FDA Grants RMAT Designation to Orca-Q for High-Risk Blood Cancers

The FDA granted regenerative medicine advanced therapy (RMAT) designation to Orca-Q, a second-generation investigational allogeneic T-cell immunotherapy for the treatment of high-risk hematologic malignancies, according to a news release from Orca Bio.¹

The designation was based on promising preliminary clinical data from an ongoing phase 1 study (NCT03802695) demonstrating durable and encouraging outcomes across key efficacy and safety metrics, including overall survival, acute and chronic graft-vs-host disease (GVHD), and nonrelapse mortality. New clinical findings and longer follow-up data are expected later in 2026.

RMAT Designation and Its Significance

RMAT designation is a specialized FDA program created to accelerate the development and review of promising regenerative medicine therapies, including cell and gene therapies, intended to treat serious or life-threatening conditions. To qualify, a therapy must demonstrate preliminary clinical evidence suggesting the potential to address unmet medical needs. The designation provides increased FDA guidance throughout development, as well as eligibility for priority review, rolling review, and accelerated approval pathways. This marks the company’s second cell therapy candidate to receive RMAT status, the first being Orca-T.

Phase 1 Clinical Data Supporting the Designation

The RMAT application was supported by data from the ongoing phase 1 trial evaluating Orca-Q across 6 treatment cohorts in patients with hematologic malignancies. Interim results presented at the 52nd Annual Meeting of the European Blood and Marrow Transplantation Society in Madrid, Spain included preliminary safety and efficacy findings from the haploidentical donor cohort.²

Outcomes were reported for 39 evaluable patients under age 65 with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), or myelodysplastic syndromes (MDS), with a median follow-up of 937 days (range, 19-1825 days) and a median age of 44 years (range, 21-64). All patients received myeloablative conditioning (MAC) with 1 of 3 busulfan- or total body irradiation–based regimens prior to haploidentical transplantation with Orca-Q.

Overall survival (OS) rates at 1, 2, and 3 years were 80%, 77%, and 77%, respectively, across all patients. Relapse-free survival (RFS) at 1 year was 77%, and GVHD-free, relapse-free survival (GRFS), a composite end point capturing the first occurrence of Grade 3 to 4 acute GVHD, moderate-to-severe chronic GVHD, relapse, or death, was 72% at 1 year. Nonrelapse mortality at 1 year was 5.8%, and the cumulative incidence of relapse at 1 year was 18.2%. Grade 3 to 4 acute GVHD at day 180 occurred in 8.1% of patients, and moderate-to-severe chronic GVHD at 1 year was 0%. Bloodstream and other serious infections (BMT CTN grade 3+) at 1 year occurred in 5.3% of patients.

Outcomes in the TBI/Flu/Thio Conditioning Subgroup

Outcomes were notably more favorable in the subgroup of 14 patients receiving total body irradiation, fludarabine, and thiotepa (TBI/Flu/Thio) conditioning, with a median follow-up of 1244 days. OS at 1, 2, and 3 years was 85%, 85%, and 85% in this subgroup, with 1-year RFS of 85% and 1-year GRFS of 85%. Nonrelapse mortality at 1 year was 7.7%, relapse incidence was 8.4%, and grade 3 or 4 acute GVHD at day 180 was 0% in this subgroup. Mean cumulative serious adverse events at 1 year were 0.43 in the TBI/Flu/Thio subgroup vs 1.08 for patients on other conditioning regimens, suggesting a meaningfully better tolerability profile with this preparative regimen.

Manufacturing Feasibility and Engraftment

Orca-Q was successfully manufactured and administered for all 39 patients, with a vein-to-vein time of less than 72 hours for 100% of products, a clinically important logistical achievement for a precision-engineered cellular therapy. All patients achieved neutrophil engraftment by day +19, with a median engraftment time of 11 days. Two patients who received busulfan-based conditioning experienced secondary graft failure.

Orca-Q: Mechanism and Platform

Orca-Q is a proprietary composition of stem cells combined with specific T-cell subsets derived from healthy donors and engineered using Orca Bio’s high-precision manufacturing platform. The platform uses single-cell precision technology to create uniquely defined cellular products with a controlled composition, designed to replace a patient’s diseased blood and immune system with a healthy one from a matched or partially matched donor. By selectively enriching specific T-cell subsets and controlling the cellular composition at the single-cell level, Orca-Q aims to preserve the graft vs leukemia effect while reducing the alloreactive T-cell activity responsible for GVHD, a balance that has historically been difficult to achieve with conventional transplant approaches.

Expanded Trial and Unmet Need

The phase 1 trial has recently been expanded to include additional cohorts of patients receiving reduced intensity or nonmyeloablative conditioning with matched, 7/8 mismatched, or haploidentical donors, extending potential eligibility to older or less fit patients who cannot tolerate myeloablative preparative regimens. Haploidentical transplantation is particularly important for patients who lack a fully matched donor, a barrier that has historically excluded a substantial proportion of patients from transplant eligibility. High-risk hematologic malignancies carry poor prognoses with standard therapies, and allogeneic hematopoietic cell transplantation remains the only potentially curative option for many patients; however, transplant-related complications, particularly GVHD and nonrelapse mortality, limit its benefit.

The company plans to present more detailed data from the trial with longer follow-up at upcoming scientific meetings in 2026.

“With our newly expanded phase 1 study continuing to enroll patients and additional data expected later this year, we remain focused on advancing our high-precision approach to deliver an important new treatment to patients with blood cancer,” Nate Fernhoff, PhD, co-founder and chief executive officer at Orca Bio, stated in the news release.

REFERENCES

1. Orca Bio Announces U.S. FDA Regenerative Medicine Advanced Therapy (RMAT) Designation Granted to Orca-Q for the Treatment of High-Risk Hematologic Malignancies. News release. Orca Bio. April 28, 2026. Accessed May 1, 2026. https://tinyurl.com/sxfe76nb

2. Salhotra A, Srour SA, Abedi M, et al. Preliminary safety and efficacy of myeloablative Orca-Q in patients with haploidentical donors. Presented at: 2026 EBMT Annual Meeting; March 22-25, 2026; Madrid, Spain. A043.