Cell-permeable. A small-molecule pan–Bcl-2 antagonist that mimics BH3-only proteins by binding to multiple antiapoptotic Bcl-2 members. GX15-070 has been shown to overcome Bcl-2–, Bcl-xl–, Bcl-w–, and Mcl-1–mediated resistance to Bax or Bak. It potently interferes with the direct interaction between Mcl-1 and Bak in the intact outer mitochondrial membrane and inhibits the association between Mcl-1 and Bak in intact cells.