A novel T-cell engineered product, Orca-T (Orca Bio), was associated with lower incidence of both acute and chronic graft-versus-host disease (GVHD) and more than double the rate of GVHD-free and relapse-free survival, compared with the current standard of care for patients undergoing hematopoietic stem cell transplants (HSCT), investigators said.
In both a multicenter phase 1 trial (NCT04013685) and single-center phase 1/2 trial (NCT01660607) with a total of 50 patients, those who received Orca-T with single-agent GVHD prophylaxis had a 1-year GVHD-free and relapse-free survival rate of 75%, compared with 31% for patients who received standard of care with two-agent prophylaxis, reported Everett H. Meyer, MD, PhD, from the Stanford (Calif.) University.
“Orca-T has good evidence for reduced acute graft-versus-host disease, reduced chromic graft-versus-host disease, and a low nonrelapse mortality,” he said at the Transplant & Cellular Therapies Meetings.
The product can be quickly manufactured and delivered to treatment centers across the continental United States, with “vein-to-vein” time of less than 72 hours, he said at the meeting held by the American Society for Blood and Marrow Transplantation and the Center for International Blood and Marrow Transplant Research.
Orca-T consists of highly purified, donor-derived T-regulatory (Treg) cells that are sorted and delivered on day 0 with hematopoietic stem cells, without immunosuppressants, followed 2 days later with infusion of a matching dose of conventional T cells.
“The Treg cells are allowed to expand to create the right microenvironment for the [conventional T cells],” he explained.
In preclinical studies, donor-derived, high-purity Tregs delivered prior to adoptive transfer of conventional T cells prevented GVHD while maintaining graft-versus-tumor immunity, he said.
Two T-cell infusions
He reported updated results from current studies on a total of 50 adults, with a cohort of 144 patients treated concurrently with standard of care as controls.
The Orca-T–treated patients had a median age of 47 and 52% were male. Indications for transplant included acute myeloid and acute lymphoblastic leukemia, chronic myeloid leukemia, B-cell lymphoma, myelodysplastic syndrome/myelofibrosis, and other unspecified indications.
In both the Orca-T and control cohorts, patients underwent myeloablative conditioning from 10 to 2 days prior to stem cell infusion.
As noted patients in the experimental arm received infusion of hematopoietic stem/progenitor cells and Tregs, followed 2 days later by conventional T-cell infusion, and, on the day after that, tacrolimus at a target dose of 4.6 ng/mL. The conventional T cells were reserved from donor apheresis and were otherwise unmanipulated prior to infusion into the recipient, Dr. Meyer noted.
Patients in the standard-of-care arm received tacrolimus on the day before standard infusion of the apheresis product, followed by methotrexate prophylaxis on days 1, 3, 6 and 11.
Time to neutrophil engraftment, platelet engraftment, and from day 0 to hospital discharge were all significantly shorter in the Orca-T group, at 12 versus 14 days (P < .0001), 11 vs. 17 days (P < .0001), and 15 vs. 17 days (P = .01) respectively.
At 100 days of follow-up, the rate of grade 2 or greater acute GVHD was 30% among standard-of-care patients versus 10% among Orca-T–treated patients. At 1-year follow-up, respective rates of chronic GVHD were 46% vs. 3%.