(1R)-IDH889 is the inactive isomer of IDH889 (HY-112289), 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 IC₅₀s 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 IC₅₀ of 0.014 μM^[1].