WO2014160034A1 - Aldehyde dehydrogenase-1 modulators and methods of use thereof - Google Patents

Abstract

The present disclosure provides compounds that function as inhibitors of cytosolic aldehyde dehydrogenase- 1 (ALDHlAl) activity.

Description

ALDEHYDE DEHYDROGENASE-1 MODULATORS AND METHODS OF USE THEREOF

CROSS-REFERENCE

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 61/781,793, filed March 14, 2013, which application is incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

[0002] This invention was made with Government support under contract AA011147 awarded by the National Institutes of Health. The Government has certain rights in the invention.

INTRODUCTION

[0003] Aldehyde dehydrogenase- 1 (ALDH1A1) is mitochondria nuclear encoded cytosolic enzyme.

ALDH1 Al has been widely recognized as a key biomarker for cancer stem cell (CSC). Strong support for the CSC hypothesis, which proposes that a relatively rare subpopulation of tumor cells have the unique ability to initiate and perpetuate tumor growth has been published in the past decade. These cells, called cancer stem cells or tumor-initiating cells, share various characteristics with embryonic and somatic stem cells including self-renewal and multi-potent differentiation. CSCs may be highly resistant to radiation or chemotherapy; therefore, the development of more effective therapies for cancer requires effective targeting of this cell population. These cells can be identified and isolated using biomarkers such as ALDH1A1.

[0004] ALDHlAl isozymes, such as ALDH1A1, metabolize a wide variety of intracellular aldehydes and can thus provide resistance to reactive oxygen species (ROS)-derived products or alkylating agents such as cyclophosphamide. High ALDHlAl activity has been reported in CSCs from many cancers including breast, lung, liver, colon, pancreas, ovary, head and neck, prostate cancers and some hematologic cancers. In the literature, silencing ALDHlAl by siRNA or shRNA leads to cell cycle arrest, apoptosis, decreased ceil viability in vitro, and reduced tumorigenesis in vivo. Silencing ALDHlAl by siRNA also sensitizes cancer cells to drug- induced cell death. For example, in an in vivo orthotopic mouse model of ovarian cancer, silencing ALDHlAl using nanoliposomal siRNA sensitized both taxane- and platinum-resistant cell lines to chemotherapy, significantly reducing tumor growth in mice compared with chemotherapy alone (74%-90% reduction; P < 0.015). [Landen, C. N. et al. Mo! Cancer Ther. 2010 Dec;9(12):3186-99; Moreb, J. S. et al., Molecular Cancer 2008, 7:87.] [0005] ALDHlAl is not only a biomarker of CSCs, but also an attractive therapeutic target for human cancer,

[0006] Antagonists of ALDHlAl are useful for treating disorders such as cancer. Compounds of the present disclosure are antagonist of ALDHlAl, or inhibitors of ALDHlAl and are described herein.

SUMMARY

[0007] The present disclosure provides compounds that function as inhibitors or antagonists of aldehyde dehydrogenase- 1 (ALDHlAl) activity, pharmaceutical compositions containing them, and methods of preparing these compounds. In one embodiment, the present disclosure relates to a pharmaceutical composition comprising a compound of formula (I) and a cancer

R¹ and R² are each independently selected from hydrogen and C₁-C6 alkyl;

R³ and R⁴ are each independently selected from hydrogen and C₁-C6 alkyl;

each R⁷ is independently selected from halogen, C₁-C6 alkyl, and OCH₃; and

n is 0, 1, 2, 3, 4, or 5;

provided that when one of R¹ and R² is hydrogen and the other is isopropyl,

[0008] In one embodiment, one of R¹ and R² is hydrogen and the other is Ci-C₆ alkyl. In one embodiment, one of R³ and R⁴ is hydrogen and the other is C₁-C6 alkyl. In one embodiment, one of R³ and R⁴ is hydrogen and the other is methyl or ethyl. In one embodiment, n is 0, 1, 2, or 3. In one embodiment, n is 1, 2, or 3. In one embodiment, n is 1. In one embodiment, n is 2. In one embodiment, each R⁷ is C₁-C6 alkyl. In one embodiment, R⁷ is methyl, ethyl, or isopropyl. In one embodiment, each R⁷ is halogen. In one embodiment, R⁷ is fluoro.

[0009] In one embodiment, the present disclosure relates to a pharmaceutical composition comprising a compound selected from Table 1 , or a pharmaceutically acceptable salt, solvate, or prodrug thereof, and a cancer chemotherapeutic agent.

[0010] In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non- proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

[0011] In another embodiment, the proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[0012] In one embodiment, the present disclosure provides a method of treating or preventing cancer comprising administering to a subject a pharmaceutical composition as described herein. In one embodiment, the present disclosure provides a method of treating or preventing cancer comprising administering to a subject a compound as described herein. In one embodiment, the present disclosure provides a method of treating or preventing cancer comprising administering to a subject a compound is selected from Table 1, or a pharmaceutically acceptable salt, solvate, or prodrug thereof.

[0013] In another embodiment, the method as described herein further comprises administering a cancer chemotherapeutic agent. In one embodiment, the chemotherapeutic agent is selected from non- peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor. In one embodiment, the proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony- stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[0014] In one embodiment, the compound and the chemotherapeutic agent are administered

simultaneously, staggered, alternating, or sequentially.

[0015] In one embodiment, the method as described herein further comprises administering ionizing radiation. In one embodiment, the ionizing radiation is administered via external beam radiation therapy or brachytherapy.

[0016] In one embodiment, the present disclosure provides a method of treating or preventing cancer in a subject comprising administering to the subject a first amount of a compound as described herein in a first treatment procedure, and a second amount of radiation in a second treatment procedure wherein, the first and second amounts together comprise a therapeutically effective amount. In one embodiment, the radiation is a radiopharmaceutical agent. In one embodiment, the radiation is an ionizing radiation administered via external beam radiation therapy or brachytherapy.

[0017] In one embodiment, the cancer is selected from solid tumors, skin cancers, myeloma, lymphoma, leukemia, ovarian cancer, lung cancer, brain cancer, pancreatic cancer, prostate cancer, colon cancer, colorectal cancer, breast cancer, liver cancer, kidney cancer, oral cancer, head cancer, neck cancer, throat cancer, and thyroid cancer.

[0018] In another embodiment, the method described herein provides a synergistic effect in the treatment of cancer.

[0019] In one embodiment, the present disclosure relates to a method of increasing the sensitivity of a cancerous cells or cancer stem cells to a chemotherapeutic agent comprising administering to a subject a compound as described herein or a pharmaceutical composition as described herein. In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone-deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor. In one embodiment, the proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen apoptosis receptor agonists, interleukin-2 interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor. [0020] In one embodiment, the compound or pharmaceutical composition is administered by a route selected from topical, intramuscular, intravenous, subcutaneous, and oral. In one embodiment, the compound or pharmaceutical composition is administered to the respiratory tract.

[0021] In one embodiment, the present disclosure provides a use of a pharmaceutical composition as disclosed above for the manufacture of a medicament for treating or preventing cancer.

[0022] In one embodiment, the present disclosure provides a use of a compound of formula (I) for the manufacture of a medicament for treating or preventing cancer.

[0023] In one embodiment, the present disclosure provides a use of a compound selected from Table 1 herein, or a pharmaceutically acceptable salt, solvate, or prodrug thereof for the manufacture of a medicament for treating or preventing cancer.

[0024] In one embodiment, the medicament further comprises a cancer chemotherapeutic agent.

[0025] In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non- proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

[0026] In one embodiment, the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[0027] In one embodiment, the compound and the chemotherapeutic agent are administered

simultaneously, staggered, alternating, or sequentially.

[0028] In one embodiment, the use further comprises administering ionizing radiation.

[0029] In one embodiment, the ionizing radiation is administered via external beam radiation therapy or brachytherapy.

[0030] In one embodiment, the present disclosure provides a use of a first amount of a compound of formula (I) for the manufacture of a medicament for treating or preventing cancer in a first treatment procedure, wherein the use further comprises a second amount of radiation in a second treatment procedure wherein, the first and second amounts together comprise a therapeutically effective amount.

[0031] In one embodiment, the radiation is a radiopharmaceutical agent. [0032] In one embodiment, the radiation is an ionizing radiation administered via external beam radiation therapy or brachytherapy.

[0033] In one embodiment, the cancer is selected from solid tumors, skin cancers, myeloma, lymphoma, leukemia, ovarian cancer, lung cancer, brain cancer, pancreatic cancer, prostate cancer, colon cancer, colorectal cancer, breast cancer, liver cancer, kidney cancer, oral cancer, head cancer, neck cancer, throat cancer, and thyroid cancer.

[0034] In one embodiment, the use provides a synergistic effect in the treatment of cancer.

