ABT-199 (venetoclax) is a next-generation BH3 mimetic designed to spare BCL-xL (Souers et al., 2013); however, despite the obvious benefit of this drug in avoiding thrombocytopenia, its utility may largely be dictated by a cancer's propensity to rely on BCL-2 over BCL-xL for survival. The gene discussed is BCL2L1; the disease is cancer.