BCL2 and B-cell chronic lymphocytic leukemia: We also identified a previously non-reported nonsynonymous BCL2 mutation (BCL2A113P) at an allelic frequency of 49.3%, which in contrast to previously noted mutations was present at an allelic frequency indicating that nearly all the CLL cells of this patient expressed this mutant allele of BCL2. Like the other previously identified mutations in BCL2 associated with venetoclax resistance, this mutation encodes a residue close to the site bound by venetoclax, thereby potentially mitigating the capacity of this drug to bind and inhibit BCL2.