[0035] In one embodiment, the present disclosure provides a use of a compound of formula (I) or a pharmaceutical composition as disclosed above for the manufacture of a medicament for increasing the sensitivity of cancerous cells or cancer stem cells to a chemotherapeutic agent.

[0036] In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non- proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

[0037] In one embodiment, the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen apoptosis receptor agonists, interleukin-2 interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[0038] In one embodiment, the compound or pharmaceutical composition is administered by a route selected from topical, intramuscular, intravenous, subcutaneous, and oral.

[0039] In one embodiment, the compound or pharmaceutical composition is administered to the

respiratory tract.

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a graph showing the selectivity of Compound 5 against different ALDH isozymes.

[0041] Figure 2A is a graph showing that Compound 5 sensitizes cytotoxic effect of paclitaxel in human multi-drug resistant ovarian NCI/ADR-RES cancer cells.

[0042] Figure 2B is a graph showing that Compound 5 sensitizes cytotoxic effect of paclitaxel in human multi-drug resistant ovarian TOV-21G-RT cancer cells.

[0043] Figure 3A is a graph showing that Compound 5 sensitizes cytotoxic effect of doxorubicin in human multi-drug resistant ovarian NCI/ADR-RES cancer cells. [0044] Figure 3B is a graph showing that Compound 5 sensitizes cytotoxic effect of doxorubicin in human multi-drug resistant ovarian TOV-21G-RT cancer cells.

DETAILED DESCRIPTION

1. Compounds of the Present Disclosure

[0045]

R¹ and R² are each independently selected from hydrogen and Ci-C₆ alkyl;

R³ and R⁴ are each independently selected from hydrogen and C₁-C6 alkyl;

each R⁷ is independently selected from halogen, C₁-C6 alkyl, and OCH₃; and

n is 0, 1, 2, 3, 4, or 5;

provided that when one of R¹ and R² is hydrogen and the other is isopropyl,

[0046] In one embodiment, one of R¹ and R² is hydrogen and the other is Ci-C₆ alkyl. In one

embodiment, one of R¹ and R² is hydrogen and the other is straight-chain Ci-C₆ alkyl or branched C₃-C6 alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain d- C₄ alkyl or branched C3-C4 alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain C₁-C4 alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is branched C3-C4 alkyl. [0047] In one embodiment, one of R³ and R⁴ is hydrogen and the other is Ci-C₆ alkyl. In one embodiment, one of R³ and R⁴ is hydrogen and the other is methyl or ethyl.

[0048] In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain C₁-C4 alkyl; and one of R³ and R⁴ is hydrogen and the other is methyl or ethyl. In one embodiment, one of R¹ and R² is hydrogen and the other is branched C₃-C₄ alkyl; and one of R³ and R⁴ is hydrogen and the other is methyl or ethyl.

[0049] In one embodiment, n is 0, 1, 2, or 3. In one embodiment, n is 1, 2, or 3. In one embodiment, n is 1. In one embodiment, n is 2.

[0050] In one embodiment, each R⁷ is Ci-C₆ alkyl. In one embodiment, each R⁷ is independently methyl, ethyl, or isopropyl. In one embodiment, each R⁷ is halogen. In one embodiment, each R⁷ is independently chloro or fluoro. In one embodiment, R⁷ is chloro. In one embodiment, R⁷ is fluoro. In one embodiment, one or more R⁷ is Ci-C₆ alkyl and one or more R⁷ is halogen. In one embodiment, one or more R⁷ is independently methyl, ethyl, or isopropyl and one or more R⁷ is independently chloro or fluoro. In one embodiment, one or more R⁷ is Ci-C₆ alkyl and one or more R⁷ is OCH₃. In one example, one or more R⁷ is independently methyl, ethyl, or isopropyl and one or more R⁷ is OCH₃. In one embodiment, one or more R⁷ is halogen and one or more R⁷ is OCH₃. In one example, one or more R⁷ is independently chloro or fluoro and one or more R⁷ is OCH₃.

[0051] It will be apparent to one skilled in the art based one the present disclosure that any of the

embodiments described above for each of R¹, R², R³, R⁴, R⁷, and n can be combined in any manner.

[0052] ae:

Representative compounds of the present disclosure include compounds listed in Table 1. Table 1

[0054] The present disclosure further provides assays for identifying inhibitors of ALDHlAl.

[0055] In some embodiments, subjects to be treated are humans. In some embodiments, a human to be treated according to a subject method is one that has the wild type ALDHlAl allele or a mutated/variant ALDHlAl allele, e.g. a mutated/variant ALDHlAl gene with over-expression of the ALDHlAl transcripts/enzyme, or a mutated/variant ALDHlAl gene which encodes a product with higher enzymatic activity of ALDHlAl. [Spence, J. P. et al., Alcohol Clin Exp Res. 2003 Sep;27(9): 1389-94.]

[0056] A compound can be readily ascertained whether it is an ALDHlAl inhibitor or not. Assays for dehydrogenase activity of ALDHlAl are known in the art, and any known assay can be used. Examples of dehydrogenase assays are found in various publications, including, e.g., Russo and Hilton, 1998, Cancer Res. 48:2963-8; Ho et al., 2006, Biochemistry 45:9445-53; Sheikh et al., 1997, J. Biol. Chem. 272:18817-18822; Vallari and Pietruszko, 1984, J. Biol. Chem. 259:4922; and Farres et al., 1994, J. Biol. Chem. 269:13854-13860. The assays generally comprise two parts; one is the preparation of human ALDHlAl recombinant enzyme; and the other is the determination of the enzyme inhibition by a compound in the present disclosure.

[0057] To prepare human ALDHlAl recombinant enzyme, full-length human ALDHlAl cDNA may be synthesized based on published DNA sequence (e.g., GenBank ID: NM_000689). The synthetic gene may be cloned into the Nhel/EcoRI sites of the His-tag vector, pTrcHis, for protein expression. All the vectors are transformed into BL21 E. coli host cells and subjected to 0.5 niM isopropyl β-D-l-thiogalactopyranoside (IPTG) induction for protein expression at 30 °C.

Purifications of the recombinant proteins by affinity nickel columns (e.g., HisTrap, GE Healthy Science, USA) are carried out using standard protocols according to manufacturer's instructions (e.g., Novagen, USA).

[0058] An example of the enzymatic assay is described as follows. The reaction cocktails are added into the wells in a 96-well plate and then put on a shaker for mixing. After 5 minutes of mixing, 2 of recombinant ALDHlAl enzyme is added to each well with DMSO as blank control in the plate. The plate is again put on shaker for another 5 minutes of shaking to enhance bonding between testing compounds and the enzyme. 2μί of 1M acetyladehyde in water is then added to each of wells containing the above reaction mixture. After a short vigorous mixing, the UV plate is fed into a plate reader to measure kinetic optical density (O.D.) at wavelength 340 nm at 25 °C over 4 minutes. Each point of measurement is taken at a time interval of 40 seconds.

[0059] The term "compounds of the present disclosure" refers to a compound according to formula I.

[0060] With respect to the chemical compounds useful in the present disclsoure, the following terms can be applicable:

[0061] The present disclosure is intended to include all isotopes of atoms occurring in the present

compounds. Isotopes include those atoms having the same atomic number but different mass numbers. By way of general example and without limitation, isotopes of hydrogen include tritium and deuterium, and isotopes of carbon include C-13 and C-14. [0062] When any variable (e.g. , Ri) occurs more than one time in any constituent or formula for a compound, its definition at each occurrence is independent of its definition at every other occurrence. Thus, for example, if a group is shown to be substituted with 0-2 Ri moieties, then the group may optionally be substituted with up to two Ri moieties and Ri at each occurrence is selected independently from the definition of R^ Also, combinations of substituents and/or variables are permissible, but only if such combinations result in stable compounds.

[0063] When a bond to a substituent is shown to cross a bond connecting two atoms in a ring, then such substituent may be bonded to any atom in the ring. When a substituent is listed without indicating the atom via which such substituent is bonded to the rest of the compound of a given formula, then such substituent may be bonded via any atom in such substituent. Combinations of substituents and/or variables are permissible, but only if such combinations result in stable compounds.

[0064] Compounds of the present disclosure that contain nitrogens can be converted to N-oxides by treatment with an oxidizing agent (e.g. , 3-chloroperoxybenzoic acid (ra-CPBA) and/or hydrogen peroxides) to afford other compounds of the present disclosure. Thus, all shown and claimed nitrogen-containing compounds are considered, when allowed by valency and structure, to include both the compound as shown and its N-oxide derivative (which can be designated as N— >0 or N⁺-0^"). Furthermore, in other instances, the nitrogens in the compounds of the present disclosure can be converted to N-hydroxy or N-alkoxy compounds. For example, N-hydroxy compounds can be prepared by oxidation of the parent amine by an oxidizing agent such as ra-CPBA. All shown and claimed nitrogen-containing compounds are also considered, when allowed by valency and structure, to cover both the compound as shown and its N-hydroxy (i.e. , N-OH) and N-alkoxy (i.e. , N-OR, wherein R is substituted or unsubstituted Ci_₆ alkyl,

Ci_6 alkenyl, Ci_₆ alkynyl, C₃._i4 carbocycle, or 3-14-membered heterocycle) derivatives.

