The FDA approved Tregzi (Orca-T) on June 30, clearing Orca Bio’s engineered cell therapy for adults with hematological malignancies undergoing allogeneic hematopoietic stem cell transplantation. The approval makes Tregzi the first regulatory T-cell-enriched donor cell product authorized specifically to reduce the incidence and severity of chronic graft-versus-host disease, a complication that remains one of the leading causes of long-term morbidity in transplant survivors.

Chronic GVHD occurs when donor immune cells attack the recipient’s healthy tissue after a transplant intended to treat blood cancers such as acute myeloid leukemia or myelodysplastic syndrome. Despite decades of progress in transplant conditioning and supportive care, chronic GVHD still develops in a substantial share of patients who receive standard donor grafts, often requiring long courses of immunosuppression that raise the risk of infection and relapse. Orca Bio’s approach involves processing the donor graft to enrich it with regulatory T cells, a subset of immune cells that suppress excessive immune activation, while depleting the conventional T cells most responsible for triggering graft-versus-host attacks.

The pivotal data supporting approval came from a randomized trial comparing Orca-T to standard-of-care unmanipulated grafts in patients receiving matched donor transplants. Patients who received the engineered graft showed a significantly lower rate of moderate to severe chronic GVHD at one year post-transplant, alongside comparable rates of relapse and overall survival relative to the control arm, addressing a key concern that suppressing graft-versus-host activity might also blunt the beneficial graft-versus-leukemia effect that helps prevent cancer recurrence.

Manufacturing represents both the innovation and the operational challenge at the center of Tregzi’s rollout. Because the product must be processed from a specific donor’s cells and delivered within a defined window around the transplant, Orca Bio has built a centralized processing model in which fresh graft material is shipped to the company’s facility for cell separation and enrichment before being returned to the transplant center. The company said it is prioritizing onboarding of transplant centers with high allogeneic transplant volumes as it scales commercial supply through the remainder of 2026.

Chronic GVHD management has historically relied on steroids and, more recently, targeted agents such as ruxolitinib and belumosudil for patients who fail first-line therapy. Tregzi’s approval shifts the intervention point upstream, aiming to prevent the complication at the time of transplant rather than treating it after it emerges. Hematologists who worked on the trial said this preventive framing, rather than a new treatment for established disease, is what differentiates the product from the current GVHD armamentarium.

Orca Bio will need to demonstrate durable real-world outcomes as adoption widens beyond the controlled trial setting, and payers will be watching the cost of a bespoke, per-donor manufacturing process closely relative to standard transplant costs. Still, the approval gives transplant physicians a new tool aimed squarely at one of the field’s most persistent unmet needs.