Efficacy and safety of ponatinib for patients with Philadelphia chromosome-positive acute lymphoblastic leukemia: a case series from a single institute.

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph + ALL) is an aggressive leukemia that occurs in 20-40% of adult patients. Ph + ALL is caused by the Philadelphia chromosome (Ph), which consists of a t(9;22)(q34;q11) reciprocal translocation leading to the formation of a BCR-ABL1 fusion gene. The disease is treated with targeted therapy comprising ABL1 tyrosine kinase inhibitors (TKIs). Ponatinib is a third generation TKI that demonstrates higher binding affinity for ABL1 than first/second generation TKIs. Although intensive combined immunotherapy with ponatinib greatly improves the prognosis of Ph + ALL, the safety and efficacy profiles of ponatinib in Japanese patients are unclear. This retrospective study investigated five cases of Ph + ALL at a single institute to evaluate safety and efficacy profiles. Three patients achieved a deep molecular response (DMR) following combined intensive treatment with ponatinib as induction chemotherapy. Four patients received consolidative allogenic stem cell transplantation (allo-SCT) during their first complete response. Three of the four experienced early relapse within 100 days; they subsequently received ponatinib, and one of the three achieved a DMR. No patient experienced severe cardiovascular events. This case series suggests that ponatinib at a concentration of least 30 mg exhibits anti-leukemia effects in Japanese patients with Ph + ALL.