Ponatinib and prednisolone induce sustained remission in a relapsed case of mixed-phenotype acute leukemia with BCR::ABL1 fusion intolerant to dasatinib

Mixed-phenotype acute leukemia (MPAL) with BCR::ABL1 fusion is a rare leukemia subtype exhibiting both myeloid and lymphoid traits. Standard treatment involves chemotherapy with a tyrosine kinase inhibitor (TKI). However, establishing the optimal treatment strategy for elderly patients with MPAL with BCR::ABL1 fusion is challenging due to their intolerance to intensive chemotherapy. It has not yet been determined whether therapy with a TKI and prednisolone, a combination known to be effective in elderly patients with B-lymphoblastic leukemia with BCR::ABL1 fusion is also safe and effective for MPAL with BCR::ABL1 fusion. Here we report the first example of an elderly patient with MPAL with BCR::ABL1 fusion who was treated successfully with ponatinib and prednisolone. Despite achieving complete response with dasatinib plus chemotherapy, the patient suffered a relapse during the withdrawal of dasatinib and had two episodes of gastrointestinal bleeding attributed to the dasatinib therapy, necessitating therapy discontinuation. The treatment was then switched to a regimen of ponatinib and prednisolone, and the patient achieved and maintained complete molecular remission for over seven years without any serious adverse events. This case suggests that ponatinib, with or without prednisolone, could be a potential salvage option for elderly patients with MPAL with BCR::ABL1 fusion who suffer relapse or are intolerant to dasatinib.