Orca-T vs allogeneic hematopoietic stem cell transplantation (Precision-T): a multicenter, randomized phase 3 trial.

To prevent graft-versus-host disease (GVHD) in patients undergoing myeloablative allogeneic hematopoietic stem cell transplantation (alloHSCT), a calcineurin inhibitor plus methotrexate is routinely used. Early phase studies suggested improved outcomes with Orca-T, an allogeneic T-cell immunotherapy that uses purified donor regulatory T cells to prevent GVHD with significantly less immunosuppression. This phase 3 trial randomized adult patients (N = 187) with acute leukemias or myelodysplastic syndrome undergoing myeloablative conditioning to receive either Orca-T with tacrolimus or a conventional allograft with tacrolimus and methotrexate (Tac/MTX), using granulocyte colony-stimulating factor-mobilized peripheral blood from HLA-matched donors. The primary end point was survival free from moderate-to-severe chronic GVHD (cGVHD; cGFS). Using a stratified log-rank test, cGFS was significantly higher in the Orca-T arm than in Tac/MTX (hazard ratio, 0.26; 95% confidence interval, 0.14-0.47; P< .001). One-year estimates were as follows: cGFS was 78.0% with Orca-T vs 38.4% with Tac/MTX; cumulative incidence of moderate-to-severe cGVHD was 12.6% with Orca-T and 44.0% with Tac/MTX (Gray test P< .001); overall survival was 93.9% with Orca-T vs 83.1% with Tac/MTX (P = .12); GVHD-free and relapse-free survival was 63.1% and 30.9% in the Orca-T and Tac/MTX arms (P< .001), respectively; nonrelapse mortality (NRM) was 3.4% with Orca-T vs 13.2% with Tac/MTX (P = .03). Orca-T met the primary end point of improved survival free from cGVHD compared with Tac/MTX prophylaxis and should be considered a new therapeutic option with low toxicity for GVHD prophylaxis. Moreover, significantly less toxicity was observed with Orca-T patients, including fewer serious infectious complications and less NRM. This trial was registered at www.clinicaltrials.gov as NCT05316701.