NZ719050B2 - Combination therapy combining a CDK4/6 inhibitor and a PI3K inhibitor for use in the treatment of cancer - Google Patents

Abstract

Provided is a combination of a cyclin dependent kinase 4 or cyclin dependent kinase 6 (CDK4/6) inhibitor and a phosphatidylinositol 3-kinase (PI3K) inhibitor useful for the treatment of cancer. A preferred CDK4/6 inhibitor is a compound of Formula A (7-Cyclopentyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid dimethylamide) (ribociclib). Preferred PI3K inhibitors are the compounds of Formula B1 (5-(2,6-di-4-morpholinyl-4-pyrimidinyl)-4-(trifluoromethyl)-2-pyrimidinamine) (buparlisib) and Formula B2 ((S)-Pyrrolidine-1,2-dicarboxylic acid 2-amide 1-({4-methyl-5-[2-(2,2,2-trifluoro-1,1-dimethyl-ethyl)-pyridin-4-yl]-thiazol-2-yl}-amide)) (alpelisib). no)-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid dimethylamide) (ribociclib). Preferred PI3K inhibitors are the compounds of Formula B1 (5-(2,6-di-4-morpholinyl-4-pyrimidinyl)-4-(trifluoromethyl)-2-pyrimidinamine) (buparlisib) and Formula B2 ((S)-Pyrrolidine-1,2-dicarboxylic acid 2-amide 1-({4-methyl-5-[2-(2,2,2-trifluoro-1,1-dimethyl-ethyl)-pyridin-4-yl]-thiazol-2-yl}-amide)) (alpelisib).

Description

PATENTS FORM NO. 5 Our ref: DK0237274NZPR Divisional application out of NZ 618745 NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATlON Combination therapy ing a CDK4/6 inhibitor and a Pl3K inhibitor for use in the treatment of cancer We, Novartis AG, of Lichtstrasse 35, CH-4056 Basel, Switzerland, hereby declare the invention, for which we pray that a patent may be d to us and the method by which it is to be performed, to be particularly described in and by the following statement: (followed by page 1a) COMBINATION THERAPY COMPRISING A CDK4/6 TOR AND A PI3K INHIBITOR FOR USE IN THE TREATMENT OF CANCER FIELD OF THE DISCLOSURE A combination of a cyclin ent kinase 4/6 (CDK4/6) inhibitor and a atidylinositol 3—Kinase nase) inhibitor for the treatment of solid tumors and hematological malignancies. This disclosure also relates to the use of the combination thereof, in the management of hyperproliferative diseases like cancer.

RELATED BACKGROUND ART Cyclin ent kinase 4/6 (CDK4/6) inhibitors are described in, for example, W02007/140222 and WOZOIO/020675 which are hereby incorporated by reference in entirety.

Phosphatidylinositol 3~Kinase (PI3Kinase) inhibitors are described in, for example, W02004/048365, W02007/084786, W02004/O96797, W02010/029082, W02006/122806 which is hereby incmporated by reference in entirety.

BRIEF SUMMARY OF THE DISCLOSURE The disclosure provides a combination comprising a first agent that inhibits the CDK4/6 pathway and a second agent that inhibits PI3Kinase. In another , the disclosure provides combinations including pharmaceutical compositions comprising a therapeutically effective amount of a first agent that inhibits CDK4/6, a second agent that inhibits PI3Kinase, and a pharmaceutically acceptable carrier.

Furthermore, the present disclosure provides for the use of a therapeutically effective amount of a ation comprising a first agent that inhibits the CDK4/6 pathway and a second agent that inhibits PI3Kinase, or a pharmaceutically acceptable salt or pharmaceutical ition thereof, in the manufacture of a medicament for ng cancer.

The present disclosure has a therapeutic use in the treatment of various erative diseases.

The above combinations and itions can be administered to a system comprising cells or tissues, as well as a human patient or and animal subject. [followed by page 2] The first agent that inhibits the CDK4/6 y is Compound A which is 7- Cyclopentyl-Z-(S-piperaziny1-pyridinylamino)-7H-pyrrolo[2,3-d]pyrimidine carboxylic acid dimethylamide or pharmaceutically acceptable salt(s) thereof.

Compound A is described by Formula A: D34“ HN N/ N 0 VI C H Formula A or pharmaceutically acceptable salt(s) thereof.

The second agent that inhibits PI3Kinase is Compound B1 described by Formula B 1: Formula B1 or pharmaceutically acceptable salt(s) thereof.

