The U.S. Food and Drug Administration has approved Tregzi, the first regulatory T cell-based immunotherapy designed to improve chronic graft-versus-host disease-free survival in adults with blood cancers undergoing allogeneic hematopoietic stem cell transplantation.

The treatment, approved for certain adults with high-risk blood cancers, introduces a new approach to stem cell transplantation by helping the immune system rebuild while reducing the risk of chronic graft-versus-host disease, or GVHD, a serious complication in which transplanted donor blood cells attack the recipient's body, a news release from the from the agency said.

Patients receive Tregzi after chemotherapy prepares their bodies for a bone marrow or stem cell transplant.

"For patients with blood cancers who need stem cell transplantation, chronic graft-versus-host disease has long been one of the most feared and difficult-to-prevent complications," said Karim Mikhail, B.Pharm., M.S., acting director of the FDA's Center for Biologics Evaluation and Research, in the release. "Today's approval offers a genuine new approach that can help reconstitute the immune system while substantially reducing that risk and reflects the promise of what cellular therapy can deliver for patients."

Tregzi is a donor-derived cellular immunotherapy made up of three cell components: purified hematopoietic stem and progenitor cells, regulatory T cells and conventional T cells. The cells are collected from the blood of an 8/8 HLA-matched related or unrelated donor.

Regulatory T cells help control immune responses and maintain immune tolerance. The therapy is designed to lower the risk of chronic GVHD as the patient's blood-forming and immune systems recover following transplantation.

The FDA based its approval on results from the randomized PRECISION-T clinical trial, which enrolled 187 adults with blood cancers including acute leukemia and myelodysplastic syndrome. Participants were randomly assigned to receive either Tregzi or a standard stem cell transplant.

The trial measured chronic GVHD-free survival, defined as the time from transplantation until death from any cause or the first occurrence of moderate or severe chronic GVHD within two years.

At one year, 78% of patients treated with Tregzi achieved chronic GVHD-free survival compared with 38.4% of patients who received a standard transplant. After accounting for death as a competing risk, 12.6% of patients who received Tregzi developed serious chronic GVHD within one year compared with 44% of patients who underwent a standard transplant.

The FDA said the randomized controlled trial produced highly persuasive and internally consistent results demonstrating clinical benefit for the approved patient population and determined that the benefits of Tregzi outweigh its risks.

The most common side effects seen with Tregzi were infections, which the FDA said are generally consistent with those expected in patients undergoing stem cell transplantation. No patients experienced severe infusion reactions and no cases of graft failure were reported during the study period. The agency said patients and health care professionals should review the full prescribing information for complete safety information.

The application received Orphan Drug and Regenerative Medicine Advanced Therapy designations.

The FDA granted approval of Tregzi to Orca Biosystems Inc.