Safety
“In general, the protocol is extremely well tolerated by our patients. We’ve seen no exceptional infectious disease complications, and we’ve seen no other major complications,” Dr. Meyer said.
Cytomegalovirus prophylaxis was used variably, depending on the center and on the attending physician. Epstein-Barr virus reactivation occurred in eight patients, with one requiring therapy, but there was no biopsy or radiographic evidence of posttransplant lymphoproliferative disorder.
In all, 18% of patients had serious adverse events during the reporting period, all of which resolved. There were no treatment-related deaths in the Orca-T arm, compared with 11% of controls.
Engraftment differences explored
In the question-and-answer session following the presentation, Christopher J. Gamper, MD, PhD, from the Johns Hopkins Hospital in Baltimore, told Dr. Meyer that “your outcomes from Orca-T look excellent,” and asked about the cost differential, compared with similar, unmanipulated transplants performed with standard GVHD prophylaxis.
“Is this recovered by lower costs for treatment of GVHD?” he asked.
“I have not done an economic cost analysis of course, and I think others may be looking into this,” Dr. Meyer replied. “Graft engineering can be expensive, although it’s an engineering proposition and one could imagine that the costs will go down substantially over time.”
Session moderator Alan Hanash, MD, PhD, from Memorial Sloan Kettering Cancer Center in New York, commented on the differences in engraftment between the experimental controls arms, and asked Dr. Meyer: “Do you think this is due to the difference in prophylaxis? Absence of methotrexate? Do you think that it could be a direct impact of regulatory T cells on hematopoietic engraftment?”
“Certainly not having methotrexate is beneficial for engraftment, and may account for the differences we see, Dr. Meyer said. “However, it is possible that Tregs could be playing a facilitative role. There certainly is good preclinical literature that Tregs, particularly in the bone marrow space, can facilitate bone marrow engraftment.”
The Orca-T trials are sponsored by Orca Bio and Stanford, with support from the National Institutes of Health. Dr. Meyer receives research support from Orca and is a scientific adviser to GigaGen, Triursus, Incyte, and Indee Labs. Dr. Hanash and Dr. Gamper had no relevant disclosures.