Compound B1 has been described with several names, such as fluoromethyl) (2,6—dimorpholinopyrimidin—4-yl)pyridin—Z—amine; 5—(2,6-di—morpholin~4—yl-pyrimidin— 4-trifluoromethyl—pyridin2—ylamine; 5-(2,6~Di—4—m01pholinyl-4—pyrimidinyl)—4— trifluoromethylpyridin-Z-amine; or CAS name 5—(2,6-di~4—mOIpholinylpyrimidinyl) — 4- (trifluoromethyl)pyrimidinamine.

Alternatively, the second agent that inhibits PI3Kinase is Compound B2 described by Formula B2: \ YH/ri a B2 or pharmaceutically acceptable salt(s) thereof.

Compound B2 is known as (S)—Pyrrolidine—1,2-dicarboxylic acid 2—amide l-( {4— methyl-S— [2—(2,2,2—triflu0ro- 1 , 1—dimethyl—ethyl)—pyridin—4—yl]—thiazol~2-yl} ).

The present ion therefore provides a combination comprising a first agent that is a cyclin dependent kinase 4 or cyclin dependent kinase 6 (CDK4/6) inhibitor, wherein the first agent is Compound A described by Fonnula A: N \ \ HN/kN/.134N O | C H Formula A, or a pharmaceutically acceptable salt thereof, and a second agent that is a PI3Kinase inhibitor, n the second agent is (i) Compound B1 described by Fon’nula B1: Formula B l, or a pharmaceutically acceptable salt thereof, (ii) Compound B2 described by Formula B2: \ THY“ O/\NH2 Formula B2, or a pharmaceutically acceptable salt thereof.

The present invention also provides these ations for use in the treatment of , and these combinations for use in the treatment of various s as described The present invention also provides the use of these combinations in the manufacture of a medicament for treating cancer and the use of these combinations in the manufacture of a medicament for treating various s as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates the results when the ation of Compound A and Compound B1 or Compound B2, is used to treat MDA—MB—453 cells. The resulting inhibition values were used by CHALICE software to generate Inhibition and ADD Excess Inhibition matrices, as well as the isobolograms.

Figure 2 illustrates the results when the combination of Compound A and Compound B1 or Compound B2, is used to treat HCT—l 16 cells. The resulting inhibition values were used by CHALICE software to te Inhibition and ADD Excess Inhibition matrices, as well as the isobolograms.

Figure 3 illustrates the s when the combination of Compound A and Compound B1 or Compound B2, is used to treat MCF-7 cells. The resulting inhibition values were used by CHALICE software to generate Inhibition and ADD Excess Inhibition matrices, as well as the isobolograms.

Figure 4 illustrates the results when the combination of Compound A and Compound B2, is used to treat T47—D cells. The resulting inhibition values were used by E software to generate Inhibition and ADD Excess Inhibition matrices, as well as the isobolograms.

DETAILED DESCRIPTION OF THE DISCLOSURE The disclosure provides a combination comprising a first agent that inhibits the CDK4/6 y and a second agent that ts PI3Kinase. In another aspect, the disclosure provides combinations including pharmaceutical compositions sing a eutically effective amount of a first agent that inhibits CDK4/6, a second agent that inhibits PI3Kinase, and a pharmaceutically acceptable carrier.

Furthermore, the present disclosure provides for the use of a therapeutically effective amount of a ation comprising a first agent that ts the CDK4/6 pathway and a second agent that inhibits PI3 Kinase, or a pharmaceutically acceptable salt or pharmaceutical composition thereof, in the manufacture of a medicament for treating cancer.

The present disclosure has a therapeutic use in the treatment of various proliferative diseases.

The above combinations and compositions can be administered to a system comprising cells or tissues, as well as a human patient or and animal subject.

The first agent that inhibits the CDK4/6 pathway is Compound A which is 7- Cyclopentyl—2-(5—piperazin- l ridinylamino)—7H—pyrrolo [2,3 -d]pyrimidine carboxylic acid dimethylamide or pharmaceutically able salt(s) thereof.

Compound A is described by Formula A: Formula A.

The second agent that inhibits PBKinase is Compound Bl described by a B 1: Formula B1 or pharmaceutically acceptable salt(s) thereof.

