until the color faded to white. Sodium borohydride was added periodically to maintain an excess. After complete addition, the mixture was stirred at 0° C for 15 min. The mixture was dissolved in DCM (25 ml), washed with water (3 x 25 mL), dried (MgS04) and concentrated. Preparative TLC eluting with 15% ethyl acetate/hexane afforded a thick syrup (60 mg, 46%).

Induction of Mitotic Arrest in Cell Populations Treated with a Triphenylmethane KSP Inhibitor [0073] FACS analysis to determine cell cycle stage by measuring DNA content was performed as follows. Skov-3 cells (human ovarian cancer) were split 1: 10 for plating in 10cm dishes and grown to subconfluence with RPMI 1640 medium containing 5% fetal bovine serum (FBS). The cells were then treated with either l OnM paclitaxel, the test compound or 0.25% DMSO (vehicle for compounds) for 24 hours. Cells were then rinsed off the plates with PBS containing 5mM EDTA, pelleted, washed once in PBS containing 1% FCS, and then fixed overnight in 85% ethanol at 4°C. Before analysis, the cells were pelleted, washed once, and stained in a solution of 10ttg propidium iodide and 250gg of ribonuclease (RNAse) A per milliliter at 37°C for half an hour. Flow cytometry analysis was performed on a Becton-Dickinson FACScan, and data from 10,000 cells per sample was analyzed with Modfit software.

[0074] The triphenylmethane compounds, as well as the known anti-mitotic agent paclitaxel, caused a shift in the population of cells from a GO/G1 cell cycle stage (2n DNA content) to a G2/M cell cycle stage (4n DNA content). Other compounds of this class were found to have similar effects.

Monopolar Spindle Formation following Application of a Triphenylmethane KSP Inhibitor [00751 To determine the nature of the G2/M accumulation, human tumor cell lines Skov-3 (ovarian), HeLa (cervical), and A549 (lung) were plated in 96-well plates at densities of 4,000 cells per well (SKOV-3 & HeLa) or 8, 000 cells per well (A549), allowed to adhere for 24 hours, and treated with various concentrations of the triphenylmethane compounds for 24 hours. Cells were fixed in 4% formaldehyde and stained with antitubulin antibodies (subsequently recognized using fluorescently-labeled secondary antibody) and Hoechst dye (which stains DNA).

[0076] Visual inspection revealed that the triphenylmethane compounds caused cell cycle arrest in the prometaphase stage of mitosis. DNA was condensed and spindle formation had initiated, but arrested cells uniformly displayed monopolar spindles, indicating that there was an inhibition of spindle pole body separation. Microinjection of anti-KSP antibodies also causes mitotic arrest with arrested cells displaying monopolar spindles.

Inhibition of Cellular Proliferation in Tumor Cell Lines Treated with Triphenylmethane KSP Inhibitors.

[0077) Cells were plated in 96-well plates at densities from 1000-2500 cells/well of a 96-well plate (depending on the cell line) and allowed to adhere/grow for 24 hours.

They were then treated with various concentrations of drug for 48 hours. The time at which compounds are added is considered To. A tetrazolium-based assay using the reagent 3- (4, 5-dimethylthiazol-2-yl)-5- (3-carboxymethoxyphenyl)-2- (4-sulfophenyl)- 2H-tetrazolium (MTS) (I. S> Patent No. 5,185,450) (see Promega product catalog #G3580, CeIlTiter 96fl) AQUeous One Solution Cell Proliferation Assay) was used to determine the number of viable cells at To and the number of cells remaining after 48 hours compound exposure. The number of cells remaining after 48 hours was compared to the number of viable cells at the time of drug addition, allowing for calculation of growth inhibition.

[0078] The growth over 48 hours of cells in control wells that had been treated with vehicle only (0.25% DMSO) is considered 100% growth and the growth of cells in wells with compounds is compared to this. Triphenylmethane KSP inhibitors inhibited cell proliferation in human tumor cell lines of the following tumor types: lung (NCI- H460, A549), breast (MDA-MB-231, MCF-7, MCF-7/ADR-RES), colon (HT29, HCT15), ovarian (SKOV-3, OVCAR-3), leukemia (HL-60 (TB), K-562), central nervous system (SF-268), renal (A498), osteosarcoma (U2-OS), and cervical (HeLa). In addition, a mouse tumor line (B16, melanoma) was also growth-inhibited in the presence of the triphenylmethane compounds.

[0079] A Giso was calculated by plotting the concentration of compound in u. M vs the percentage of cell growth of cell growth in treated wells. The Giso calculated for the compounds is the estimated concentration at which growth is inhibited by 50% compared to control, i. e., the concentration at which: 100 x ((Treated4g-To)/ (Control4g-To)) = 50.

