BCL2L1 and Thrombocytopenia: However, it is unlikely that PZ will be totally devoid of platelet toxicity, because it retains a high binding affinity to Bcl-xl (Ki = 1.90 nM for PZ vs. Ki = 1.53 nM for ABT263), and thus can still function as a Bcl-xl inhibitor that could potentially induce thrombocytopenia if the concentrations of PZ reach a high level in blood.