Tregzi, previously known as Orca-T during clinical development, is a personalized treatment manufactured from cells obtained from a matched donor. The product combines three key cellular components: hematopoietic stem and progenitor cells (HSPCs), highly purified regulatory T cells (Tregs), and conventional T cells. Together, these elements are designed to rebuild the patient’s blood and immune system, reduce the risk of GVHD, and preserve the beneficial graft-versus-leukemia effect that helps eliminate residual cancer cells.

Addressing a Long-Standing Transplant Challenge

Allogeneic stem cell transplantation remains a potentially curative option for patients with blood cancers such as acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), myelodysplastic syndrome (MDS), and mixed-phenotype acute leukemia (MPAL). However, the procedure is associated with significant complications, particularly chronic GVHD, infections, and treatment-related mortality.

Experts involved in the development and evaluation of Tregzi highlighted the therapy’s potential to improve outcomes by reducing transplant-related toxicities while maintaining anti-cancer activity. The approval also marks the first FDA authorization of a therapy built around highly purified regulatory T cells, reflecting years of research into the role of Tregs in controlling immune responses after transplantation.

Phase 3 Data Supported Approval

The FDA’s decision was based on findings from the randomized, multicenter Phase 3 Precision-T trial, which enrolled 187 patients aged 19 to 65 years, with a median age of 43.6 years. Participants had AML, ALL, high-risk MDS, or MPAL and were treated at 19 transplant centers across the United States.

The study compared Tregzi plus tacrolimus with conventional allogeneic HSCT using tacrolimus and methotrexate as GVHD prophylaxis.

At 12 months, patients receiving Tregzi demonstrated substantially improved outcomes:

• Chronic GVHD-free survival: 78% with Tregzi versus 38% with conventional transplantation.
• Chronic GVHD incidence: 13% compared with 44% in the control group.
• Overall survival: 94% versus 83%.
• GVHD-free and relapse-free survival: 63% versus 31%.
• Non-relapse mortality: 3% compared with 13%.

According to investigators, the improvement in chronic GVHD-free survival was largely driven by lower rates of chronic GVHD and fewer deaths.

Potential Impact on Patients

For individuals treated for blood cancers, long-term quality of life after transplantation can be significantly affected by chronic GVHD and other complications. Patient advocates welcomed the approval as a potential advance that could improve both recovery and long-term outcomes.

The clinical findings also indicated reductions in serious infections and treatment-related toxicity, factors that have historically contributed to morbidity and mortality following transplantation.

Precision-T Trial and Future Outlook

The Precision-T study (NCT05316701) was conducted as an open-label, randomized trial evaluating the safety, efficacy, and tolerability of Tregzi against standard allogeneic HSCT approaches. Results from the study were published in Blood in December 2025.

With the approval of Tregzi, Orca Bio advances its goal of developing high-precision cellular therapies for blood cancers and immune-mediated diseases. The company’s platform focuses on creating cell products with defined cellular compositions, aiming to replace diseased blood and immune systems while reducing the complications commonly associated with transplantation.

The approval represents a notable milestone in the evolution of cell therapy and transplant medicine, introducing a new approach that seeks to balance effective cancer control with a lower burden of transplant-related complications.