[0065] When an atom or chemical moiety is followed by a subscripted numeric range (e.g. , Ci- ), the present disclosure is meant to encompass each number within the range as well as all intermediate ranges. For example, "Ci_₆ alkyl" is meant to include alkyl groups with 1, 2, 3, 4, 5, 6, 1-6, 1-5, 1-4, 1-3, 1-2, 2-6, 2-5, 2-4, 2-3, 3-6, 3-5, 3-4, 4-6, 4-5, and 5-6 carbons.

[0066] As used herein, "alkyl" is intended to include both branched and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms. For example, Ci-6 alkyl is intended to include Ci , C2, C3, C4, C5, and Cg alkyl groups. Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, s-pentyl, and n- hexyl. When the term "alkyl" also includes alkyl groups that have oxygen, nitrogen, sulfur or phosphorous atoms replacing one or more hydrocarbon backbone carbon atoms, these are known as heteroalkyl, In certain embodiments, a straight chain or branched chain alkyl has six or fewer carbon atoms in its backbone (e.g. , Ci- for straight chain, C3-C6 for branched chain), and in another embodiment, a straight chain or branched chain alkyl has four or fewer carbon atoms. Likewise, cycloalkyls have from three to eight carbon atoms in their ring structure, and in another embodiment, cycloalkyls have five or six carbons in the ring structure.

[0067] As used herein, "halo" or "halogen" refers to fluoro, chloro, bromo, and iodo. The term

"perhalogenated" generally refers to a moiety wherein all hydrogens are replaced by halogen atoms.

[0068] Additionally, the compounds of the present disclosure, for example, the salts of the compounds, can exist in either hydrated or unhydrated (the anhydrous) form or as solvates with other solvent molecules. Nonlimiting examples of hydrates include monohydrates, dihydrates, etc.

Nonlimiting examples of solvates include ethanol solvates, acetone solvates, etc.

[0069] "Solvates" means solvent addition forms that contain either stoichiometric or non-stoichiometric amounts of solvent. Some compounds have a tendency to trap a fixed molar ratio of solvent molecules in the crystalline solid state, thus forming a solvate. If the solvent is water the solvate formed is a hydrate, when the solvent is alcohol, the solvate formed is an alcoholate. Hydrates are formed by the combination of one or more molecules of water with one of the substances in which the water retains its molecular state as H₂0, such combination being able to form one or more hydrate.

[0070] "Tautomers" refers to compounds whose structures differ markedly in arrangement of atoms, but which exist in easy and rapid equilibrium. It is to be understood that the compounds of the present disclosure may be depicted as different tautomers. It should also be understood that when compounds have tautomeric forms, all tautomeric forms are intended to be within the scope of the present disclosure, and the naming of the compounds does not exclude any tautomer form.

[0071] Some compounds of the present disclosure can exist in a tautomeric form which are also intended to be encompassed within the scope of the present disclosure.

[0072] The compounds, salts and prodrugs of the present disclosure can exist in several tautomeric

forms, including the enol and imine form, and the keto and enamine form and geometric isomers and mixtures thereof. All such tautomeric forms are included within the scope of the present disclosure. Tautomers exist as mixtures of a tautomeric set in solution. In solid form, usually one tautomer predominates. Even though one tautomer may be described, the present disclosure includes all tautomers of the present compounds [0073] A tautomer is one of two or more structural isomers that exist in equilibrium and are readily converted from one isomeric form to another. This reaction results in the formal migration of a hydrogen atom accompanied by a switch of adjacent conjugated double bonds. In solutions where tautomerization is possible, a chemical equilibrium of the tautomers will be reached. The exact ratio of the tautomers depends on several factors, including temperature, solvent, and pH. The concept of tautomers that are interconvertible by tautomerizations is called tautomerism.

[0074] A "pharmaceutical composition" is a formulation containing the disclosed compounds in a form suitable for administration to a subject. In one embodiment, the pharmaceutical composition is in bulk or in unit dosage form. The unit dosage form is any of a variety of forms, including, for example, a capsule, an IV bag, a tablet, a single pump on an aerosol inhaler, or a vial. The quantity of active ingredient (e.g. , a formulation of the disclosed compound or salt, hydrate, solvate, or isomer thereof) in a unit dose of composition is an effective amount and is varied according to the particular treatment involved. One skilled in the art will appreciate that it is sometimes necessary to make routine variations to the dosage depending on the age and condition of the patient. The dosage will also depend on the route of administration. A variety of routes are contemplated, including oral, pulmonary, rectal, parenteral, transdermal, subcutaneous, intravenous, intramuscular, intraperitoneal, inhalational, buccal, sublingual, intrapleural, intrathecal, intranasal, and the like. Dosage forms for the topical or transdermal administration of a compound of this present disclosure include powders, sprays, ointments, pastes, creams, lotions, gels, solutions, patches and inhalants. In one embodiment, the active compound is mixed under sterile conditions with a pharmaceutically acceptable carrier, and with any preservatives, buffers, or propellants that are required.

[0075] A "subject" includes mammals, e.g. , humans, companion animals (e.g. , dogs, cats, birds, and the like), farm animals (e.g. , cows, sheep, pigs, horses, fowl, and the like) and laboratory animals (e.g. , rats, mice, guinea pigs, birds, and the like). In one embodiment, the subject is human.

[0076] As used herein, the phrase "pharmaceutically acceptable" refers to those compounds, materials, compositions, carriers, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio.

[0077] "Pharmaceutically acceptable excipient" means an excipient that is useful in preparing a

pharmaceutical composition that is generally safe, non-toxic and neither biologically nor otherwise undesirable, and includes excipient that is acceptable for veterinary use as well as human pharmaceutical use. A "pharmaceutically acceptable excipient" as used in the specification and claims includes both one and more than one such excipient.

[0078] The compounds of the present disclosure are capable of further forming salts. All of these forms are also contemplated within the scope of the present claims.

[0079] "Pharmaceutically acceptable salt" of a compound means a salt that is pharmaceutically

acceptable and that possesses the desired pharmacological activity of the parent compound.

[0080] As used herein, "pharmaceutically acceptable salts" refer to derivatives of the disclosed

compounds wherein the parent compound is modified by making acid or base salts thereof.

Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines, alkali or organic salts of acidic residues such as carboxylic acids, and the like. The pharmaceutically acceptable salts include the conventional non-toxic salts or the quaternary ammonium salts of the parent compound formed, for example, from non-toxic inorganic or organic acids. For example, such conventional non-toxic salts include, but are not limited to, those derived from inorganic and organic acids selected from 2- acetoxybenzoic, 2-hydroxyethane sulfonic, acetic, ascorbic, benzene sulfonic, benzoic, bicarbonic, carbonic, citric, edetic, ethane disulfonic, 1,2-ethane sulfonic, fumaric, glucoheptonic, gluconic, glutamic, glycolic, glycollyarsanilic, hexylresorcinic, hydrabamic, hydrobromic, hydrochloric, hydroiodic, hydroxy maleic, hydroxynaphthoic, isethionic, lactic, lactobionic, lauryl sulfonic, maleic, malic, mandelic, methane sulfonic, napsylic, nitric, oxalic, pamoic, pantothenic, phenylacetic, phosphoric, polygalacturonic, propionic, salicyclic, stearic, subacetic, succinic, sulfamic, sulfanilic, sulfuric, tannic, tartaric, toluene sulfonic, and the commonly occurring amine acids, e.g. , glycine, alanine, phenylalanine, arginine, etc.

[0081] Other examples include hexanoic acid, cyclopentane propionic acid, pyruvic acid, malonic acid, 3-(4-hydroxybenzoyl)benzoic acid, cinnamic acid, 4-chlorobenzenesulfonic acid, 2- naphthalenesulfonic acid, 4-toluenesulfonic acid, camphorsulfonic acid, 4-methylbicyclo-[2.2.2]- oct-2-ene-l -carboxylic acid, 3-phenylpropionic acid, trimethylacetic acid, tertiary butylacetic acid, muconic acid, and the like. The present disclosure also encompasses salts formed when an acidic proton present in the parent compound either is replaced by a metal ion, e.g., an alkali metal ion, an alkaline earth ion, or an aluminum ion; or coordinates with an organic base such as ethanolamine, diethanolamine, triethanolamine, tromethamine, N-methylglucamine, and the like.

[0082] It should be understood that all references to pharmaceutically acceptable salts include solvent addition forms (solvates) or crystal forms (polymorphs) as defined herein, of the same salt.

