IOX-2 is a potent, cell-permeable and selective inhibitor of HIF-1α prolyl hydroxylase-2 (PHD2) (IC₅₀ = 21 nM). It displays over 100-fold selectivity for PHD2 over factor inhibiting HIF-1 (FIH-1) and histone demethylases JMJD2A, JMJD2C, JMJD2E and JMJD3.