FDA Approves Tregzi: A New Way to Reduce Complications After Blood Cancer Transplants

In the Phase III Precision-T trial, 78% of Tregzi-treated patients were alive without moderate or severe chronic GVHD at one year, compared with 38.4% after standard transplant.

For adults facing high-risk blood cancers, a stem cell transplant can be a key treatment option with the potential for long-term disease control. However, these transplants carry a major risk called graft-versus-host disease (GVHD).

This serious complication occurs when donor immune cells mistake the patient’s body for a threat and attack healthy tissues, sometimes creating a long-term health burden after transplant.

Even with preventive measures, up to half of recipients develop GVHD. Chronic GVHD affects about 40% to 50% of allogeneic transplant recipients and can last for years or even a lifetime.

The FDA has approved Tregzi, a first-of-its-kind regulatory T cell-based immunotherapy designed to help adult patients survive their transplants without moderate or severe chronic GVHD.

Tregzi, also known clinically as Orca-T, is approved for adults with hematological malignancies, or blood cancers. It is used as part of a matched-donor transplant after high-intensity chemotherapy helps clear diseased cells and make room for donor cells. This is the first therapy to receive FDA approval from Orca Bio, a biotechnology company based in Menlo Park, California.

Blood cancers such as leukemia and myelodysplastic syndrome (MDS) often begin in the bone marrow, the factory where blood cells are produced. In a standard transplant, doctors replace a patient’s diseased blood-forming system with healthy cells from a donor. The challenge is that the same donor cells needed to attack remaining cancer can also trigger the immune response that leads to GVHD.

Tregzi takes a different approach by carefully controlling the types of cells a patient receives. It contains specialized stem cells to rebuild the blood system, regulatory T cells (Tregs) to help regulate immune activity and reduce GVHD risk, and conventional T cells to support immune recovery and help fight remaining cancer cells.

It is important to clarify that Tregzi is not a medicine added after a traditional transplant, but a precision-engineered donor-cell product used as part of the transplant itself. Tregzi is personalized for each patient.

The approval is based on the Phase III Precision-T trial, a study involving 187 adults with various blood cancers. The study included adults with acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome and mixed-phenotype acute leukemia.

Researchers compared patients who received Orca-T with those who underwent a traditional allogeneic stem cell transplant.

After one year, 78% of patients treated with Orca-T were alive and free of moderate or severe chronic GVHD, compared with 38.4% of patients who received a standard transplant. Serious chronic GVHD occurred in 12.6% of the Orca-T group, compared with 44% of the standard transplant group.

Additional data reported by Orca Bio showed that overall survival was 94% with Orca-T, compared with 83% for standard transplant. The rate of deaths not related to the cancer returning was also lower with Orca-T, at 3% compared with 13% for standard transplant.

This approval provides medical teams with a new way to rebuild a patient’s immune system while reducing the risk of one of the most serious long-term complications of transplantation. For patients, it offers the possibility of a smoother recovery while keeping the cancer-fighting benefits of a donor transplant intact.

Tregzi’s approval highlights growing clinical interest in Treg therapies. In January 2026, Cellenkos’ off-the-shelf Treg candidate, CK0804, received FDA Orphan Drug designation for myelofibrosis, with Phase II trials planned. Meanwhile, Quell Therapeutics has initiated a Phase I/II trial of QEL-005, a CAR-Treg candidate being studied in autoimmune diseases including rheumatoid arthritis and systemic sclerosis.

FAQs

Is Tregzi a gene therapy?

No. Tregzi is a cell therapy, not a gene therapy. Gene therapy usually works by adding, changing or replacing genes, while Tregzi uses living immune and stem cells from a matched donor.

How is Tregzi different from a standard stem cell transplant?

Tregzi controls the mix of donor cells a patient receives, including blood-forming stem cells, regulatory T cells and conventional T cells.

What did the Precision-T trial show?

After one year, 78% of Tregzi-treated patients were alive without moderate or severe chronic GVHD, compared with 38.4% of patients who received a standard transplant.

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