Compound B1 has been bed with several names, such as 4—(trifluoromethyl)—5- (2,6-dimorpholinopyrimidin—4—yl)pyridin-2—amine; 5—(2,6-di—morpholin—4—yl-pyrimidin— 4—yl)-4—trifluoromethyl—pyridin2~ylamine; 5-(2,6-Di—4-morpholinylpyrimidinyl)—4- trifluoromethylpyridin-Z-amine; or CAS name 5-(2,6-di—4-morpholinyl—4—pyrimidinyl) — 4— (trifluoromethyl)pyrimidinamine.

Alternatively, the second agent that inhibits P13Kinase is Compound B2 descn'bed by Formula B2: [followed by page 6a] Formula B2 or pharmaceutically acceptable salt(s) thereof.

Compound BZ is known as (S)—Pyrrolidine-1,2-dicarboxylic acid 2—amide l—( {4— methyl-S-[2—(2,2,2-trifluoro- l , l -dimethyl-ethyl)-pyridin—4—yl]—thiazol—2~yl} —amide).

The present disclosure includes a method of treating a hyperproliferative disease, preferably cancer. The compounds of the present disclosure tors of CDK4/6 and P13K, and therefore may be capable of treating diseases n the ying pathology is (at least in part) mediated by activated CDK4/6 and/or PI3K pathway. Such diseases include cancer and other diseases in which there is a disorder of cell proliferation, apoptosis, or differentiation.

Thus the combination of the present disclosure may be useful in the treatment of RB+W (retinoblastoma protein positive) tumours, including tumours harbouring activating mutations in Ras, Raf, Growth Factor Receptors, P13K,or over-expression of Growth Factor Receptors, or inactivation of p16. The compounds of the present disclosure may also be useful in the treatment of tumours with cations of CDK4 and CDK6 genes as well as, tumours over-expressing cyclin partners of the cyclin ent kinases. The compounds of the present disclosure may also be useful in the treatment of RB—ve tumours.

The combination of the present disclosure may also be useful in the treatment tumours with c aberrations that activate the CDK4/6 kinase ty. These include, but are not d to, s with D-cyclin translocations such as mantle cell lymphoma [followed by page 6b] and le myeloma, D-cyclin amplifications such as breast cancer and squamous cell esophageal cancer, CDK4 amplifications such as liposarcoma, CDK6 amplifications or overexpressions such as T—cell lymphoma and p16 inactivation such as melanoma, non— small cell lung cancer and pancreatic cancer.

The combination of the present disclosure may be useful in the treatment of cancers that have genetic aberrations in the upstream regulators of D-cyclins, where the defect s in an increase of ins abundance, can also be considered for treatment.

These include, but are not limited to, acute myeloid leukemia with FLT3 activation, breast cancers with Her2/neu overexpression, ER dependency or triple negative phenotype, colon cancers with activating ons of the MAPK, PI3K or WNT pathway, melanomas with activating mutations of MAPK y, non small cell lung s with activating aberrations of EGFR pathway and pancreatic cancers with activating aberrations of MAPK pathway including K—Ras mutations. [followed by page 7] The ation of the t disclosure may be useful in the treatment of cancers that have activating mutations of PI3K. These include, but not limited to, breast cancer, endometrium cancer, urinary track , melanoma, colon , stomach cancer, cervical cancer, te cancer and ovarian cancer. es of cancers which may be treated With a compound of the present disclosure include but are not limited to, carcinoma, for example a carcinoma of the bladder, breast, colon (e.g. colorectal carcinomas such as colon adenocarcinoma and colon adenoma), kidney, epidermis, liver, lung (e.g. adenocarcinoma, small cell lung cancer and non-small cell lung carcinomas), oesophagus, gall bladder, ovary, pancreas (e.g; exocrine pancreatic carcinoma), stomach, cervix, thyroid, nose, head and neck, prostate, and skin (e.g. squamous cellcarcinoma). Other examples of cancers that may be treated with a compound ofthe present disclosure include hematopoietic tumours of lymphoid e (e.g. leukemia, acute lymphocytic leukemia, mantle cell lymphoma, chronic lymphocytic leukaemia, B-cell lymphoma(such as diffuse large B cell - lymphoma), T-cell lymphoma, multiple myeloma, Hodgkin’s lymphoma, non-Hodgkin’s lymphoma, hairy cell lymphoma, and t‘s ma; poietic tumours of myeloid lineage, for example acute and chronic myelogenous leukemias, myelodysplastic syndrome, and promyelocytic leukemia. Other cancers include thyroid follicular cancer; a tumour nchymal origin, for example fibrosarcoma or habdomyosarcoma; a tumour ofthe central or peripheral s system, for example astrocytoma, lastoma, glioma or schwannoma; neuroendocrine cancer; melanoma; prostate cancer; ovarian cancer; id cancer; seminoma; teratocarcinoma; osteosarcoma; xeroderma pigmentosum; retinoblastoma; keratoctanthoma; thyroid follicular cancer; and Kaposi's sarcoma.

