Inhibition of Mutated Isocitrate Dehydrogenase 1 in Cancer

Background: R132H mutation of isocitrate dehydrogenase 1 (IDH1) is found in similar to 75% of low-grade gliomas and secondary glioblastomas as well as in several other types of cancer. More chemotypes of inhibitors of IDH1(R132H) are therefore needed. Objective: The study aimed to develop a new class of IDH1(R132H) inhibitors as potent antitumor agents. Method: A biochemical assay was developed to find inhibitors of IDH1(R132H) mutant enzyme. Chemical synthesis and structure-activity relationship studies were used to find compounds with improved potency. Antitumor activities of selected compounds were evaluated. Results: A series of aromatic sulfonamide compounds was found to be novel, potent inhibitors of IDH1(R132H) with K-i values as low as 0.6 mu M. Structure-activity relationships of these compounds are discussed. Enzyme kinetics studies showed that one compound is a competitive inhibitor against the substrate alpha-KG and a non-competitive inhibitor against the cofactor NADPH. Several inhibitors were found to have no activity against wild-type IDH1, showing a high selectivity. Two potent inhibitors exhibited strong activity against proliferation of BT142 glioma cells with IDH1 R132H mutation, while these compounds did not significantly affect the growth of glioma cells without IDH1 mutation. Conclusion: This novel series of IDH1(R132H) inhibitors have potential to be further developed for the treatment of glioma with IDH1 mutation.