Feasible outcome of blinatumomab followed by allogeneic hematopoietic cell transplantation for adults with Philadelphia chromosome‐negative acute lymphoblastic leukemia in first salvage

In adult patients with relapsed or refractory (R/R) Philadelphia chromosome‐negative (Ph‐negative) B‐cell presursor acute lymphoblastic leukemia (BCP‐ALL), complete remission (CR) and overall survival (OS) rates are poor. We analyzed treatment outcomes and prognostic factors for 32 adult patients with R/R Ph‐negative BCP‐ALL who received blinatumomab at first salvage. Patients who achieved CR proceeded to allogeneic hematopoietic cell transplantation (allo‐HCT). At the time of blinatumomab treatment, 11 patients (34.3%) were primary refractory, 10 (31.4%) had relapsed with first CR duration (CRD1) ≥12 months, and 11 (34.3%) had relapsed with CRD1 <12 months. After the first blinatumomab cycle, 22 (68.8%) achieved CR. At the end of the second cycle, 20 of the 22 patients remained in persistent CR, and 1 patient achieved new CR. The overall minimal residual disease negativity rate was 75% among evaluable patients with persistent CR. Patients with CRD1 <12 months were associated with poorer response to blinatumomab. Twenty (62.5%) of 32 patients underwent allo‐HCT in blinatumomab‐induced CR. After a median follow‐up of 15.2 months, the 1‐year OS rates for all patients and patients receiving allo‐HCT in CR were 55.5% (median OS, 18.2 months) and 70.7%, respectively. Patients with CRD1 <12 months, extramedullary disease (EMD), and high peripheral blood blasts were associated with poorer OS. Blinatumomab is effective for achieving good quality CR and bridging to allo‐HCT for adult patients with R/R Ph‐negative BCP‐ALL in first salvage. The role of blinatumomab in patients with CRD1 <12 months, EMD, or high tumor burden should be evaluated in future trials.