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As a continuation of our efforts to discover and develop apoptosis inducing N-methyl-4-(4-methoxyanilino)quinazolines as novel anticancer agents, we explored substitution at the 5-, 6-, 7-positions of the quinazoline and replacement of the quinazoline by other nitrogen-containing heterocycles. A small group at the 5-position was found to be well tolerated. At the 6-position a small group like an amino was preferred. Substitution at the 7-position was tolerated much less than at the 6-position. Replacing the carbon at the 8-position or both the 5- and 8-positions with nitrogen led to about 10-fold reductions in potency. Replacement of the quinazoline ring with a quinoline, a benzo[d][1,2,3]triazine, or an isoquinoline ring showed that the nitrogen at the 1-position is important for activity, while the carbon at the 2-position can be replaced by a nitrogen and the nitrogen at the 3-position can be replaced by a carbon. Through the SAR study, several 5- or 6-substituted analogs, such as 2a and 2c, were found to have potencies approaching that of lead compound N-(4-methoxyphenyl)-N,2-dimethylquinazolin-4-amine (1g, EP128495, MPC-6827, Azixa)., (2010 Elsevier Ltd. All rights reserved.)

As a continuation of our studies of apoptosis inducing 9-oxo-9H-fluorene-1-carboxamides as potential anticancer agents, we explored modification of the 9-oxo-9H-fluorene ring. SAR studies showed that most changes to the 9-oxo-9H-fluorene ring were not well tolerated, except the 9H-fluorene (2b) and dibenzothiophene (2d) analogs, which were about twofold less active than the 9-oxo-9H-fluorene analog 2a. Significantly, introduction of substitutions at the 7-position of the 9-oxo-9H-fluorene ring led to compounds 5a-5c with improved activity. Compound 5a was found to have EC(50) values of 0.15-0.29 microM against T47D, HCT116, and SNU398 cells, about fivefold more potent than the original lead 2a. As opposed to the original lead compound 2a, compounds 5a-5b were active in a tubulin inhibition assay, indicating a change of mechanism of action. The potent azido analog 5c could be utilized for target identification., (Copyright (c) 2009. Published by Elsevier Ltd.)

As a continuation of our efforts to discover and develop the 3-aryl-5-aryl-1,2,4-oxadiazole series of apoptosis inducers as potential anticancer agents, we explored substitutions at the 2- and 3-positions of the 3-aryl group to improve the aqueous solubility properties and identify development candidates. A small substitution such as methyl or hydroxymethyl at the 2-position was well tolerated. This modification, in combination with a 3-substituted furan ring as the 5-aryl group, resulted in 4g and 4h, which have improved solubility properties. Compound 4g was found to have good in vivo efficacy in animal studies via intravenous administration.

As a continuation of our efforts to discover and develop the apoptosis inducing 1-benzoyl-3-cyanopyrrolo[1,2-a]quinolines as potential anticancer agents, we explored substitutions at the 4-, 5-, 6-, 7- and 8-positions of pyrrolo[1,2-a]quinoline. SAR studies showed that substitution at the 6-position by a small group such as Cl resulted in potent compounds. Substitutions at the 5- and 8-positions were tolerated while substitutions at the 4- and 7-position led to inactive compounds. Several compounds, including 2c, 3a, 3b and 3f, were found to be highly active against human breast cancer cells T47D with EC(50) values of 0.053-0.080microM, but much less active against human colon cancer cells HCT116 and hepatocellular carcinoma cancer cells SNU398 in the caspase activation assay. Compound 3f also was found to be highly active with a GI(50) value of 0.018microM against T47D cells in a growth inhibition assay.