[0083] The pharmaceutically acceptable salts of the present disclosure can be synthesized from a parent compound that contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid in water or in an organic solvent, or in a mixture of the two; non-aqueous media like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile can be used. Lists of suitable salts are found in Remington 's Pharmaceutical Sciences, 18th ed. (Mack Publishing Company, 1990). For example, salts can include, but are not limited to, the hydrochloride and acetate salts of the aliphatic amine -containing, hydroxyl amine - containing, and imine -containing compounds of the present disclosure.

[0084] The compounds of the present disclosure can also be prepared as esters, for example

pharmaceutically acceptable esters. For example a carboxylic acid function group in a compound can be converted to its corresponding ester, e.g. , a. methyl, ethyl, or other ester. Also, an alcohol group in a compound can be converted to its corresponding ester, e.g. , an acetate, propionate, or other ester.

[0085] The compounds of the present disclosure can also be prepared as prodrugs, for example

pharmaceutically acceptable prodrugs. The terms "pro-drug" and "prodrug" are used

interchangeably herein and refer to any compound which releases an active parent drug in vivo. Since prodrugs are known to enhance numerous desirable qualities of pharmaceuticals (e.g. , solubility, bioavailability, manufacturing, etc.) the compounds of the present disclosure can be delivered in prodrug form. Thus, the present disclosure is intended to cover prodrugs of the presently claimed compounds, methods of delivering the same and compositions containing the same. "Prodrugs" are intended to include any covalently bonded carriers that release an active parent drug of the present disclosure in vivo when such prodrug is administered to a subject. Prodrugs the present disclosure are prepared by modifying functional groups present in the compound in such a way that the modifications are cleaved, either in routine manipulation or in vivo, to the parent compound. Prodrugs include compounds of the present disclosure wherein a hydroxy, amino, sulfhydryl, carboxy, or carbonyl group is bonded to any group that, may be cleaved in vivo to form a free hydroxyl, free amino, free sulfhydryl, free carboxy or free carbonyl group, respectively.

[0086] Examples of prodrugs include, but are not limited to, esters (e.g. , acetate, dialkylaminoacetates, formates, phosphates, sulfates, and benzoate derivatives) and carbamates (e.g. , N,N- dimethylaminocarbonyl) of hydroxy functional groups, esters groups (e.g. ethyl esters, morpholinoethanol esters) of carboxyl functional groups, N-acyl derivatives (e.g. N-acetyl) N- Mannich bases, Schiff bases and enaminones of amino functional groups, oximes, acetals, ketals and enol esters of ketone and aldehyde functional groups in compounds of Formula I, and the like, See Bundegaard, H. "Design of Prodrugs" p. 1-92, Elesevier, New York-Oxford (1985). [0087] As used herein, the term "mitochondrial aldehyde dehydrogenase- 1" or "ALDHlAl" refers to an enzyme that oxidizes an aldehyde (e.g., a xenogenic aldehyde, a biogenic aldehyde, or an aldehyde produced from a compound that is ingested, inhaled, or absorbed) to its corresponding acid in an NAD⁺-dependent reaction. For example, ALDHlAl oxidizes aldehydes derived from the breakdown of compounds, e.g., toxic compounds that are ingested, that are absorbed, that are inhaled, or that are produced during normal metabolism.

[0088] The term "ALDHlAl" encompasses ALDHlAl from various species. Amino acid sequences of ALDHlAl are publicly available. For example, a human ALDHlAl amino acid sequence is found under GenBank Accession Nos. NM_000689; a mouse ALDHlAl amino acid sequence is found under GenBank Accession No. NM_013467; and a rat ALDHlAl amino acid sequence is found under GenBank Accession No. NM_022407. The term "ALDHlAl" as used herein also encompasses fragments, fusion proteins, and variants (e.g., variants having one or more amino acid substitutions, addition, deletions, and/or insertions) that retain ALDHlAl enzymatic activity. Specific enzymatically active ALDHlAl variants, fragments, fusion proteins, and the like can be verified by adapting the methods described herein. An example of an ALDHlAl variant is an ALDHlAl with a 17 base pair (bp) deletion (-416/-432) or a 3 bp insertion (-524) in the

ALDHlAl promoter region, designated as ALDH1A1*2 and ALDH1A1*3, respectively

(Alcohol Clin Exp Res. 2003, 27: 1389-94.) An ALDHlAl variant retains at least about 1% of the enzymatic activity of a corresponding wild-type ALDHlAl enzyme.

[0089] In the specification, the singular forms also include the plural, unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this present disclosure belongs. In the case of conflict, the present specification will control.

[0090] All percentages and ratios used herein, unless otherwise indicated, are by weight.

2. Synthesis of Compounds

[0091] The general procedure for preparing compounds of the present disclosure is described as follows.

Briefly, animation of 2,4-dichloroquinazoline (A) by amino ester (B) to form Compound C. Compound C undergoes intermolecular cyclization by heat to afford Chloride Product D.

Chloride Product D then undergoes thiolation by thiourea (E) to yield Thiourea Compound F. The desired final product G is formed by nucleophilic substitution of Thiourea Compound F with a halide (R₃X).

2,2-dimethyl-5 hioxo-5,6-dihydroimidazo[1 ,2-c]quinazolin-3(2/-/)-one

3. Methods of Treatment and Prevention

[0092] The present disclosure provides various treatment and prevention methods, generally involving administering to a subject an effective amount of a compound of the present disclosure. Diseases and conditions associated with ALDH1A1 include cancer.

[0093] "Treating", includes any effect, e.g., lessening, reducing, modulating, or eliminating, that results in the improvement of the condition, disease, disorder, etc. "Treating" or "treatment" of a disease state includes: (1) inhibiting the disease state, i.e., arresting the development of the disease state or its clinical symptoms; (2) relieving the disease state, i.e., causing temporary or permanent regression of the disease state or its clinical symptoms; or (3) reducing or lessening the symptoms of the disease state.

[0094] "Preventing", refers to causing the clinical symptoms of the disease state not to develop in a subject that may be exposed to or predisposed to the disease state, but does not yet experience or display symptoms of the disease state.

Methods of Treating and Preventing Cancer

[0095] In one embodiment, the present disclosure provides a method of treating or preventing cancer comprising administering to a subject a pharmaceutical composition as described herein. In one embodiment, the present disclosure provides a method of treating or preventing cancer comprising administering to a subject a compound as described herein. In one embodiment, the present disclosure provides a method of treating or preventing cancer comprising administering to a subject a compound is selected from Table 1, or a pharmaceutically acceptable salt, solvate, or prodrug thereof.

[0096] In another embodiment, the method as described herein further comprises administering a cancer chemotherapeutic agent. In one embodiment, the chemotherapeutic agent is selected from non- peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor. In one embodiment, the proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony- stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[0097] In one embodiment, the compound and the chemotherapeutic agent are administered

simultaneously, staggered, alternating, or sequentially.

[0098] In one embodiment, the method as described herein further comprises administering ionizing radiation. In one embodiment, the ionizing radiation is administered via external beam radiation therapy or brachytherapy.

[0099] In one embodiment, the present disclosure provides a method of treating or preventing cancer in a subject comprising administering to the subject a first amount of a compound as described herein in a first treatment procedure, and a second amount of radiation in a second treatment procedure wherein, the first and second amounts together comprise a therapeutically effective amount. In one embodiment, the radiation is a radiopharmaceutical agent. In one embodiment, the radiation is an ionizing radiation administered via external beam radiation therapy or brachytherapy.

[00100] In one embodiment, the cancer is selected from solid tumors, skin cancers, myeloma, lymphoma, leukemia, ovarian cancer, lung cancer, brain cancer, pancreatic cancer, prostate cancer, colon cancer, colorectal cancer, breast cancer, liver cancer, kidney cancer, oral cancer, head cancer, neck cancer, throat cancer, and thyroid cancer.

[00101] In another embodiment, the method described herein provides a synergistic effect in the treatment of cancer.

[00102] In one embodiment, the present disclosure relates to a method of increasing the

sensitivity of a cancerous cells or cancer stem cells to a chemotherapeutic agent comprising administering to a subject a compound as described herein or a pharmaceutical composition as described herein. In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor. In one embodiment, the proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen apoptosis receptor agonists, interleukin-2 interferon-alpha (a), interferon-gamma (γ), colony- stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[00103] In one embodiment, the cancer is ovarian cancer.

[00104] The present disclosure provides methods of treating or preventing cancer in a subject.

The methods generally involve administering to a subject an effective amount of a compound of the present disclosure in conjunction with a standard cancer therapy. Standard cancer therapies include surgery (e.g., surgical removal of cancerous tissue), radiation therapy, bone marrow transplantation, chemotherapeutic treatment, biological response modifier treatment, and certain combinations of the foregoing.

[00105] Radiation therapy includes, but is not limited to, x-rays or gamma rays that are delivered from either an externally applied source such as a beam, or by implantation of small radioactive sources.

