FDA Approves Orca Bio's Tregzi, the First Regulatory T-Cell Therapy, to Cut Chronic GVHD After Stem-Cell Transplant in Blood Cancer

Overview

The U.S. Food and Drug Administration has approved Tregzi, developed by Orca Bio, as the first approved cell therapy using regulatory T cells, for adults with blood cancers undergoing an allogeneic stem-cell transplant, BioSpace reported. The approval was announced on July 1, 2026, according to Orca Bio.

Chronic graft-versus-host disease is one of the most feared complications of a stem-cell transplant: the donor’s transplanted immune cells attack the recipient’s healthy tissue. Tregzi aims to blunt that reaction by delivering regulatory T cells — the immune system’s own brake — as part of a precision-engineered graft.

What We Know

Orca Bio said Tregzi was approved “for use in matched donor hematopoietic stem cell transplantation with myeloablative preparative regimen, for hematopoietic and immunologic reconstitution and to improve chronic graft-versus-host-free survival, in the treatment of adults with hematological malignancies,” in its announcement. The therapy, known clinically as Orca-T, is used in patients undergoing transplant for cancers including acute myeloid leukemia, acute lymphoblastic leukemia, myelodysplastic syndrome, and mixed-phenotype acute leukemia, BioSpace reported.

Approval rested on Precision-T, a randomized, open-label, multicenter phase 3 study of 187 patients with a primary endpoint of chronic GVHD-free survival at 12 months, Orca Bio said. Patients were randomly assigned to receive either Tregzi plus single-agent tacrolimus or conventional allogeneic hematopoietic stem cell transplant plus tacrolimus and methotrexate, according to BioSpace.

At 12 months, chronic GVHD-free survival was 78% in the Tregzi arm versus 38% for conventional transplant; the rate of chronic GVHD was 13% versus 44%; overall survival was 94% versus 83%; and non-relapse mortality was 3% versus 13%, per Orca Bio.

On safety, Orca Bio reported that the most common adverse reactions occurring in at least 20% of patients were “Mucositis, diarrhea, rash, viral infections, abdominal pain, vomiting, nausea, bacterial infections, hemorrhage, acute GVHD, edema, fungal infections,” in its announcement.

Karim Mikhail, acting director of the FDA’s Center for Biologics Evaluation and Research, framed the decision’s significance, BioSpace reported. Orca Bio chief executive Nate Fernhoff said the approval “marks a defining moment for Orca Bio and for the future of allogeneic transplant,” according to BioSpace.

What We Don’t Know

The efficacy figures reported at approval reflect the 12-month timepoint, and longer-term chronic-GVHD-free survival data were not detailed in the coverage reviewed. Fernhoff, speaking to STAT, cast the decision as an attempt to change the calculus of transplantation itself. “Historically, the choice for a stem cell transplant carried a trade-off — risks and complications that patients had to accept as part of treatment in search of a cure. With Tregzi’s approval, we hope to show that we can break that trade-off, and that we can improve survival free from graft-versus-host disease,” he told STAT. How the therapy performs outside the matched-donor, myeloablative population covered by the label — and how broadly transplant centers can manufacture and deliver a precision-engineered graft — remains to be established.

Analysis

Tregzi’s approval marks the first time the FDA has cleared a therapy built on regulatory T cells, BioSpace reported, extending engineered cell products from treating cancer directly, as CAR-T does, to reshaping the immune consequences of transplantation. The Precision-T results point to a break in the field’s long-standing trade-off between suppressing GVHD and preserving the graft’s benefit: the Tregzi arm posted both higher GVHD-free survival and lower non-relapse mortality than conventional transplant, according to Orca Bio. Whether that balance holds across the wider transplant population, and whether the logistics of delivering an engineered graft scale beyond specialized centers, will shape how quickly the approach spreads.