Matched donor allogeneic CAR-T for adult B-ALL: toxicity, efficacy, repeat dosing, and the importance of lymphodepletion

ABSTRACT: We developed an allogeneic matched donor CD19 chimeric antigen receptor (CAR) product (CAR-donor lymphocyte infusion [DLI]) for adult patients with B-cell acute lymphoblastic leukemia (B-ALL) after failure of allogeneic stem-cell transplantation (allo-SCT). We evaluate the risks and benefits of pre-CAR-DLI lymphodepleting chemotherapy (LD) and the efficacy of repeat CAR-DLI dosing per conventional DLI protocols. Primary outcomes were toxicity and feasibility of CAR-DLI manufacture; secondary outcomes included CAR-DLI engraftment, expansion, and persistence. A total of 17 allo-SCT donors received leukapheresis and 14 patients with B-ALL (median age, 43 years) received infusion. Median disease burden at registration was 50.5% bone marrow blasts (range, measurable residual disease [MRD] to 100%). Patients 1 to 7 received CAR-DLI alone (CAR-DLI-alone); patients 8 through 14 received CAR-DLI and LD with fludarabine/cyclophosphamide (CAR-DLI+LD). CAR-DLI+LD vs CAR-DLI-alone was associated with superior peak CAR-DLI engraftment (93 134 vs 8010 copies per μg genomic DNA [gDNA]), expansion (858 101 vs 39 038 copies per μg gDNA per 28 days) and persistence (median, 197 vs 32 days). CAR-DLI+LD was not associated with more immunotoxicity than CAR-DLI-alone, and graft-versus-host disease (GVHD; grade 1, skin) affected only 2 of 14 patients (14%). CAR-DLI+LD vs CAR-DLI-alone conferred superior event-free-survival and overall survival at 12 months (57% vs 29%; 83% vs 29%). Repeat CAR-DLI dosing was administered to 8 of 14 (57%) patients with morphological/MRD+ relapse, but with minimal engraftment/expansion or toxicity/efficacy. CAR-DLI+LD has a tolerable safety profile without significant GVHD and is associated with significantly better outcomes than CAR-DLI-alone. Repeat CAR-DLI dosing beyond dose 1 was not found to be effective in this analysis. This trial was registered at www.clinicaltrials.gov as #NCT02893189.