(1R)-IDH889 is the isomer of IDH889 , and can be used as an experimental control. IDH889 is an orally available, brain penetrant, allosteric and mutant specific inhibitor of isocitrate dehydrogenase 1 ( IDH1 ). IDH889 has potent selectivity for IDH1 R132* mutations, with IC 50 s of 0.02 μM, 0.072 μM and 1.38 μM for IDH1 R132H , IDH1 R132C and IDH1 wt , respectively. IDH889 shows potent cellular inhibition of R-2-hydroxyglutarate (2-HG) production with an IC 50 of 0.014 μM.