The United States Food and Drug Administration (FDA) approved Tregzi on Wednesday, July 1, 2026 — marking the first-ever regulatory T (Treg) cell–based immunotherapy cleared to improve chronic graft-versus-host disease (GVHD)–free survival in adult blood cancer patients undergoing donor stem cell transplants.
The approval was granted to California-based Orca Biosystems, Inc., and addresses one of transplantation medicine's most persistent and feared complications: donor cells attacking the recipient's own body even after a successful transplant clears the original cancer.
What Chronic GVHD Means for Blood Cancer Patients
Allogeneic hematopoietic stem cell transplants — procedures using blood-forming cells from a closely matched donor — remain among the most effective treatments for blood cancers such as acute leukemia and myelodysplastic syndrome. However, even a successful transplant can leave patients vulnerable to chronic GVHD, a serious condition in which the transplanted immune cells recognize the recipient's body as foreign and launch an attack against it.
Chronic GVHD can significantly diminish quality of life and survival prospects, and has historically been difficult to prevent with standard transplant protocols.
How Tregzi Works
Tregzi is administered following chemotherapy that prepares a patient's body to receive the transplant. It is built from three distinct cell types drawn from the donor's blood: purified blood-forming stem and progenitor cells, Treg cells, and conventional T cells. All cells are sourced from an 8/8 HLA-matched related or unrelated donor — meaning the donor and recipient share closely matched immune-system markers across eight key genetic points.
Treg cells play a central role in regulating immune responses and maintaining immune tolerance. By incorporating these cells into the transplant preparation, Tregzi aims to allow the patient's blood and immune systems to rebuild while reducing the likelihood that donor cells will attack the recipient's body.
PRECISION-T Trial Results Drive Approval
The FDA's approval rests on data from the PRECISION-T trial, a randomized study of 187 adults diagnosed with blood cancers including acute leukemia and myelodysplastic syndrome. Participants were assigned to receive either Tregzi or a standard stem cell transplant, according to the FDA.
The primary endpoint was chronic GVHD–free survival — defined as the time from transplant until either death from any cause or the first onset of moderate or severe chronic GVHD within two years.
At the one-year mark, 78 percent of patients in the Tregzi group met that outcome, compared with 38.4 percent of those who received a standard transplant. Accounting for death as a competing risk, 12.6 percent of Tregzi patients developed serious chronic GVHD within one year, against 44 percent in the standard-transplant group.
The FDA concluded that the benefits of Tregzi outweigh its risks.
Safety Profile and Known Side Effects
Reported side effects were generally consistent with what is expected during stem cell transplantation, with infections being the most commonly observed adverse event, according to FDA prescribing information.
Notably, no patient experienced a severe reaction during the Tregzi infusion, and no cases of graft failure — a serious complication in which the transplanted cells fail to take hold — were recorded during the study period. The FDA and Orca Biosystems advise patients and clinicians to review the full prescribing information for complete safety and dosing details.
FDA Acting Director Cites Significance of Approval
"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. 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."
— Karim Mikhail, Acting Director, FDA Center for Biologics Evaluation and Research
Special Designations Granted to Tregzi
The FDA granted Tregzi both Orphan Drug designation and Regenerative Medicine Advanced Therapy (RMAT) designation during its development. Orphan Drug designation is awarded to therapies targeting rare diseases and provides certain regulatory incentives to encourage development. RMAT designation is reserved for cell and gene therapies that show early clinical evidence of addressing serious conditions, according to the FDA.
These designations reflect the FDA's recognition that blood cancer patients undergoing stem cell transplants represent a medically underserved population with significant unmet needs in preventing transplant-related complications.
By the Numbers
- 187 — adult blood cancer patients enrolled in the PRECISION-T randomized trial
- 78% — Tregzi patients who achieved chronic GVHD–free survival at one year
- 38.4% — standard-transplant patients who achieved GVHD–free survival at one year
- 12.6% — Tregzi patients who developed serious chronic GVHD within one year
- 44% — standard-transplant patients who developed serious chronic GVHD within one year
- 8/8 — HLA match points required between donor and recipient for Tregzi eligibility
- 2 — special FDA designations granted: Orphan Drug and Regenerative Medicine Advanced Therapy
Why This Matters
Tregzi's approval represents the first time a Treg cell–based therapy has been cleared by a major regulatory authority to reduce one of the most serious and persistent complications of blood cancer transplantation. The PRECISION-T trial showed that Tregzi more than doubled the rate of chronic GVHD–free survival at one year compared with standard transplants — from 38.4 percent to 78 percent — while cutting the incidence of serious GVHD from 44 percent to 12.6 percent. For adult patients with acute leukemia, myelodysplastic syndrome, and other blood cancers who have limited treatment options after transplant, the availability of this therapy marks a meaningful clinical advance.
Photo credit: Photo from FDA.gov