A xenograft study investigating the effect of the BCL-2 inhibitor venetoclax, which has clinical efficacy in other settings, demonstrated the poor efficacy of this drug on T-ALL and ETP-ALL xenografts, despite the fact that high BCL-2 expression was positively correlated with a response in KMT2A (MLL)-rearranged and precursor B-ALL xenografts.98 This is most likely the result of high levels of BCL-XL, which is not targeted by venetoclax, indicating the need to concurrently inhibit this pro-survival protein. This evidence concerns the gene BCL2L1 and acute lymphoblastic leukemia.