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

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.