Blinatumomab Treatment in Korean Adult Patients with Relapse/Refractory Acute Lymphoblastic Leukemia

Blinatumomab is a bispecific T- cell engaging antibody construct targeting CD19 on B-cell lymphoblast and has demonstrated the efficacy for relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL). In this study, we evaluated the efficacy and toxicity of blinatumomab monotherapy in Korean patients with relapse/refractory ALL. A total of 40 patients received blinatumomab monotherapy between July 2016 and July 2017 in Korea. Median time to blinatumomab treatment from initial diagnosis was 13.6 months (range 1.3 - 104.7). Twenty-four patients completed induction therapy (2 cycles of blinatumomab), 15 ended in cycle 1 due to disease progression or toxicity, and 1 died in 1 cycle due to infection. Among 39 evaluable patients, 17 patients (42.5%) achieved complete response (CR) or CR with incomplete blood count recovery, and 10 responders underwent subsequent allogenic stem cell transplantation. Nine patients had extramedullary disease at relapse and 3 (33.3%) achieved CR. Median progression free survival (PFS) and overall survival (OS) were 2.8 months and 5.7 months, respectively. Patients responded to blinatumomab had significantly better PFS and OS compare to those who did not. In multivariate analysis, patients with 50% or more of bone marrow blast at relapse and relapse within 12 months after initial diagnosis were significantly associated with poor response to blinatumomab. The most common non-hematologic toxicity was neurologic toxicity. Thirteen patients (32.5%) had neurologic events and severe neurologic events (grade 3-4) occurred in two patients in 2nd cycle of blinatumomab. Severe cytokine release syndrome (grade 3) occurred in 2 patients (5.0%) despite pretreatment with dexamethasone. In conclusion, blinatumomab monotherapy was effective and tolerable in Korean adult patients with relapse/refractory ALL.