Outcomes of blinatumomab based therapy in children with relapsed, persistent, or refractory acute lymphoblastic leukemia: a multicenter study focusing on predictors of response and post-treatment immunoglobulin production.The management of Refractory/Relapsed B-cell Acute Lymphoblastic Leukemia (R/R ALL) remains challenging.  Incorporating blinatumomab in R/R ALL treatment has shown encouraging results.  We describe the outcome and predictors of response in children receiving blinatumomab as a bridge to definitive therapy.  Thirty-three patients that failed standard first-line treatments due to relapsed ALL (n = 22), persistent minimal residual disease (MRD) (n = 8), or refractory disease (n = 3) received blinatumomab.  Grade 2 toxicity occurred in 27.2% of patients.  MRD remission (<0.01%) was achieved in 72.7% of patients.  Pre-blinatumomab absolute lymphocyte count (ALC) and MRD/ALC ratio significantly associated with MRD-response.  Patients with t(1;19) translocation had lower response rate, compared to all other cytogenetic categories (p = 0.013).  One-year event-free survival (EFS) and overall survival (OS) were 69.2% and 79.7%, respectively.  Analysis of OS and EFS showed pre-blinatumomab MRD level, ALC, MRD/ALC ratio, t(1;19), and post-blinatumomab MRD remission associated with survival.  IgG seronegative status was observed in 83% (12/15) for varicella zoster, 35% (6/17) for herpes zoster, 18% (3/17) for cytomegalovirus, and 26% (5/17) for Epstein Barr virus.  Blinatumomab produced encouraging results in children with R/R ALL and low disease burden bridging to definitive therapy.  Incorporating baseline genetics and biomarkers may help identify subgroups likely to be responsive/resistant to therapy.  Viral serological testing pre- and post-blinatumomab is recommended to optimize supportive and preemptive therapy.Supplemental data for this article is available online at https://doi.org/10.1080/08880018.2022.2049936 .
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