Hagop Kantarjian

Blinatumomab is a BiTE® (bispecific T‐cell engager) molecule that redirects CD3 + T‐cells to engage and lyse CD19 + target cells. Here we demonstrate that subcutaneous (SC) blinatumomab can provide high efficacy and greater convenience of administration. In the expansion phase of a multi‐institutional phase 1b trial (ClinicalTrials.gov, NCT04521231), heavily pretreated adults with relapsed/refractory B‐cell acute lymphoblastic leukemia (R/R B‐ALL) received SC blinatumomab at two doses: (1) 250 μg once daily (QD) for week 1 and 500 μg three times weekly (TIW) thereafter (250 μg/500 μg) or (2) 500 μg QD for week 1 and 1000 μg TIW thereafter (500 μg/1000 μg). The primary endpoint was complete remission/complete remission with partial hematologic recovery (CR/CRh) within two cycles. At the data cutoff of September 15, 2023, 29 patients were treated: 14 at the 250 μg/500 μg dose and 13 at 500 μg/1000 μg dose. Data from two ineligible patients were excluded. At the end of two cycles, 12 of 14 patients (85.7%) from the 250 μg/500 μg dose achieved CR/CRh of which nine patients (75.0%) were negative for measurable residual disease (MRD; <10 −4 leukemic blasts). At the 500 μg/1000 μg dose, 12 of 13 patients (92.3%) achieved CR/CRh; all 12 patients (100.0%) were MRD‐negative. No treatment‐related grade 4 cytokine release syndrome (CRS) or neurologic events (NEs) were reported. SC injections were well tolerated and all treatment‐related grade 3 CRS and NEs responded to standard‐of‐care management, interruption, or discontinuation. Treatment with SC blinatumomab resulted in high efficacy, with high MRD‐negativity rates and acceptable safety profile in heavily pretreated adults with R/R B‐ALL.