FDA Grants First-in-Class Approval for Treg Cell Therapy in Blood Cancer Transplant Patients

The FDA announced on June 30, 2026 that it has approved Tregzi for the treatment of chronic graft-versus-host disease (GVHD), a condition in which transplanted donor blood cells attack the recipient's body.1 Tregzi, a donor-derived cellular immunotherapy developed by Orca Biosystems, is the first regulatory T-cell-based immunotherapy approved for improving chronic GVHD-free survival in this patient population, marking a shift in how transplant centers might approach an outcome that has historically been difficult to prevent through pharmacologic means alone.

"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 Center for Biologics Evaluation and Research, in a press release.1 "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."

“For transplant physicians, one of our greatest challenges has long been preserving the vital graft-versus-leukemia effect while minimizing the risk of GVHD and infection,” said Miguel-Angel Perales, M.D., medical oncologist and chief of the Adult Bone Marrow Transplant Service at Memorial Sloan Kettering Cancer Center, in a press release.2 “The FDA approval of TREGZI signals a new era in transplant medicine. This precision-engineered cell therapy is built on the foundational principles established by our early CD34 cell selection work and can now be delivered at scale, equipping providers with a new option to reduce serious toxicities and improve treatment outcomes."

How the Cell Therapy Is Manufactured and Administered

Unlike a standard stem cell transplant, which typically infuses a single population of donor cells, Tregzi is composed of 3 distinct cell components manufactured from a single donor collection: purified hematopoietic stem and progenitor cells, regulatory T cells, and conventional T cells. All 3 are derived from the mobilized peripheral blood of a donor who is an 8/8 human leukocyte antigen match, either a relative or an unrelated donor.

Regulatory T cells are immune cells that help regulate immune responses and maintain immune tolerance. By isolating and formulating this cell type alongside the stem and progenitor cells and conventional T cells, the therapy is intended to support reconstitution of a patient's blood-forming and immune systems while lowering the likelihood that donor-derived cells will attack healthy tissue. Patients receive the treatment after a course of chemotherapy that prepares the body for the transplant.

"We founded Orca Bio on the audacious goal to engineer living cells into curative medicines, rooted in the belief that single-cell precision could fundamentally rewrite patient outcomes," said Nate Fernhoff, PhD, co-founder and chief executive officer of Orca Bio, in a press release.2 "The FDA approval of TREGZI is a significant milestone that stands on the shoulders of decades of pioneering science. As we enter this next chapter, our focus turns to the immense responsibility of delivering TREGZI reliably, precisely and safely to the patients and families counting on us."

Trial Data Behind the Chronic GVHD-Free Survival Endpoint

The approval was based on findings from PRECISION-T, a randomized controlled trial that enrolled 187 adult patients with blood cancers, including acute leukemia and myelodysplastic syndrome. Participants were assigned to receive either Tregzi or a standard stem cell transplant, and the trial's primary endpoint was chronic GVHD-free survival. This was measured as the time from transplantation to the earliest occurrence of either death from any cause or the first onset of moderate or severe chronic GVHD, tracked within 2 years of the transplant date.

After 1 year, 78% of patients who received Tregzi met this endpoint, compared with 38.4% of those who received a standard transplant. When death was accounted for as a competing risk, 12.6% of Tregzi recipients developed serious chronic GVHD within a year, versus 44% among patients who received a standard transplant. According to FDA, the trial's results demonstrate clinical benefit for the studied population; therefore, the agency concluded that Tregzi's benefits outweigh its risks.

The safety profile observed in the trial was consistent with patients undergoing stem cell transplantation, with infection as the most common adverse event. No severe reactions occurred during infusion, and no cases of graft failure were reported during the study period.

“Developing this concept from early foundational research in our labs based upon the fundamental biology of regulatory T cells, to it now receiving the first FDA approval for a therapy that utilizes highly purified Tregs, is a defining moment for the transplant community," said Robert Negrin, M.D., professor of medicine, blood and marrow transplantation at Stanford Medicine, in a press release.2 "The peer-reviewed findings demonstrated this precision-engineered cell therapy delivered improved GVHD-free survival alongside less toxicity, including fewer serious infections and lower non-relapse mortality."

The application received both Orphan Drug and Regenerative Medicine Advanced Therapy designations ahead of its approval.

References

1. FDA approves new treatment that uses donor immune cells to prevent serious complications in blood cancer patients. Press release. FDA. June 30, 2026. https://www.fda.gov/news-events/press-announcements/fda-approves-new-treatment-uses-donor-immune-cells-prevent-serious-complications-blood-cancer
2. Orca Bio’s TREGZI™ receives U.S. FDA approval as first and only precision-engineered cell therapy for allogeneic transplant in adults with hematological malignancies. Press release. Orca Bio. June 30, 2026. https://orcabio.com/orca-bios-tregzi-receives-u-s-fda-approval-as-first-and-only-precision-engineered-cell-therapy-for-allogeneic-transplant-in-adults-with-hematological-malignanciesorca-bio-adds-east/