One group of cancers includesihuman breast cancers (e.g. ER positive breast cancer, Her2 positive breast cancer, PI3K mutated breast cancer, primary breast tumours, node-negative breast , invasive duct adenocarcinomas of the breast, non- endometrioid breast cancers); and endometrial cancers. Another sub-set of cancers wherein compounds having CDK4/6 and/or PI3K inhibitory activity may be of particular therapeutic benefit ses glioblastoma multiforme, T cell ALL, sarcomas, familial melanoma and melanoma.

W0 2013(006532 The combination of the t disclosure could also be useful in the treatment of viral infections, for e herpes Virus, pox virus, Epstein-Barr virus, Sindbis Virus, adenovirus, HIV, HPV, HCV and HCMV; prevention ofAIDS developmentin HIV- infected individuals; chronic inflammatory diseases, for example systemic lupus erythematosus, autoirmnune mediated glomerulonephritis, rheumatoid arthritis, psoriasis, inflammatory bowel e, and autoimmune diabetes mellitus; vascular diseases for example cardiac hypertrophy, restenosis, atherosclerosis; neurodegenerative disorders, for example Alzheimer’s disease, AIDS-related dementia, Parkinson’s disease, amyotropic lateral sclerosis, retinitis pigmentosa, spinal muscular atropy and cerebellar degeneration; ulonephritis; myelodysplastic syndromes, ic injury associated myocardial infarctions, stroke and reperfusion injury, arrhythmia, atherosclerosis, toxin- induced or alcohol related liver diseases, haematological diseases, for example, c anemia and aplastic anemia; degenerative diseases of the musculoskeletal system, for example, orosis and arthritis, aspirin-senstive rhinosinusitis, cystic fibrosis, multiple sclerosis, kidney diseases, ophthalmic diseases including age related macular degeneration, uveitis, and cancer pain.

The phrase aceutically acceptable” refers to molecular entities and compositions that are physiologically tolerable and do not typically produce an allergic or similar untoward reaction, such as gastric upset, dizziness and the like, when administered to a human. Preferably, as used herein, the term “pharmaceutically acceptable” means approved by a regulatory agency of the Federal or a state government or listed in the US. Pharmacopeia or other generally recognized pharmacopeia for use in s, and more particularly in humans.

The term “carrier” refers to a diluent, adjuvant, excipient, or vehicle with which the nd is stered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those ofpetroleum, animal, ble or synthetic origin, such as peanut oil, n oil, mineral oil, sesame oil and the like. Water. or aqueous solution saline solutions and aqueous dextrose and glycerol ons are preferably employed as carriers, particularly for inj ectable solutions. Suitable pharmaceutical carriers are described in gton's Pharmaceutical Sciences” by E. W. Martin.

The phrase “therapeutically effective amount” is used herein to mean an amount sufficient to reduce by at least about 15 t, preferably by at least 50 percent, more preferably by at least 90 percent, and most preferably prevent, a clinically significant deficit in the activity, function and response of the host. Alternatively, a therapeutically effective amount is sufficient to cause an improvement in a clinically significant condition/symptom in the host.

“Agent” refers to all materials that may be used to prepare pharmaceutical and stic compositions, or that may be compounds, c acids, polypeptides, fragments, isoforms, variants, or other materials that may be used ndently for such purposes, all in ance with the present disclosure.

The present disclosure includes all pharmaceutically acceptable isotopically-labeled compounds ofthe disclosure, i.e. compounds of a (I), wherein one or more atoms are replaced by atoms having the same atomic number, but an atomic mass or mass number ent from the atomic mass or mass number usually found in .

Examples of isotopes suitable for inclusion in the nds of the disclosure ses isotopes ofhydrogen, such as 2H and 3H, carbon, such as 11C, 13C and 14C, chlorine, such as 36Cl, fluorine, such as 18F, iodine, such as 123I and 125I, nitrogen, such as ’ 13N and 15N, oxygen, such as 15O, 17O and 18O, phosphorus, such as 32F, and sulphur, such as 358.

