Discovery of substituted N′-(2-oxoindolin-3-ylidene)benzohydrazides as new apoptosis inducers using a cell- and caspase-based HTS assay

The discovery and SAR studies of substituted N′-(2-oxoindolin-3-ylidene)benzohydrazides as novel and potent apoptosis inducers are reported. 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 0.24 μM 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 0.056 μM 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 0.14 μM 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.