[00106] Chemotherapeutic agents are compounds that reduce proliferation of cancer cells, and encompass cytotoxic agents and cytostatic agents. Non-limiting examples of chemotherapeutic agents include alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, plant (vinca) alkaloids, and steroid hormones.

[00107] Agents that act to reduce cellular proliferation are known in the art and widely used. Such agents include alkylating agents, such as nitrogen mustards, nitrosoureas, ethylenimine derivatives, alkyl sulfonates, and triazenes, including, but not limited to, mechlorethamine, cyclophosphamide (Cytoxan.TM.), melphalan (L-sarcolysin), carmustine (BCNU), lomustine (CCNU), semustine (methyl-CCNU), streptozocin, chlorozotocin, uracil mustard, chlormethine, ifosfamide, chlorambucil, pipobroman, triethylenemelamine, trie thylenethiophosphor amine, busulfan, dacarbazine, and temozolomide.

[00108] Antimetabolite agents include folic acid analogs, pyrimidine analogs, purine analogs, and adenosine deaminase inhibitors, including, but not limited to, cytarabine (CYTOSAR-U), cytosine arabinoside, fluorouracil (5-FU), floxuridine (FudR), 6-thioguanine, 6-mercaptopurine (6-MP), pentostatin, 5 -fluorouracil (5-FU), methotrexate, 10-propargyl-5,8-dideazafolate (PDDF, CB3717), 5,8-dideazatetrahydrofolic acid (DDATHF), leucovorin, fludarabine phosphate, pentostatine, and gemcitabine.

[00109] Suitable natural products and their derivatives, (e.g., vinca alkaloids, antitumor

antibiotics, enzymes, lymphokines, and epipodophyllotoxins), include, but are not limited to, Ara- C, paclitaxel (Taxol®), docetaxel (Taxotere®), deoxycoformycin, mitomycin-C, L-asparaginase, azathioprine; brequinar; alkaloids, e.g. vincristine, vinblastine, vinorelbine, vindesine, etc.;

podophyllotoxins, e.g. etoposide, teniposide, etc.; antibiotics, e.g. anthracycline, daunorubicin hydrochloride (daunomycin, rubidomycin, cerubidine), idarubicin, doxorubicin, epirubicin and morpholino derivatives, etc.; phenoxizone biscyclopeptides, e.g. dactinomycin; basic

glycopeptides, e.g. bleomycin; anthraquinone glycosides, e.g. plicamycin (mithramycin);

anthracenediones, e.g. mitoxantrone; azirinopyrrolo indolediones, e.g. mitomycin; macrocyclic immunosuppressants, e.g. cyclosporine, FK-506 (tacrolimus, prograi), rapamycin, etc.; and the like.

[00110] Other anti-proliferative cytotoxic agents are navelbene, CPT-11, anastrazole, letrazole, capecitabine, reloxafine, cyclophosphamide, ifosamide, and droloxafine.

[00111] Microtubule affecting agents that have antiproliferative activity are also suitable for use and include, but are not limited to, allocolchicine (NSC 406042), Halichondrin B (NSC 609395), colchicine (NSC 757), colchicine derivatives (e.g., NSC 33410), dolstatin 10 (NSC 376128), maytansine (NSC 153858), rhizoxin (NSC 332598), paclitaxel (Taxol®), Taxol® derivatives, docetaxel (Taxotere®), thiocolchicine (NSC 361792), trityl cysterin, vinblastine sulfate, vincristine sulfate, natural and synthetic epothilones including but not limited to, eopthilone A, epothilone B, discodermolide; estramustine, nocodazole, and the like.

[00112] Hormone modulators and steroids (including synthetic analogs) that are suitable for use include, but are not limited to, adrenocorticosteroids, e.g. prednisone, dexamethasone, etc.;

estrogens and pregestins, e.g. hydroxyprogesterone caproate, medroxyprogesterone acetate, megestrol acetate, estradiol, clomiphene, tamoxifen; etc.; and adrenocortical suppressants, e.g. aminoglutethimide; 17a-ethinylestradiol; diethylstilbestrol, testosterone, fluoxymesterone, dromostanolone propionate, testolactone, methylprednisolone, methyl-testosterone, prednisolone, triamcinolone, chlorotrianisene, hydroxyprogesterone, aminoglutethimide, estramustine, medroxyprogesterone acetate, leuprolide, Flutamide (Drogenil), Toremifene (Fareston), and Zoladex®. Estrogens stimulate proliferation and differentiation; therefore, compounds that bind to the estrogen receptor are used to block this activity. Corticosteroids may inhibit T cell proliferation. [00113] Other chemotherapeutic agents include metal complexes, e.g. cisplatin (cis-DDP), carboplatin, etc.; ureas, e.g. hydroxyurea; and hydrazines, e.g. N-methylhydrazine;

epidophyllotoxin; a topoisomerase inhibitor; procarbazine; mitoxantrone; leucovorin; tegafur; etc. Other anti-proliferative agents of interest include immunosuppressants, e.g. mycophenolic acid, thalidomide, desoxyspergualin, azasporine, leflunomide, mizoribine, azaspirane (SKF 105685); Iressa® (ZD 1839, 4-(3-chloro-4-fluorophenylamino)-7-methoxy-6-(3-(4- morpholinyl)propoxy)qu- inazoline); etc.

[00114] "Taxanes" include paclitaxel, as well as any active taxane derivative or pro-drug.

"Paclitaxel" (which should be understood herein to include analogues, formulations, and derivatives such as, for example, docetaxel, TAXOL™, TAXOTERE™ (a formulation of docetaxel), 10-desacetyl analogs of paclitaxel and 3 'N-desbenzoyl-3 'N-t-butoxycarbonyl analogs of paclitaxel) may be readily prepared utilizing techniques known to those skilled in the art (see also WO 94/07882, WO 94/07881, WO 94/07880, WO 94/07876, WO 93/23555, WO 93/10076; U.S. Pat. Nos. 5,294,637; 5,283,253; 5,279,949; 5,274,137; 5,202,448; 5,200,534; 5,229,529; and EP 590,267), or obtained from a variety of commercial sources, including for example, Sigma Chemical Co., St. Louis, Mo. (T7402 from Taxus brevifolia; or T-1912 from Taxus yannanensis).

[00115] Biological response modifiers suitable for use in connection with the methods of the present disclosure include, but are not limited to, (1) inhibitors of tyrosine kinase (RTK) activity; (2) inhibitors of serine/threonine kinase activity; (3) tumor-associated antigen antagonists, such as antibodies that bind specifically to a tumor antigen; ( 4) apoptosis receptor agonists; (5) interleukin-2; (6) interferon- a.; (7) interferon -γ; (8) colony-stimulating factors; (9) inhibitors of angiogenesis; and (10) antagonists of tumor necrosis factor.

[00116] In one embodiment, the present disclosure provides a use of a pharmaceutical

composition as disclosed herein for the manufacture of a medicament for treating or preventing cancer.

[00117] In one embodiment, the present disclosure provides a use of a compound of formula (I) for the manufacture of a medicament for treating or preventing cancer.

[00118] In one embodiment, the present disclosure provides a use of a compound selected from

Table 1 herein, or a pharmaceutically acceptable salt, solvate, or prodrug thereof for the manufacture of a medicament for treating or preventing cancer.

[00119] In one embodiment, the medicament further comprises a cancer chemotherapeutic agent.

[00120] In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non- proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

[00121] In one embodiment, the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[00122] In one embodiment, the compound and the chemotherapeutic agent are administered simultaneously, staggered, alternating, or sequentially.

[00123] In one embodiment, the use further comprises administering ionizing radiation.

[00124] In one embodiment, the ionizing radiation is administered via external beam radiation therapy or brachytherapy.

[00125] In one embodiment, the present disclosure provides a use of a first amount of a

compound of formula (I) for the manufacture of a medicament for treating or preventing cancer in a first treatment procedure, wherein the use further comprises a second amount of radiation in a second treatment procedure wherein, the first and second amounts together comprise a therapeutically effective amount.

[00126] In one embodiment, the radiation is a radiopharmaceutical agent.

[00127] In one embodiment, the radiation is an ionizing radiation administered via external beam radiation therapy or brachytherapy.

[00128] In one embodiment, the cancer is selected from solid tumors, skin cancers, myeloma, lymphoma, leukemia, ovarian cancer, lung cancer, brain cancer, pancreatic cancer, prostate cancer, colon cancer, colorectal cancer, breast cancer, liver cancer, kidney cancer, oral cancer, head cancer, neck cancer, throat cancer, and thyroid cancer.

[00129] In one embodiment, the use provides a synergistic effect in the treatment of cancer.

[00130] In one embodiment, the present disclosure provides a use of a compound of formula (I) or a pharmaceutical composition as disclosed above for the manufacture of a medicament for increasing the sensitivity of cancerous cells or cancer stem cells to a chemotherapeutic agent.