Certain isotopically-labelled compounds of Formula (I), for example, those incorporating a radioactive isotope, are useful in drug and/or substrate tissue bution studies. The radioactive isotopes tritium, 1'. e. 3H, and carbon-l4, z'. e. 14C, are particularly useful for this purpose in View of their ease of incorporation and ready means of detection.

Substitution with heavier isotopes such as deuterium, z‘. e. 2H, may afford certain therapeutic advantages resulting from greater metabolic stability, for example, increased in vivo half-life or reduced dosage requirements, and hence may be preferred in some circumstances.

Substitution with positron emitting isotopes, such as 11C, 18F, 15O and 13N, can be useful in Positron Emission Topography (PET) studies for examining substrate receptor occupancy.

Isotopically-labeled compounds of Formula (I) can generally ared by conventional techniques known to those skilled in the art or by processes analogous to those described in the accompanying Examples and Preparations using an appropriate isotopically-labeled reagents in place of the non—labeled reagent previously employed.

Compound A can be synthesized, for example, as described in W02010/020675 or Compound Bl can be synthesized, for example, as described in W02007/084786.

Compound B2 can be synthesized, for e, as described in W02010/029082.

EXAMPLES Potential synergistic ctions between nd A and Compound B lor BZ combinations were assessed relative to the Loewe additivity model using CHALICE software, via a synergy score calculated from the differences between the observed and Loewe model values across the response . Briefly, 9 titrating concentration ranging from 20 MM diluted serially three folds for nd A and 10 uM diluted serially 3 folds for Compound B1 or B2, including 0 uM, were used. In a 96 well plate, the 9 concentration points for'each agent were mixed‘in a matrix , generating 81 combinations. This plate was used to treat MDA-MB—453 cells, and the resulting tion values were used by CHALICE software to generate Inhibition and ADD Excess Inhibition matrices, as well as the isobolograms. A more detailed explanation of the technique and calculation can be found in Lehar et al. “Synergistic drug combinations e therapeutic selectivity”, Nat. hnol. 2009, July; 27(7), 659-666, which is hereby incorporated by reference.

As illustrated by Figure 1, inhibition matrix shows the actual inhibition observed by the CTG assay at the respective concentrations of the compounds. ADD Excess inhibition shows the excess tion observed over the inhibition predicted by the Loewe additivity model. In addition to the matrices, one can Use isobolograms to observe ' synergy. The inhibition level for each isobologram was chosen manually so as to observe W0 2013f006532 PCT/U82012/045199 the best synergistic effects. Isobologram was generated with Compound A concentrations shown on the x-axis and Compound B1 or BZ concentrations shown on the y-axis. A ht line connecting the Compound A and the Compound B1 or B2 concentrations which produce the chosen level of inhibition represented growth tions that were strictly additive for the combinations. Plots placed below the line of additivity (more growth inhibition) represented synergistic growth inhibitions, while plots above the line of additivity (less growth inhibition) represented antagonistic growth inhibitions.

Synergic interaction is observed for the ation of Compound A and - Compound B1 or B2 in the MDA—MB—453 cells.

Example 2 Potential synergistic interactions between Compound A and Compound B1 or B2 combinations were assessed relative to the Loewe additivity model using CHALICE software, via a synergy score calculated from the ences between the observed and Loewe model values across the response . Briefly, 9 titrating concentration ranging from 20 MM diluted serially three folds for Compound A and 20 uM diluted serially 3 folds for nd B1 or B2, ing 0 uM, were used. In a 96 well plate, the 9 concentration points for each agent were mixed in a matrix format, generating 81 combinations. This plate was used to treat breast cancer HGT-116 cells, and the resulting inhibition values were used by CHALICE software to generate Inhibition and ADD Excess tion es, as well as the isobolograms. A more detailed explanation of the" technique and calculation can be found in Lehar et a1. “Synergistic drug combinations improve eutic selectivity”, Nat. Biotechnol. 2009, July; 27(7), 659—666, which is hereby orated by reference.

