Blinatumomab In pediatric relapsed/refractory B-cell acute lymphoblastic leukemia: RIALTO expanded access study final analysis
The safety and efficacy of blinatumomab, a CD3/CD19-directed bispecific T-cell engager molecule, for treatment of pediatric relapsed/refractory B-cell precursor acute lymphoblastic leukemia (R/R B-ALL) were examined in an open-label, single-arm, expanded access study (RIALTO). Children (>28 days, <18 years) with CD19+ R/R B-ALL received up to five cycles of blinatumomab by continuous infusion (cycle: 4 weeks on/2 weeks off). The primary endpoint was incidence of adverse events. Secondary endpoints included complete response (CR) and measurable residual disease (MRD) response within the first two cycles, relapse-free survival (RFS), overall survival (OS) and allogeneic hematopoietic stem cell transplant (alloHSCT) after treatment. At final data cutoff (1/10/20), 110 patients were enrolled (median age, 8.5 years; 88% ≥5% blasts at baseline). Blinatumomab treatment resulted in a low incidence of grade 3-4 cytokine release syndrome (n=2 [1.8%]) and neurologic events (n=4 [3.6%]). No blinatumomab-related fatal adverse events were reported. The probability of response was not affected by the presence of cytogenetic/molecular abnormalities. Median OS was 14.6 months (95%CI: 11.0─not estimable) and was significantly greater for MRD responders versus MRD non-responders (not estimable vs 9.3; HR 0.18, 95%CI: 0.08─0.39). One-year OS probability was higher for patients who received alloHSCT versus without alloHSCT post-blinatumomab (87% versus 29%). Median RFS for MRD responders (n=57) was 8.0 months (95%CI:3.4─10.1) versus 2.8 months (95%CI: 0.3─9.2) for MRD non-responders (n=10). Of patients achieving CR after 2 cycles, 73.5% (95%CI: 61.4%-83.5%) proceeded to alloHSCT. These findings support the use of blinatumomab as a safe and efficacious treatment for pediatric R/R B-ALL. (ClinicalTrials.gov identifier NCT02187354)