[00131] In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non- proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

[00132] In one embodiment, the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen apoptosis receptor agonists, interleukin-2 interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

[00133] In one embodiment, the compound or pharmaceutical composition is administered by a route selected from topical, intramuscular, intravenous, subcutaneous, and oral.

[00134] In one embodiment, the compound or pharmaceutical composition is administered to the respiratory tract.

4. Pharmaceutical Compositions

[00135] In one embodiment, the present disclosure relates to a pharmaceutical composition

and a cancer chemotherapeutic agent:

(I),

or a pharmaceutically acceptable salt, solvate, or prodrug thereof, wherein

R¹ and R² are each independently selected from hydrogen and C₁-C6 alkyl,

R³ and R⁴ are each independently selected from hydrogen and C₁-C6 alkyl;

each R⁷ is independently selected from halogen, C₁-C6 alkyl, and OCH₃, and

n is 0, 1, 2, 3, 4, or 5;

provided that when one of R¹ and R² is hydrogen and the other is isopropyl,

[00136] In one embodiment, one of R¹ and R² is hydrogen and the other is Ci-C₆ alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain Ci-C₆ alkyl or branched C3-C6 alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain d- C₄ alkyl or branched C3-C4 alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain C₁-C₄ alkyl. In one embodiment, one of R¹ and R² is hydrogen and the other is branched C3-C4 alkyl.

[00137] In one embodiment, one of R³ and R⁴ is hydrogen and the other is Ci-C₆ alkyl. In one embodiment, one of R³ and R⁴ is hydrogen and the other is methyl or ethyl.

[00138] In one embodiment, one of R¹ and R² is hydrogen and the other is straight-chain C₁-C₄ alkyl; and one of R³ and R⁴ is hydrogen and the other is methyl or ethyl. In one embodiment, one of R¹ and R² is hydrogen and the other is branched C3-C4 alkyl; and one of R³ and R⁴ is hydrogen and the other is methyl or ethyl.

[00139] In one embodiment, n is 0, 1, 2, or 3. In one embodiment, n is 1, 2, or 3. In one

embodiment, n is 1. In one embodiment, n is 2.

[00140] In one embodiment, each R⁷ is Ci-C₆ alkyl. In one embodiment, each R⁷ is independently methyl, ethyl, or isopropyl. In one embodiment, each R⁷ is halogen. In one embodiment, each R⁷ is independently chloro or fluoro. In one embodiment, R⁷ is chloro. In one embodiment, R⁷ is fluoro. In one embodiment, one or more R⁷ is Ci-C₆ alkyl and one or more R⁷ is halogen. In one embodiment, one or more R⁷ is independently methyl, ethyl, or isopropyl and one or more R⁷ is independently chloro or fluoro. In one embodiment, one or more R⁷ is Ci-C₆ alkyl and one or more R⁷ is OCH₃. In one example, one or more R⁷ is independently methyl, ethyl, or isopropyl and one or more R⁷ is OCH₃. In one embodiment, one or more R⁷ is halogen and one or more R⁷ is OCH₃. In one example, one or more R⁷ is independently chloro or fluoro and one or more R⁷ is OCH₃.

[00141] It will be apparent to one skilled in the art based one the present disclosure that any of the embodiments described above for each of R¹, R², R³, R⁴, R⁷, and n can be combined in any manner.

[00142] In one embodiment, a compound of the present disclosure is of one of the following formulae:

[00143] In one embodiment, the present disclosure relates to a pharmaceutical composition

comprising a compound selected from Table 1, or a pharmaceutically acceptable salt, solvate, or prodrug thereof, and a cancer chemotherapeutic agent.

[00144] In one embodiment, the chemotherapeutic agent is selected from non-peptidic (non- proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone- deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

[00145] In another embodiment, the proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor. [00146] In one embodiment, the compound or pharmaceutical composition is administered by a route selected from topical, intramuscular, intravenous, subcutaneous, and oral. In one embodiment, the compound or pharmaceutical composition is administered to the respiratory tract.

[00147] The present disclosure provides pharmaceutical compositions comprising a compound of the present disclosure (where a compound of the present disclosure is also referred to herein as "active agent" of the present disclosure, or "subject active agent"). The compound of the present disclosure can be formulated with one or more pharmaceutically acceptable excipients. A wide variety of pharmaceutically acceptable excipients are known in the art and need not be discussed in detail herein. Pharmaceutically acceptable excipients have been amply described in a variety of publications, including, for example, A. Gennaro (2000) "Remington: The Science and Practice of Pharmacy," 20th edition, Lippincott, Williams, & Wilkins; Pharmaceutical Dosage Forms and Drug Delivery Systems (1999) H. C. Ansel et al., eds., 7th ed., Lippincott, Williams, & Wilkins; and Handbook of Pharmaceutical Excipients (2000) A. H. Kibbe et al., eds., 3rd ed. Amer.

Pharmaceutical Assoc.

[00148] The pharmaceutically acceptable excipients, such as vehicles, adjuvants, carriers or diluents, are readily available to the public. Moreover, pharmaceutically acceptable auxiliary substances, such as pH adjusting and buffering agents, tonicity adjusting agents, stabilizers, wetting agents and the like, are readily available to the public.

[00149] In the subject methods, a subject ALDH1A1 activity inhibitor may be administered to the host using any convenient means capable of treating cancer. Thus, a subject ALDH1A1 activity inhibitor can be incorporated into a variety of formulations for therapeutic administration. More particularly, a subject ALDH1A1 activity inhibitor can be formulated into pharmaceutical compositions by combination with appropriate, pharmaceutically acceptable carriers or diluents, and may be formulated into preparations in solid, semi-solid, liquid or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants and aerosols.

[00150] In pharmaceutical dosage forms, a subject active agent may be administered in the form of their pharmaceutically acceptable salts, or a subject active agent may be used alone or in appropriate association, as well as in combination, with other pharmaceutically active compounds. The following methods and excipients are merely exemplary and are in no way limiting.

[00151] For oral preparations, a subject active agent can be used alone or in combination with appropriate additives to make tablets, powders, granules or capsules, for example, with conventional additives, such as lactose, mannitol, corn starch or potato starch; with binders, such as crystalline cellulose, cellulose derivatives, acacia, corn starch or gelatins; with disintegrators, such as corn starch, potato starch or sodium carboxymethylcellulose; with lubricants, such as talc or magnesium stearate; and if desired, with diluents, buffering agents, moistening agents, preservatives and flavoring agents.

[00152] A subject active agent can be formulated into preparations for injection by dissolving, suspending or emulsifying them in an aqueous or nonaqueous solvent, such as vegetable or other similar oils, synthetic aliphatic acid glycerides, esters of higher aliphatic acids or propylene glycol; and if desired, with conventional additives such as solubilizers, isotonic agents, suspending agents, emulsifying agents, stabilizers and preservatives.

[00153] A subject active agent can be utilized in aerosol formulation to be administered via

inhalation. A subject active agent can be formulated into pressurized acceptable propellants such as dichlorodifluoromethane, propane, nitrogen and the like.

[00154] Furthermore, a subject active agent can be made into suppositories by mixing with a variety of bases such as emulsifying bases or water-soluble bases. An active agent can be administered rectally via a suppository. The suppository can include vehicles such as cocoa butter, carbowaxes and polyethylene glycol monomethyl ethers, which melt at body temperature, yet are solidified at room temperature.

[00155] Unit dosage forms for oral or rectal administration such as syrups, elixirs, and

suspensions may be provided wherein each dosage unit, for example, teaspoonful, tablespoonful, tablet or suppository, contains a predetermined amount of the subject active agent. Similarly, unit dosage forms for injection or intravenous administration may comprise a subject active agent in a composition as a solution in sterile water, normal saline or another pharmaceutically acceptable carrier.

[00156] The term "unit dosage form," as used herein, refers to physically discrete units suitable as unitary dosages for human and animal subjects, each unit containing a predetermined quantity of a subject active agent calculated in an amount sufficient to produce the desired effect in association with a pharmaceutically acceptable diluent, carrier or vehicle. The specifications for a subject active agent depend on the particular compound employed and the effect to be achieved, and the pharmacodynamics associated with each compound in the host.

[00157] A subject active agent can be formulated for administration by injection. Typically, injectable compositions are prepared as liquid solutions or suspensions; solid forms suitable for solution in, or suspension in, liquid vehicles prior to injection may also be prepared. The preparation may also be emulsified or the active ingredient encapsulated in liposome vehicles. [00158] In some embodiments, a subject active agent is delivered by a continuous delivery system. The term "continuous delivery system" is used interchangeably herein with "controlled delivery system" and encompasses continuous (e.g., controlled) delivery devices (e.g., pumps) in combination with catheters, injection devices, and the like, a wide variety of which are known in the art.

