A Fragment-Derived Clinical Candidate for Antagonism of X-Linked and Cellular Inhibitor of Apoptosis Proteins: 1-(6-[(4-fluorophenyl)methyl]-5-(hydroxymethyl)-3,3-dimethyl-1h,2h,3h-py Rrolo[3,2-B]pyridin-1-yl)-2-[(2r,5r)-5-methyl-2-([(3r)-3-methylmorpholin -4-yl]methyl)piperazin-1-yl]ethan-1-one (ASTX660)