Crystallographic Investigation and Selective Inhibition of Mutant Isocitrate Dehydrogenase

Mutations in isocitrate dehydrogenase (IDH), a key Enzyme in the tricarboxylic acid cycle, have recently been found in ~75% glioma and ~20% acute myeloid leukemia. Different from the wild-type Enzyme, mutant IDH1 catalyzes the reduction of α-ketoglutaric acid to D-2-hydroxyglutaric acid. Strong evidence has shown mutant IDH1 represents a novel target for this type of Cancer. We found two 1-hydroxypyridin-2-one compounds that are potent inhibitors of R132H and R132C IDH1 mutants with K_i values as low as 120 nM. These compounds exhibit >60-fold selectivity against wild-type IDH1 and can inhibit the production of D-2-hydroxyglutaric acid in IDH1 mutated cells, representing novel chemical probes for Cancer biology studies. We also report the first inhibitor-bound crystal structures of IDH1(R132H), showing these inhibitors have H-bond, electrostatic and hydrophobic interactions with the mutant Enzyme. Comparison with the substrate-bound IDH1 structures revealed the structural basis for the high Enzyme selectivity of these compounds.

Enzyme inhibition; Gene mutation; isocitrate dehydrogenase; protein crystallography.