SILVER SPRING, Maryland, June 30, 2026
The U.S. Food and Drug Administration (FDA) has approved Tregzi, developed by Orca Biosystems, as the first regulatory T-cell (Treg)-based immunotherapy designed to improve chronic graft-versus-host disease (GVHD)-free survival in adult patients with high-risk blood cancers undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). The landmark approval introduces an innovative donor-derived cellular immunotherapy that not only supports immune system recovery following stem cell transplantation but also significantly reduces the risk of chronic GVHD, one of the most severe and life-threatening complications associated with bone marrow transplantation. By utilizing regulatory T cells (Tregs) alongside hematopoietic stem and progenitor cells (HSPCs) and conventional T cells (Tcons) collected from an 8/8 HLA-matched donor, Tregzi represents a major advancement in cell therapy, offering a new therapeutic strategy that balances cancer control with long-term immune tolerance. The approval also highlights continued progress in regenerative medicine and advanced cellular immunotherapies for hematologic malignancies.
First Regulatory T-Cell Therapy Reduces Chronic GVHD Risk
Tregzi is the first FDA-approved therapy built on regulatory T-cell (Treg) technology, a specialized population of immune cells responsible for maintaining immune tolerance and controlling excessive immune responses. During allogeneic stem cell transplantation, donor immune cells can mistakenly attack healthy tissues in the recipient, resulting in chronic graft-versus-host disease, a serious condition affecting multiple organs and significantly impacting long-term survival and quality of life. Tregzi is specifically designed to restore immune balance during the rebuilding of the patient’s blood-forming and immune systems following chemotherapy and transplantation.
The therapy combines purified hematopoietic stem cells, regulatory T cells, and conventional T cells, all derived from closely matched donor peripheral blood, to enhance immune reconstitution while minimizing harmful immune reactions. This novel cellular approach addresses one of the most significant unmet needs in hematopoietic stem cell transplantation by improving both transplant success and long-term patient outcomes.
Clinical Trial Demonstrates Significant Survival Benefit
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The FDA approval was supported by results from the Phase III PRECISION-T clinical trial, which enrolled 187 adult patients with acute leukemia, myelodysplastic syndrome, and other high-risk blood cancers requiring allogeneic stem cell transplantation. Participants were randomly assigned to receive either Tregzi or a conventional stem cell transplant. The study’s primary endpoint evaluated chronic GVHD-free survival within two years after transplantation. Results demonstrated a substantial clinical advantage for patients receiving Tregzi, with 78% achieving chronic GVHD-free survival at one year, compared with 38.4% among patients receiving standard transplantation. Furthermore, only 12.6% of patients treated with Tregzi developed moderate or severe chronic GVHD during the first year, compared with 44% in the control group.
The therapy also demonstrated a favorable safety profile, with adverse events generally consistent with those expected following stem cell transplantation. Importantly, investigators reported no severe infusion-related reactions and no cases of graft failure, reinforcing confidence in the therapy’s clinical safety and effectiveness.
FDA Approval Advances Cellular Immunotherapy Innovation
The approval of Tregzi represents a significant milestone in the evolution of cellular immunotherapy and regenerative medicine, expanding treatment options for patients with life-threatening hematologic malignancies who require stem cell transplantation. The therapy previously received both Orphan Drug Designation and Regenerative Medicine Advanced Therapy (RMAT) Designation, recognizing its potential to address a serious unmet medical need. By introducing regulatory T-cell therapy into routine clinical practice, Orca Biosystems has established a new paradigm for preventing transplant-related immune complications while preserving the beneficial anti-cancer effects of donor immune cells.
As advances in cell therapy, immune engineering, and personalized transplantation continue to reshape oncology care, Tregzi has the potential to significantly improve long-term survival, reduce treatment-related complications, and enhance quality of life for patients undergoing stem cell transplantation. The FDA’s approval marks an important step toward broader adoption of precision cellular therapies capable of transforming outcomes across hematology and regenerative medicine.
Source: FDA press release
