Safety of allogeneic hematopoietic cell transplant in adults after CD19-targeted CAR T-cell therapy.

Allogeneic hematopoietic cell transplantation (allo-HCT) is offered to selected patients after chimeric antigen receptor-modified T-cell (CAR-T) therapy. Lymphodepleting chemotherapy and CAR-T therapy have immunosuppressive and immunomodulatory effects that could alter the safety profile of subsequent allo-HCT. We reviewed our experience with 32 adults (acute lymphoblastic leukemia [ALL], n = 19; B-cell non-Hodgkin lymphoma [NHL]/chronic lymphocytic leukemia [CLL], n = 13) who received an allo-HCT after CAR-T therapy, with a focus on posttransplant toxicities. Myeloablative conditioning (MAC) was used in 74% of ALL patients and 39% of NHL/CLL patients. The median time from CAR-T therapy to allo-HCT was 72 days in ALL patients and 122 days in NHL/CLL patients. Cumulative incidences of grade 3-4 acute graft-versus-host disease (GVHD) and chronic GVHD were 25% and 10%, respectively. All patients had neutrophil recovery (median, 18.5 days) and all but 3 had platelet recovery (median, 12 days). Twenty-two percent had viral or systemic fungal infection within 100 days after allo-HCT. The 100-day and 1-year cumulative incidences of NRM were 16% and 21%, respectively, for ALL patients and 15% and 33%, respectively, for NHL/CLL patients. In ALL patients, later utilization of allo-HCT after CAR-T therapy was associated with higher mortality. In NHL/CLL patients, MAC was associated with higher mortality. Toxicities did not exceed the expected incidences in this high-risk population.