We were interested if patient-derived BCP-ALL xenografts in zebrafish could be used to assist selection of promising targeted drugs in refractory or relapse cases, and began with the BCL2 inhibitor, venetoclax, for which treatment response in the ALL-ZeFiX assay correlated with responses in two patients with BCP-ALL receiving venetoclax treatment on our ward to date. Here, OPN1SW is linked to acute lymphoblastic leukemia.