With the use of posttransplant cyclophosphamide (PTCy), haploidentical donors have become an option for stem cell transplant (SCT) when no human leukocyte antigen (HLA)-matched donors are available. Nevertheless, these transplants are still plagued by high rates of chronic graft-versus-host disease (cGVHD) and relapse during reduced regimens of PTCy.
A new, promising cell therapy from Orca Bio Manufacturing, Sacramento, California, called Orca-Q, could circumvent the need for PTCy in haplo-SCT. Orca-Q consists of enriched CD34+ stem cells and “specific T-cell subsets.” It may be administered as a single prophylactic agent.
A multi-institutional clinical research team led by Samer A. Srour of the University of Texas MD Anderson Cancer Center presented the results of the expansion arm of a phase I trial at the 2023 Tandem Meetings of ASTCT and CIBMTR.
For this arm of the study, the team enrolled 21 patients age 18-65 years old with either acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), or chronic lymphocytic leukemia (CLL) with blast phase who were eligible for myeloablative conditioning SCT from haploidentical donors. All received single-agent GVHD prophylaxis with tacrolimus from day -1 to taper beginning on day +60.
The disease risk index (DRI) score was very high in 5 patients and intermediate in 13 patients. All patients were engrafted (median 13 days for neutrophil and 16 days for platelet engraftment). Grade 3 acute GVHD occurred in 1 patient; none had grade 4 acute GVHD. Sixteen patients had >3-month follow-up, and only 1 of those patients had mild cGVHD. No patients had moderate-to-severe cGVHD. The patients followed for 1 year had a 71% GVHD- and relapse-free survival.
“Our findings suggest encouraging safety and efficacy outcomes using Orca-Q cell therapy for haplo-SCT, without PTCy, and only single agent tacrolimus,” reported the researchers.
Srour SA, Salhotra A, Lowsky R, et al. Orca-Q demonstrates favorable GvHD-and-relapse-free survival with haploidentical donors without post-transplant cyclophosphamide. Abstract #33. Presented at the 2023 Tandem Meetings of ASTCT and CIBMTR; February 15-19, 2023; Orlando, FL.