RGI-2001 for the prophylaxis of acute graft-versus-host disease after allogeneic HCT.

RGI-2001, a glycolipid that binds CD1d receptor of antigen-presenting cells, can activate invariant natural killer T (NKT) cells and stimulate cytokine-dependent proliferation of regulatory T cells (Tregs). This open-label, multicenter phase 2b trial evaluated the safety and efficacy of RGI-2001 in combination with standard graft-versus-host disease (GVHD) prophylaxis in participants receiving myeloablative allogeneic hematopoietic cell transplantation (HCT). RGI-2001 was infused at a dose of 100 μg/kg for 6 weekly doses. The primary end point was grade 2 to 4 acute GVHD by day 100. A total of 49 participants received RGI-2001 in combination with tacrolimus and methotrexate. RGI-2001 was well tolerated, with no serious infusion reactions. Sixteen participants experienced grade ≥3 treatment-related adverse events, including decreased appetite, leukopenia, thrombocytopenia, and stomatitis. The cumulative incidence of grade 2 to 4 and 3 to 4 acute GVHD were 24.9% and 4.1%, respectively. Compared with the controls from the Center for International Blood and Marrow Research Transplant registry, participants receiving RGI-2001 experienced superior clinical outcomes, including day-180 grade 2 to 4 acute GVHD-free survival (70.8% vs 50.7%; adjusted hazard ratio, 0.45; 95% confidence interval, 0.30-0.68). Increasing NKT and Treg populations were observed after HCT, consistent with the proposed action of RGI-2001. In conclusion, RGI-2001 was well tolerated and was associated with low rates of acute GVHD and encouraging survival after myeloablative HCT. These results support strategies that target NKT and Treg cell populations to augment immunologic changes in allogeneic HCT recipients. This trial was registered at www.clinicaltrials.gov as #NCT04014790.