[CAS NO. 803712-79-0]  Obatoclax Mesylate (GX15-070)

Obatoclax completely inhibits Bak recovery of Mcl-1 at 5 μM in SK-Mel5 cells and overcomes resistance to ABT-373-induced apoptosis conferred by Mcl-1 in KB/Bcl-2 cells. Obatoclax is a BH3 mimetic which binds to a broad spectrum of Bcl-2 family members, including Bcl-2, Bcl-xL, and Mcl-1. Obatoclax uniquely displaces BH3 domains by activation of the pocket of Mcl-1 followed by a triggering of apoptosis mediated by oligomerization of Bak and release of cytochrome c. Obatoclax is sensitive to Bcl-xL in cell lines lacking it or showing low expression. It shows low cytotoxicity to Mcl-1, Bcl-2, and Bcl-xL in all the strongly-expressed cell lines. Obatoclax inhibits multiple myeloma (MM) cell lines (KMS12PE, KMS18, MY5, etc.) with IC50 values ranging from 52 to 1100 nM and the inhibition is umimpaired even in the presence of IL-6 or IGF-1, which are resistance to cytotoxic agents, at a concentration of 150 nM. Obatoclax enhances the antimyeloma activity induced by melphalan, dexamethasone, or bortezomib. Obatoclax potentiates TRAIL (tumor necrosis factor-related apoptosis-inducing ligand)-mediated apoptosis by unsequestering Bak and Bim from Bcl-2/Bcl-xL or Mcl-1 proteins in PANC-1 and BxPC-3 cells.