As illustrated by Figure 2, inhibition matrix shows the actual inhibition observed by the CTG assay at the respective concentrations of the compounds. ADD Excess inhibition shows the excess inhibition ed over the inhibition predicted by the Loewe additivity model. In addition to the matrices, one can use isobolograms to observe synergy. The inhibition level for each isobologram was chosen manually so as to observe the best synergistic effects. Isobologram was generated with Compound A concentrations PCT/U82012/045199 shown on the x-axis and Compound B1 or B2 concentrations shown on the y-axis. A straight line connecting the Compound A and the Compound B1 or B2 concentrations which produce the chosen level of inhibition represented growth inhibitions that were strictly additive for the, ations. Plots placed below the line of additivity (more growth inhibition) represented synergistic growth tions, while plots above the line of additivity (less growth inhibition) represented antagonistic growth tions.

Synergic interaction is observed for the combination of Compound A and Compound B1 or B2 in the HGT-116 cells.

- Example 3 Potential istic interactions between Compound A and nd B1 or B2 combinations were ed relative to the Loewe additivity model using CHALICE software, via a synergy score calculated from the differences between the observed and Loewe model values across the response matrix. Briefly, 9 titrating tration ranging from 20 uM diluted serially three folds for Compound A and 20 uM d serially 3 folds for Compound B1 or B2, including 0 uM, were used. In a 96 well plate, the 9 concentration points for each agent were mixed in a matrix format, ting 81 combinations. This plate was used to treat ER positive breast cancer MCF-7 cells, and the resulting tion values were used by CHALICE re to generate Inhibition and ADD Excess Inhibition matrices, as well as the isobolograms. A more detailed explanation ofthe technique and calculation can be found in Lehar et al. “Synergistic drug combinations improve therapeutic selectivity”, Nat. Biotechnol. 2009, July; 27(7), 659-666, whichsis hereby incorporated by reference.

As illustrated by Figure 3, inhibition matrix shows the actual inhibition observed by the BrdU assay at the respective concentrations of the compounds. ADD Excess inhibition shows the excess inhibition observed OVCI‘ the tionpredicted by the Loewe additivity model. In addition to the matrices, one can use isobolograms to observe synergy. The inhibition level for each isobologram was chosen manually so as to observe the best synergistic effects. Isobologram was generated with Compound A concentrations shown on the x-axis and Compound B1 or B2 concentrations shown on the y—axis. A PCT/U82012/045199 straight line connecting the Compound A and the Compound B1 or B2 concentrations which produce the chosen level of inhibition represented growth inhibitions that were strictly additive for the ations. Plots placed below the line of additivity (more growth inhibition) represented istic growth inhibitions, while plots above the line of additivity (less growth-inhibition) represented antagonistic growth inhibitions.

Synergic interaction is observed for the combination of Compound A and Compound B1 or B2 in the MCF-7 cells.

Example 4 Potential synergistic ctions between Compound A and Compound B2 combinations were ed relative to the Loewe additivity model using CHALICE software, via a synergy score calculated from the differences between the observed and Loewe model values across the response matrix. Briefly, 9 titrating concentration ranging from 20 uM d serially three folds for Compound A and 20 uM diluted serially 3 folds for Compound B2, including 0 uM, were used. In a 96 well plate, the 9 concentration points for each agent were mixed in a matrix , generating 81 combinations. This plate was used to treat ER positive breast cancer T47-D cells, and the resulting inhibition values were used by CHALICE re to generate Inhibition and ADD Excess Inhibition matrices, as well as the ograms. A more detailed explanation of the technique and calculation can be found in Lehar et a1. “Synergistic drug combinations improve therapeutic selectivity”, Nat. Biotechnol. 2009, July; 27(7), 659-666, which is hereby incorporated by reference.

As illustrated by Figure 4, inhibition matrix shows the actual inhibition observed by the BrdU assay at the respective concentrations of the nds. ADD Excess inhibition shows the excess inhibition ed over the inhibition predicted by the Loewe vity model. In addition to the matrices, one can use isobolograms to observe synergy. The inhibition level for each isobologram was chosen manually so as to observe the best synergistic effects. Isobologram was generated with Compound A concentrations shown on the x-axis and Compound B2 concentrations shown on the y-axis. A straight line ting the Compound A and the Compound 82 concentrations which produce PCT/U82012/045199 the chosen level of inhibition represented growth inhibitions that were strictly additive for the combinations. Plots placed below the line of additivity (more growth inhibition) represented synergistic growth inhibitions, while plots above the line of additivity (less grth inhibition) represented antagonistic growth inhibitions.

Synergic ction is observed for the combination of Compound A and Compound B2 in the T47-D cells.

Claims (1)

What is claimed is:

1. A combination comprising a first agent that is a cyclin ent kinase 4 or cyclin dependent kinase 6 (CDK