Purity >98%. Obatoclax is an antagonist of Bcl-2 family members containing four Bcl-2 homology domains, including Bcl-2, Bcl-W, Bcl-xL, and Mcl-1 (Kd = ~500 nM). It prevents the interaction of these pro-survival proteins with Bax or Bak, thereby inducing apoptosis with up-regulation of Bim, induced cytochrome c release, and activation of caspase-3. Obstoclax also induces autophagy in mouse embryo fibroblasts and in HeLa cells. This compound inhibits the growth of cancer cell lines and primary cancer isolates.