This report presents a case of B-ALL with MLL-r who developed extramedullary relapse (EMR) after undergoing allo-HCT, and was treated with the VCA regimen—a combination of venetoclax (a Bcl-2 inhibitor), chidamide (a selective histone deacetylase inhibitor), and azacitidine (a DNA demethylating agent)—which resulted in a CR. This evidence concerns the gene BCL2 and acute lymphoblastic leukemia.