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.