We report the discovery of N-((benzo[d][1,3]dioxol-5-yl)methyl)-6-phenylthieno[3,2-d]pyrimidin-4-amine (2a) as an apoptosis inducer using our proprietary cell- and caspase-based ASAP HTS assay, and SAR study of HTS hit 2a which led to the discovery of 4-anilino-N-methylthieno[3,2-d]pyrimidines and 4-anilino-N-methylthieno[2,3-d]pyrimidines as potent apoptosis inducers. Compounds 5d and 5e were the most potent with EC(50) values of 0.008 and 0.004microM in T47D human breast cancer cells, respectively. Compound 5d was found to be highly active in the MX-1 breast cancer model. Functionally, compounds 5d and 5e both induced apoptosis through inhibition of tubulin polymerization.

N-(2-Methylphenyl)-9-oxo-9H-fluorene-1-carboxamide (2a) was identified as a novel apoptosis inducer through our caspase- and cell-based high-throughput screening assay. Compound 2a was found to be active with sub-micromolar potencies for both caspase induction and growth inhibition in T47D human breast cancer, HCT116 human colon cancer, and SNU398 hepatocellular carcinoma cancer cells. It arrested HCT116 cells in G(2)/M followed by apoptosis as assayed by the flow cytometry. Structure-activity relationship (SAR) studies of the carboxamide group identified the lead compound N-(2-(1H-pyrazol-1-yl)phenyl)-9-oxo-9H-fluorene-1-carboxamide (6s). Compound 6s, with increased aqueous solubility, was found to retain the broad activity in the caspase activation assay and in the cell growth inhibition assay with sub-micromolar EC(50) and GI(50) values in T47D, HCT116, and SNU398 cells, respectively.

We report the discovery of a series of substituted N'-(2-oxoindolin-3-ylidene)benzohydrazides as inducers of apoptosis using our proprietary cell- and caspase-based ASAP HTS assay. Through SAR studies, N'-(4-bromo-5-methyl-2-oxoindolin-3-ylidene)-3,4,5-trimethoxybenzohydrazide (3g) was identified as a potent apoptosis inducer with an EC(50) value of 0.24microM in human colorectal carcinoma HCT116 cells, more than a 40-fold increase in potency from the initial screening hit N'-(5-bromo-2-oxoindolin-3-ylidene)-3,4,5-trimethoxybenzohydrazide (2a). Compound 3g also was found to be highly active in a growth inhibition assay with a GI(50) value of 0.056microM in HCT116 cells. A group of potentially more aqueous soluble analogs were prepared and found to be highly active. Among them, compound 4e incorporating a methyl piperazine moiety was found to have EC(50) values of 0.17, 0.088 and 0.14microM in human colorectal carcinoma cells HCT116, hepatocellular carcinoma cancer SNU398 cells and human colon cancer RKO cells, respectively. Compounds 3g and 4e were found to function as inhibitors of tubulin polymerization.

As a continuation of our efforts to discover and develop the apoptosis inducing 4-anilino-2-(2-pyridyl)pyrimidines as potential anticancer agents, we explored replacing the 2-pyridyl group by other aryl groups. SAR studies showed that the 2-pyridyl group can be replaced by a 3-pyridyl, 4-pyridyl and 2-pyrazinyl group, and that the SAR for the anilino group was similar to that of the 2-pyridyl series. However, replacement of the 2-pyridyl group by a phenyl group, a 3,5-dichloro-4-pyridyl group, or a saturated ring led to inactive compounds. Several potent compounds, including 2f, 3d, 3j and 4a, with EC(50) values of 0.048-0.024 microM in the apoptosis induction assay against T47D cells, were identified through the SAR studies. In a tubulin polymerization assay, compound 2f, which was active against all the three cell lines tested (T47D, HTC116 and SNU398), inhibited tubulin polymerization with an IC(50) value of 0.5 microM, while compound 2a, which was active against T47D cells but not active against HTC116 and SNU398 cells, was not active in the tubulin assay at up to 50 microM.