[00159] Suitable excipient vehicles are, for example, water, saline, dextrose, glycerol, ethanol, or the like, and combinations thereof. In addition, if desired, the vehicle may contain minor amounts of auxiliary substances such as wetting or emulsifying agents or pH buffering agents. Actual methods of preparing such dosage forms are known, or will be apparent, to those skilled in the art. See, e.g., Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa., 17th edition, 1985. The composition or formulation to be administered will, in any event, contain a quantity of the agent adequate to achieve the desired state in the subject being treated.

[00160] Depending on the subject and condition being treated and on the administration route, the subject compounds may be administered in dosages of, for example, 0.1 μg to 10 mg/kg body weight per day. The range is broad, since in general the efficacy of a therapeutic effect for different mammals varies widely with doses typically being 20, 30 or even 40 times smaller (per unit body weight) in man than in the rat. Similarly the mode of administration can have a large effect on dosage. Thus, for example, oral dosages may be about ten times the injection dose. Higher doses may be used for localized routes of delivery.

[00161] For example, a subject ALDH1A1 activity modulator can be administered in an amount of from about 1 mg to about 1000 mg per dose, e.g., from about 1 mg to about 5 mg, from about 5 mg to about 10 mg, from about 10 mg to about 20 mg, from about 20 mg to about 25 mg, from about 25 mg to about 50 mg, from about 50 mg to about 75 mg, from about 75 mg to about 100 mg, from about 100 mg to about 125 mg, from about 125 mg to about 150 mg, from about 150 mg to about 175 mg, from about 175 mg to about 200 mg, from about 200 mg to about 225 mg, from about 225 mg to about 250 mg, from about 250 mg to about 300 mg, from about 300 mg to about 350 mg, from about 350 mg to about 400 mg, from about 400 mg to about 450 mg, from about 450 mg to about 500 mg, from about 500 mg to about 750 mg, or from about 750 mg to about 1000 mg per dose.

[00162] An exemplary dosage may be a solution suitable for intravenous administration; a tablet taken from two to six times daily, or one time -release capsule or tablet taken once a day and containing a proportionally higher content of active ingredient, etc. The time -release effect may be obtained by capsule materials that dissolve at different pH values, by capsules that release slowly by osmotic pressure, or by any other known means of controlled release. [00163] Those of skill in the art will readily appreciate that dose levels can vary as a function of the specific compound, the severity of the symptoms and the susceptibility of the subject to side effects. Preferred dosages for a given compound are readily determinable by those of skill in the art by a variety of means.

[00164] Unit dosage forms for oral or rectal administration such as syrups, elixirs, and

suspensions may be provided wherein each dosage unit, for example, teaspoonful, tablespoonful, tablet or suppository, contains a predetermined amount of the composition containing one or more compounds of the present disclosure. Similarly, unit dosage forms for injection or intravenous administration may comprise the compound (s) in a composition as a solution in sterile water, normal saline or another pharmaceutically acceptable carrier.

[00165] In some embodiments, multiple doses of a subject compound are administered. The

frequency of administration of a subject compound can vary depending on any of a variety of factors, e.g., severity of the symptoms, etc. For example, in some embodiments, a subject compound is administered once per month, twice per month, three times per month, every other week (qow), once per week (qw), twice per week (biw), three times per week (tiw), four times per week, five times per week, six times per week, every other day (qod), daily (qd), twice a day (qid), or three times a day (tid). As discussed above, in some embodiments, a subject compound is administered continuously.

[00166] The duration of administration of a subject compound, e.g., the period of time over which a subject compound is administered, can vary, depending on any of a variety of factors, e.g., patient response, etc. For example, a subject compound can be administered over a period of time ranging from about one day to about one week, from about two weeks to about four weeks, from about one month to about two months, from about two months to about four months, from about four months to about six months, from about six months to about eight months, from about eight months to about 1 year, from about 1 year to about 2 years, or from about 2 years to about 4 years, or more. In some embodiments, a subject compound is administered for the lifetime of the individual.

[00167] A subject ALDH1A1 activity inhibitor is administered to an individual using any

available method and route suitable for drug delivery, including in vivo and ex vivo methods, as well as systemic and localized routes of administration. Administration can be acute (e.g., of short duration, e.g., a single administration, administration for one day to one week), or chronic (e.g., of long duration, e.g., administration for longer than one week, e.g., administration over a period of time from about 2 weeks to about one month, from about one month to about 3 months, from about 3 months to about 6 months, from about 6 months to about 1 year, or longer than one year). [00168] Conventional and pharmaceutically acceptable routes of administration include intranasal, intramuscular, intratracheal, subcutaneous, intradermal, transdermal, sublingual, topical application, intravenous, rectal, nasal, oral, and other enteral and parenteral routes of administration. Routes of administration may be combined, if desired, or adjusted depending upon the agent and/or the desired effect. The compound can be administered in a single dose or in multiple doses.

[00169] An active agent can be administered to a host using any available conventional methods and routes suitable for delivery of conventional drugs, including systemic or localized routes. In general, routes of administration contemplated by the present disclosure include, but are not necessarily limited to, enteral, parenteral, or inhalational routes.

[00170] Parenteral routes of administration other than inhalation administration include, but are not necessarily limited to, topical, transdermal, subcutaneous, intramuscular, intraorbital, intracapsular, intraspinal, intrasternal, and intravenous routes, i.e., any route of administration other than through the alimentary canal. Parenteral administration can be carried to effect systemic or local delivery of the agent. Where systemic delivery is desired, administration typically involves invasive or systemically absorbed topical or mucosal administration of pharmaceutical preparations.

[00171] The agent can also be delivered to the subject by enteral administration. Enteral routes of administration include, but are not necessarily limited to, oral and rectal (e.g., using a suppository) delivery.

[00172] Methods of administration of the agent through the skin or mucosa include, but are not necessarily limited to, topical application of a suitable pharmaceutical preparation, transdermal transmission, injection and epidermal administration. For transdermal transmission, absorption promoters or iontophoresis are suitable methods. Iontophoretic transmission may be

accomplished using commercially available "patches" which deliver their product continuously via electric pulses through unbroken skin for periods of several days or more.

5. Examples

Example 1: Inhibitory activity of compounds against ALDH1A1

[00173] Method: To prepare human ALDH1A1 recombinant enzyme, full-length human

ALDH1 Al cDNA was synthesized based on published DNA sequence (GenBank ID:

NM_000689). The synthetic gene was cloned into the Nhel/EcoRI sites of the His-tag vector, pTrcHis, for protein expression. All the vectors were transformed into BL21 E. coli host cells and subjected to 0.5 mM isopropyl β-D-l-thiogalactopyranoside (IPTG) induction for protein expression at 30°C. Purifications of the recombinant proteins by affinity nickel columns (HisTrap, GE Healthy Science, USA) were carried out using standard protocols according to manufacturer's instructions (Novagen, USA).

[00174] An example of the enzymatic assay is described as follows. The reaction cocktails were added into the wells in a 96-well plate and then put on a shaker for mixing. After 5 minutes of mixing, 2 μΕ of recombinant ALDH1 Al enzyme was added to each well with DMSO as blank control in the plate. The plate was again put on shaker for another 5 minutes of shaking to enhance bonding between testing compounds and the enzyme. 2μΕ of 1M acetyladehyde in water was then added to each of wells containing the above reaction mixture. After a short vigorous mixing, the UV plate was fed into a plate reader to measure kinetic optical density (O.D.) at wavelength 340 nm at 25°C over 4 minutes. Each point of measurement was taken at a time interval of 40 seconds.

[00175] Results: The half maximal inhibitory concentration (IC₅₀) values for compounds of the present disclosure against ALDH1A1 are listed in Table 2.

Table 2: Half Maximal Inhibitory Concentration (IC₅₀) of Compounds Against ALDH1A1

Compound no. ic₅₀

ALDH1A1 Inhibition (μΜ)

82 0.69

85 0.48

86 0.44

88 0.41

91 0.37

93 0.39

95 0.49

106 0.57

107 1.18

114 0.59

Example 2: Selectivity of Compound 5 with Other ALDH Isozymes

[00176] The specificity of Compound 5 against ALDH1A1, and other ALDH isozymes including

ALDH2, ALDH3A1, ALDH4A1, ALDH7A1, and ADH1B1 was determined.

[00177] Method: Isozyme-specific inhibition of Compound 5 was evaluated using standard

spectrometric ALDH enzymatic assays as described previously (e.g. Chen et. al, (2008) Science 321: 1493-1495, Sheikh et al. (1997) J. Biol. Chem. 272:18817-18822). Compound 5 (20 μΜ) was tested against purified human recombinant ALDH isozymes. In each assay, 10-50 μg of each isozyme were used with 10 mM of acetaldehyde as the substrate and 2.5 mM of NAD+ as the cofactor. Enzymatic activities were standardized using DMSO alone as the control (expressed as 100% activity).

