For example, the small molecule ABT-737 (and related ABT-263) targeting Bcl-2, Bcl-xL and Bcl-w exhibits dose-limiting thrombocytopenia in treating Bcl-2-dependent chronic lymphocytic leukemia due to excessive inhibition of Bcl-xL, which has a role in platelet development (Mason et al., 2007; Roberts et al., 2012). The gene discussed is BCL2L1; the disease is B-cell chronic lymphocytic leukemia.