BCL2L1 and Thrombocytopenia: Bcl-XL is an essential antiapoptotic protein in mature platelets, and hence inhibition of Bcl-XL causes thrombocytopenia [16], which has been identified as dose-limiting toxicity in clinical trials with the dual Bcl-2/Bcl-XL inhibitor ABT-263 (navitoclax) [17].