[00178] Results: As shown in Figure 1, Compound 5 is a highly selective ALDH1A1 inhibitor

(99% inhibition at 20 μΜ) while no inhibitory activity against other five ALDH isozymes was observed.

Example 3: In vitro anti-cancer activity of the compounds in combination with paclitaxel and doxorubicin

[00179] Method: Cell cultures (5000 cells/well) in medium containing 5% fetal bovine serum

(FBS) were incubated in a 96-well plate for 24 h at 37 °C supplemented with 5% C0₂. Basal cells were fixed with 25 μί of 50% (w/v) trichloroacetic acid (TCA) (final 10%) for 30-min as Tz. Compound 5 at various concentrations was added to the cell cultures and then the suction of the basal cells with TCA was performed. The basal wells were washed with phosphate buffer saline (PBS, 100 μί), and incubated for 48-h or 72-h treatment before reaction was terminated, followed by 30-min incubation at RT. After suction of the cells with TCA, all wells (including basal wells) were washed with PBS (100 μί) and air-dried for 20 min in the hood.

Sulforhodamine B (SRB) solution (50 μί) at 0.4% (w/v) in 1% acetic acid was added to each well, followed by 10-min incubation at RT. Unbound dye was removed by washing twice with 1% acetic acid (100 μΐ_^), and the plates were air dried for 30 min or overnight. Cells were solubilized with 10 mM trizma base (100 μΐ_^). The plate was read at 515 nm detection in ELISA reader. Percentage growth inhibition was appropriately calculated.

[00180] Results: Compound 5 demonstrated significant synergistic effects (or sensitization) with paclitaxel (Figure 2) or doxorubicin (Figure 3) in two MDR ovarian cell lines, NCI/ ADR RES and TOV-21G-RT cells. In addition, analysis of the Combination Index (CI) was also performed, which showed strong synergistic effects of Compound 5 with pacitaxel and doxorubicin in those cancer cell lines (see Table 3).

[00181] Figure 2: (A) NCI/ADR-RES cells were treated with the indicated concentration of

paclitaxel in the absence or presence of Compound 5(3 μΜ) for 48 h; (B) TOV-21G-RT cells were treated with the indicated concentration of paclitaxel in the absence or presence of

Compound 5 (10 μΜ) for 48 h. Then, the cell growth was examined using SRB assay, and mean IC₅₀ values were subsequently determined. Mean ± SE of five independent experiments (each in triplicate).

[00182] Figure 3: (A) NCI/ADR-RES cells were treated with the indicated concentration of

doxorubicin in the absence or presence of Compound 5 (3 μΜ) for 48 h; (B) TOV-21G-RT cells were treated with the indicated concentration of doxorubicin in the absence or presence of Compound 5 (10 μΜ) for 48 h. The cell growth was detected by SRB assay, and mean IC₅₀ values were subsequently determined. Mean ± SE of five independent experiments (each in triplicate).

Table 3: Calculation of Combination Index for Compound 5 with Chemotherapies

Note: The mean combination index value, resulting from separate experiments at multiple effect levels, CI <1 indicates synergism, CI = 1 indicates additive effect, and CI >1 indicates antagonism.

INCORPORATION BY REFERENCE

[00183] The entire disclosure of each of the patent documents and scientific articles referred to herein is incorporated by reference for all purposes. OTHER EMBODIMENTS

While the present disclosure has been described in conjunction with the detailed description thereof, the foregoing description is intended to illustrate and not limit the scope of the present disclosure, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the present disclosure encompassed by the appended claims.

Claims

CLAIMS What is claimed is:

1. A pharmaceutical composition comprising a compound of formula (I) and a

chemo

or a pharmaceutically acceptable salt, solvate, or prodrug thereof, wherein

is selected from , , and

R¹ and R² are each independently selected from hydrogen and C1-C6 alkyl;

R³ and R⁴ are each independently selected from hydrogen and C1-C6 alkyl;

each R⁷ is independently selected from halogen, C1-C6 alkyl, and OCH₃; and

n is 0, 1, 2, 3, 4, or 5;

provided that when one of R¹ and R² is hydrogen and the other is isopropyl,

2. The composition of claim 1, wherein one of R¹ and R² is hydrogen and the other is C1-C6 alkyl.

3. The composition of any one of claims 1-2, wherein one of R³ and R⁴ is hydrogen and the other is C1-C6 alkyl.

4. The composition of claim 3, wherein one of R³ and R⁴ is hydrogen and the other is methyl or ethyl.

5. The composition of any one of claims 1-4, wherein n is 0, 1, 2, or 3.

6. The composition of claim 5, wherein n is 1, 2, or 3.

7. The composition of claim 6, wherein n is 1.

8. The composition of claim 6, wherein n is 2.

9. The composition of any one of claims 6-8, wherein each R⁷ is Ci-C₆ alkyl.

10. The composition of claim 9, wherein each R⁷ is methyl, ethyl, or isopropyl.

11. The composition of any one of claims 6-8, wherein each R⁷ is halogen.

12. The composition of claim 11, wherein R⁷ is fluoro.

13. A pharmaceutical composition comprising a compound selected from Table 1, or a pharmaceutically acceptable salt, solvate, or prodrug thereof, and a cancer chemotherapeutic agent.

14. The pharmaceutical composition of any one of claims 1-13, wherein the

chemotherapeutic agent is selected from non-peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony- stimulating factors, histone-deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

15. The pharmaceutical composition of claim 14, wherein the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

16. Use of a pharmaceutical composition of any one of claims 1 -15 for the manufacture of a medicament for treating or preventing cancer.

17. Use of a compound of formula (I) of claim 1 for the manufacture of a medicament for treating or preventing cancer.

18. Use of a compound selected from Table 1 , or a pharmaceutically acceptable salt, solvate, or prodrug thereof for the manufacture of a medicament for treating or preventing cancer.

19. The use of any one of claims 17-18, wherein the medicament further comprises a cancer chemotherapeutic agent.

20. The use of claim 19, wherein the chemotherapeutic agent is selected from non-peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone-deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

21. The use of claim 20, wherein the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen, apoptosis receptor agonists, interleukin-2, interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

22. The use of any one of claims 17-21 , wherein the compound and the chemotherapeutic agent are administered simultaneously, staggered, alternating, or sequentially.

23. The use of any one of claims 17-18 further comprising administering ionizing radiation.

24. The use of claim 23, wherein the ionizing radiation is administered via external beam radiation therapy or brachytherapy.

25. Use of a first amount of a compound of formula (I) of claim 1 for the manufacture of a medicament for treating or preventing cancer in a first treatment procedure, wherein the use further comprises a second amount of radiation in a second treatment procedure wherein, the first and second amounts together comprise a therapeutically effective amount.

26. The use of claim 25, wherein the radiation is a radiopharmaceutical agent.

27. The use of claim 25, wherein the radiation is an ionizing radiation administered via external beam radiation therapy or brachytherapy.

28. The use of any one of claims 16-27, wherein the cancer is selected from solid tumors, skin cancers, myeloma, lymphoma, leukemia, ovarian cancer, lung cancer, brain cancer, pancreatic cancer, prostate cancer, colon cancer, colorectal cancer, breast cancer, liver cancer, kidney cancer, oral cancer, head cancer, neck cancer, throat cancer, and thyroid cancer.

29. The use of any one of claims 16 or 19-28, wherein the use provides a synergistic effect in the treatment of cancer.

30. Use of a compound of formula (I) of claim 1 or a pharmaceutical composition of any one of claims 1-15 for the manufacture of a medicament for increasing the sensitivity of cancerous cells or cancer stem cells to a chemotherapeutic agent.

31. The use of claim 30, wherein the chemotherapeutic agent is selected from non-peptidic (non-proteinaceous) compounds that reduce proliferation of cancer cells, cytotoxic agents, cytostatic agents, alkylating agents, nitrosoureas, antimetabolites, antitumor antibiotics, taxanes, microtubule affecting agents, metal complexes, steroid hormones, tyrosine kinase and/or serine/threonine inhibitors, inhibitors of angiogenesis, colony-stimulating factors, histone-deacetylase inhibitors (HDAC inhibitors), and antagonists of tumor necrosis factor.

32. The use of claim 31 , wherein the non-proteinaceous compounds that reduce proliferation of cancer cells is selected from tumor-associated antigen antagonists, antibodies that bind specifically to a tumor antigen apoptosis receptor agonists, interleukin-2 interferon-alpha (a), interferon-gamma (γ), colony-stimulating factors, inhibitors of angiogenesis, and antagonists of tumor necrosis factor.

33. The use of any one of claims 16-32, wherein the compound or pharmaceutical composition is administered by a route selected from topical, intramuscular, intravenous, subcutaneous, and oral.

34. The use of claim 33, wherein the compound or pharmaceutical composition is administered to the respiratory tract.