1-Benzoyl-3-cyanopyrrolo[1,2-a]quinoline (2a) was identified as a novel apoptosis inducer through our caspase- and cell-based high-throughput screening assay. Compound 2a had good activity against several breast cancer cell lines but was much less active against several other cancer cell lines. SAR studies of 2a found that substitution at the 4-position of the 1-benzoyl group was important for activity. Replacing the 3-cyano group by an ester or ketone group led to inactive compounds. Interestingly, 4-substituted analogs such as 1-(4-(1H-imidazol-1-yl)benzoyl)-3-cyanopyrrolo[1,2-a]quinoline (2k) were found to be broadly and highly active in the caspase activation assay as well as in the cell growth inhibition assay with low nM EC(50) and GI(50) values in human breast cancer cells T47D, human colon cancer cells HCT116, and hepatocellular carcinoma cancer cells SNU398. Compound 2a was found not to inhibit tubulin polymerization up to 50 microM, while 2k was found to inhibit tubulin polymerization with an IC(50) value of 5 microM, indicating that certain substituents at the 4-position of the 1-benzoyl group can change the mechanism of action.

We report the discovery of a series of (naphthalen-4-yl)(phenyl)methanones as potent inducers of apoptosis using our proprietary cell- and caspase-based ASAP HTS assay. Through SAR studies, a group of N-methyl-N-phenylnaphthalen-1-amines also were identified as potent inducers of apoptosis. (1-(Dimethylamino)naphthalen-4-yl)(4-(dimethylamino)phenyl)methanone (2a), one of the most potent analogs, had EC(50) values of 37, 49 and 44nM in T47D, HCT116 and SNU398 cells, respectively. Compound 2a also was highly active in a growth inhibition assay with an GI(50) value of 34nM in T47D cells. Functionally, compound 2a arrested HCT116 cells in G(2)/M followed by induction of apoptosis and inhibited tubulin polymerization.

As a continuation of our efforts to discover and develop the apoptosis inducing 4-aryl-4H-chromenes as potential anticancer agents, we explored the removal of the chiral center at the 4-position and prepared a series of 4-aryl-2-oxo-2H-chromenes. It was found that, in general, removal of the chiral center and replacement of the 2-amino group with a 2-oxo group were tolerated and 4-aryl-2-oxo-2H-chromenes exhibited SAR similar to 4-aryl-2-amino-4H-chromenes. The 4-aryl-2-oxo-2H-chromenes with a N-methyl pyrrole fused at the 7,8-positions were highly active with compound 2a having an EC(50) value of 13 nM in T47D cells. It was found that an OMe group was preferred at the 7-position. 7-NMe(2), 7-NH(2), 7-Cl and 7,8 fused pyrido analogs all had low potency. These 4-aryl-2-oxo-2H-chromenes are a series of potent apoptosis inducers with potential advantage over the 4-aryl-2-amino-4H-chromenes series via elimination of the chiral center at the 4-position.

As a continuation of our efforts to discover and develop apoptosis inducing 4-aryl-4H-chromenes as novel anticancer agents, we explored modifications at the 2- and 3-positions. It was found that replacement of the 3-cyano group by an ester, including methyl and ethyl ester, resulted in >200-fold reduction of activity. Conversion of the 2-amino group into an amide or urea resulted in 4- to 10-fold drop of activity. Similarly, converting the 2-amino group into a hydrogen resulted in 4- to 10-fold reduction of activity. Compound 3d was highly active with an EC(50) value of 29 nM and a GI(50) value of 6 nM in T47D cells. Importantly, the 2-H analog 3d was found to be much more stable under acidic conditions compared to the 2-NH(2) analog 3b, suggesting that 2-H analogs might have better bioavailability than the 2-NH(2) analogs.

