[CAS NO. 1227962-62-0]  Marinopyrrole A (Maritoclax)

Maritoclax induces Mcl-1 degradation via the proteasome system, which is associated with the pro-apoptotic activity of maritoclax. Maritoclax selectively kills Mcl-1-dependent, but not Bcl-2- or Bcl-XL-dependent, leukemia cells and markedly enhances the efficacy of ABT-737 against hematologic malignancies, including K562, Raji, and multidrug-resistant HL60/VCR, by ∼60- to 2000-fold at 1-2 μM. Maritoclax blocks the interaction between a biotin-labeled Bim-BH3 peptide and GST-Mcl-1 in a dose-dependent manner with an IC50 value of 10.1 μM, while it does not inhibit the binding of Bim-BH3 peptide to GST-Bcl-XL at concentrations up to 80 μM. Maritoclax induces caspase-3 activation by degradation of Mcl-1 protein. Treatment with maritoclax markedly reduces the half-life of Mcl-1 to ∼0.5 h as compared with nearly 3 h in control cells. Maritoclax has no apparent effect on Mcl-1 (Ser159/Thr163) phosphorylation, suggesting that maritoclax induces phosphorylation-independent Mcl-1 degradation. Marinopyrrole A has potent concentration-dependent bactericidal activity against clinically relevant hospital- and community-acquired MRSA strains. Marinopyrrole A shows limited toxicity to mammalian cell lines (at >20× MIC). Maritoclax sensitivity is cell type specific. It is not effective in HeLa, HEK293, or MEF cells. Maritoclax is not a substrate for p-gp mediated drug efflux.