MCL1 and cancer: ABT-737 [3], the most well-known member of a class of Bcl-2-family targeting compounds, and its orally active analog ABT-263 [4], have activity as single agents in a subset of cancers (including multiple myeloma and small-cell lung cancer) that rely on Bcl-2/Bcl-xL, but not Mcl-1, for survival.