[0080] All concentrations of compounds are tested in duplicate and controls are averaged over 12 wells. A very similar 96-well plate layout and Gi5 () calculation scheme is used by the National Cancer Institute (see Monks, et al., J. NatI. Cancer Inst. 83 : 757- 766 (1991)). However, the method by which the National Cancer Institute quantitates cell number does not use MTS, but instead employs alternative methods.

Calculation Of IC50 : [0081] Measurement of a composition's ICso for KSP activity uses an ATPase assay. The following solutions are used: Solution 1 consists of 3 mM phosphoenolpyruvate potassium salt (Sigma P-7127), 2 mM ATP (Sigma A-3377), 1 mM IDTT (Sigma D-9779), 5 p1M paclitaxel (Sigma T-7402), 10 ppm antifoam 289 (Sigma A-8436), 25 mM Pipes/KOH pH 6.8 (Sigma P6757), 2 mM MgC12 (VWR JT400301), and 1 mM EGTA (Sigma E3889). Solution 2 consists of 1 mM NADH (Sigma N8129), 0.2 mg/ml BSA (Sigma A7906), pyruvate kinase 7U/ml, L-lactate dehydrogenase 10 U/ml (Sigma P0294), 100 nM KSP motor domain, 50 pg/ml microtubules, 1 mM DTT (Sigma D9779), 5 HM paclitaxel (Sigma T-7402), 10 ppm antifoam 289 (Sigma A-8436), 25 mM Pipes/KOH pH 6.8 (Sigma P6757), 2 mM MgC12 (VWR JT4003-01), and 1 mM EGTA (Sigma E3889). Serial dilutions (8-12 two-fold dilutions) of the composition are made in a 96-well microtiter plate (Corning Costar 3695) using Solution 1. Following serial dilution each well has 50 ul of Solution 1. The reaction is started by adding 50 J. l of solution 2 to each well. This may be done with a multichannel pipettor either manually or with automated liquid handling devices.

The microtiter plate is then transferred to a microplate absorbance reader and multiple absorbance readings at 340 nm are taken for each well in a kinetic mode. The observed rate of change, which is proportional to the ATPase rate, is then plotted as a function of the compound concentration. For a standard ICso determination the data acquired is fit by the following four parameter equation using a nonlinear fitting program (e. g., Grafit 4): Range Range + Background dz 1+ X s ICso where y is the observed rate and x the compound concentration.

[0082] The K ; for a compound is determined from the IC50 based on three assumptions. First, only one compound molecule binds to the enzyme and there is no cooperativity. Second, the concentrations of active enzyme and the compound tested are known (i. e., there are no significant amounts of impurities or inactive forms in the preparations). Third, the enzymatic rate of the enzyme-inhibitor complex is zero. The rate (i. e., compound concentration) data are fitted to the equation: where V is the observed rate, Vmax is the rate of the free enzyme, Io is the inhibitor concentration, Eo is the enzyme concentration, and K< is the dissociation constant of the enzyme-inhibitor complex.

[0083] Several representative compounds of the invention were tested as described above and found to exhibit Ki's below 100 pM. Their structures are as shown: [0084] The triphenylmethane compounds inhibit growth in a variety of cell lines, including cell lines (MCF-7/ADR-RES, HCT1 5) that express P-glycoprotein (also known as Multi-drug Resistance, or MDR+), which conveys resistance to other chemotherapeutic drugs, such as pacilitaxel. Therefore, the triphenylmethanes are anti- mitotics that inhibit cell proliferation, and are not subject to resistance by overexpression of MDR+ by drug-resistant tumor lines.

[0085] Compounds of this class were found to inhibit cell proliferation, although GIso values varied. GISO values for the triphenylmethane compounds tested ranged from 200 nM to greater than the highest concentration tested. By this we mean that although most of the compounds that inhibited KSP activity biochemically did inhibit cell proliferation, for some, at the highest concentration tested (generally about 20 1M), cell growth was inhibited less than 50%. Many of the compounds have GI50 values less than 10 D. M, and several have GI50 values less than 1 pM. Anti-proliferative compounds that have been successfully applied in the clinic to treatment of cancer (cancer chemotherapeutics) have GI50's that vary greatly. For example, in A549 cells, paclitaxel GIso is 4 nM, doxorubicin is 63 nM, 5-fluorouracil is 1 pM, and hydroxyurea is 500 jjM (data provided by National Cancer Institute, Developmental Therapeutic Program, http ://dtp. nci. nih. gov/). Therefore, compounds that inhibit cellular proliferation at virtually any concentration may be useful. However, preferably, compounds will have GI50 values of less than 1 mM. More preferably, compounds will have GI50 values of less than 20 µM. Even more preferably, compounds will have GI50 values of less than 10 µM. Further reduction in GI50 values may also be desirable, including compounds with GIso values of less than 1 µM.