A-1155463 Hydrochloride, is a potent and selective BCL-XL inhibitor with in vivo activity. A-1155463 is a proteolytically stable, cell-permeable and high affinity BH3 mimetic Ligand of BCL protein BCL-XL, binding to the target potently and selectively with a Ki value of <0.01nM (<10 pM), highly selective against closely related proteins of BCL-2 (Ki = 74nM, >7000-fold selectivity), BCL-W (Ki = 8 nM, >800-fold selectivity), and MCL-1 (Ki >444nM, >40000-fold selectivity). A-1155463, together with A-1331852 , represent the first-in-class small molecule BCL-XL selective inhibitors achieving clear-on-target in vivo activity with high potency and selectivity. In living cells, A-1155463, as anticipated, experts an effort to disrupt the tight-binding BCL-XL-BIM, but not BCL-2–BIM, complexes, killi