As a continuation of our SAR studies of dipeptidyl aspartyl-fmk as caspase inhibitors, we explored the replacement of the P(2) amino acid by a 2-aminoaryl acid or other non-natural amino acids. Several of these compounds, such as 6l and 6p, were found to have good activities with inhibition potencies of around 100 nM in a caspase-3 enzyme assay. EP1113, Z-Val-(2-aminobenzoyl)-Asp-fmk (9b), is identified as a potent broad-spectrum caspase inhibitor with IC(50) values of 6-60 nM in different caspases. EP1113 also has good activity in a cell apoptosis protection assay.

We report the discovery of 5-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-7-(4-methylphenyl)-(E)-2,3,6,7-tetrahydro-1,4-thiazepine (2a) as an inducer of apoptosis using our proprietary cell- and caspase-based HTS assay. Through structure activity relationship (SAR) studies, 5-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-7-(2-methoxy-4-(methylthio)phenyl)-(E)-2,3,6,7-tetrahydro-1,4-thiazepine (5d) was identified as a potent apoptosis inducer with an EC(50) value of 0.08 microM in T47D cells, which was >15-fold more potent than screening hit 2a. Compound 5d also was found to be highly active in a growth inhibition assay with a GI(50) value of 0.05 microM in T47D cells and to function as an inhibitor of tubulin polymerization.

As a continuation of our efforts to discover novel apoptosis inducers as anticancer agents using a cell-based caspase HTS assay, 2-phenyl-oxazole-4-carboxamide derivatives were identified. The structure-activity relationships of this class of molecules were explored. Compound 1k, with EC(50) of 270 nM and GI(50) of 229 nM in human colorectal DLD-1 cells, was selected and demonstrated the ability to cleave PARP and displayed DNA laddering, the hallmarks of apoptosis. Compound 1k showed 63% tumor growth inhibition in human colorectal DLD-1 xenograft mouse model at 50 mpk, bid.

As a continuation of our efforts to discover and develop the apoptosis inducing 4-aryl-4H-chromenes as novel anticancer agents, we explored the SAR of 4-aryl-4H-chromenes with modifications at the 7- and 5-, 6-, 8-positions. It was found that a small hydrophobic group, such as NMe2, NH2, NHEt, and OMe, is preferred at the 7-position. Di-substitution at either the 5,7-positions or the 6,7-positions generally led to a large decrease in potency. Di-substitution at the 7,8-positions, in general, was found to result in potent compounds. 7-NMe2, 7-NHEt, 7-OMe, and 7,8-di-NH2 analogs were found to have similar SAR for the 4-aryl group, and several 7-substituted and 7,8-di-substituted analogs were found to have similar potencies as the lead compound MX58151 (2a) both as caspase activators and inhibitors of cell proliferation.

As a continuation of our SAR studies of dipeptidyl aspartyl-fmk as caspase inhibitors, we explored the replacement of the P2 alpha-amino acid by a peptidomimetic alpha-hydroxy acid. These alpha-carbamoyl-alkylcarbonyl-aspartyl fluoromethylketones were found to be potent caspase inhibitors, and the SAR of these compounds is similar to the corresponding dipeptidyl aspartyl-fmk. MX1153, (S)-3-methyl-2-(phenylcarbamoyl)butanoyl-Asp-fmk, is identified as a potent broad-spectrum caspase inhibitor, and is selective for caspases versus other proteases. MX1153 also has good activity in the cell apoptosis protection assays and is active in the mouse liver apoptosis model.

This article describes the synthesis and biological evaluation of a group of N-protected Val-Asp-fmk as caspase inhibitors. The protecting group was found to contribute to caspase-3 inhibiting activity, and compounds with a large group such as Cbz are more active than compounds with a small group such as Ac. Compounds with more hydrophobic protecting groups were found to be more active in cell apoptosis protection assays, probably due to increased cell permeability. MX1122, 2,4-di-Cl-Cbz-Val-Asp-fmk, is identified as a potent broad-spectrum caspase inhibitor and is selective for caspases versus other proteases, with good activity in the cell apoptosis protection assays as well as good efficacy in the mouse liver apoptosis model.