Safety and Efficacy of Blinatumomab in Combination With a Tyrosine Kinase Inhibitor for the Treatment of Relapsed Philadelphia Chromosome-positive Leukemia

Micro-Abstract The prognosis of patients with relapsed refractory Philadelphia chromosome–positive acute leukemia is considered poor. The combination of blinatumomab and a TKI resulted in high overall response rates among 13 patients. These results are promising and this strategy may minimize the use of chemotherapy in this setting. Objective The treatment of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia has been revolutionized with the introduction of tyrosine kinase inhibitors (TKIs) and the combination of these agents with chemotherapy. Blinatumomab is a bispecific anti-CD3/CD19 monoclonal antibody with clinical activity as single-agent in the relapsed setting and independent of BCR-ABL1 mutational status, including T315I. The combination of blinatumomab with a TKI may further improve outcomes for this high-risk population, including higher eradication of minimal residual disease and minimize the use of chemotherapy. Patients and Methods We retrospectively studied 12 adults with relapsed/refractory Ph+ acute lymphoblastic leukemia (n = 9) and chronic myeloid leukemia in blast crisis (n = 3), treated with the combination blinatumomab and a TKI (ponatinib, n = 8; dasatinib, n = 3; bosutinib, n = 1). All patients have previously failed at least 1 line of chemotherapy, including allogeneic stem cell transplantation, and 1 class of TKIs. Patients were treated for either overt hematologic relapse (n = 6) or persistent minimal residual disease following other regimens (n = 6). Results The complete hematologic, cytogenetic, and molecular response rates were 50% (3/6), 71% (5/7), and 75% (9/12), respectively. Two cases of grade 2 cytokine release syndrome were observed, all of which resolved with steroids and tocilizumab. No cardiovascular adverse events were encountered. With a median follow-up of 8 months, the median survival was not reached; the 6-month and 1-year overall survival rates were 73%. Conclusions The combination of blinatumomab with TKI is safe and effective in patients with relapsed/refractory Ph+ disease. Prospective studies are warranted.