HOUSTON – A novel anti-CD45 targeted conditioning regimen is feasible for use in older patients with relapsed or refractory acute myeloid leukemia undergoing transplant, according to preliminary results of a randomized, phase 3 trial.
Treatment with iodine-131 apamistamab (Iomab-B) has thus far has resulted in successful engraftment for all patients who have received it and gone on to transplant, despite active disease and high bone marrow blast burden prior to transplantation, according to Sergio A. Giralt, MD, of Memorial Sloan Kettering Cancer Center, New York.
There has been no nonrelapse mortality related to the novel regimen in the ongoing trial, which compares Iomab-B as targeted conditioning prior to allogeneic hematopoietic stem cell transplant (HCT) with standard of care regimens, Dr. Giralt said in an update on the trial, known as SIERRA.
SIERRA is the only ongoing, randomized, phase 3 clinical trial to offer a transplant option in patients aged 55 years or older with active relapsed or refractory acute myeloid leukemia (AML), Dr. Giralt said at the Transplantation & Cellular Therapy Meetings.
“This is an underserved population in which traditional transplant techniques have very poor results, and there are limited options for patients with active disease,” Dr. Giralt said. “Of note, many transplant centers today do not consider these patients eligible for transplant.”
A total of 150 patients are to be enrolled in SIERRA and randomized either to investigator’s choice of salvage induction chemotherapy including approved targeted agents or to the experimental arm, which consists of an individualized dose of Iomab-B 12 days prior to HCT with fludarabine and total body irradiation as transplant conditioning.
Dr. Giralt presented an update on the first 38 patients in SIERRA, representing 25% of the total enrollment target.
Of 18 patients randomized to Iomab-B and transplanted, the median number of days to absolute neutrophil count engraftment was 13, Dr. Giralt said.
In the control arm, 15 of 19 (79%) failed to achieve complete remission, and of those 10 crossed over to receive Iomab-B and transplant. Days to engraftment, full donor chimerism, and dose delivered to the bone marrow were all similar in the crossover group, compared with those initially randomized to the novel therapy.
Nonhematologic grade 3 or 4 toxicities were similar between the Iomab-B arm and the conventional care arm, and included febrile neutropenia, stomatitis, and other side effects typical for these patients.
There were no grade 3 or 4 Iomab-B infusion-related reactions, and four mild cases of chronic graft-versus-host disease occurred in Iomab-B treated patients.
Nonrelapse mortality was “extremely low” with no cases in the 100 days post transplant in those initially randomized to Iomab-B, and only one case in a crossover patient, Dr. Giralt said.
“These results are encouraging, and can broaden transplant eligibility and improve outcomes,” he added.
The meeting is held by the American Society for Blood and Marrow Transplantation and the Center for International Blood and Marrow Transplant Research. At its meeting, the American Society for Blood and Marrow Transplantation announced a new name for the society: American Society for Transplantation and Cellular Therapy (ASTCT).
The SIERRA study is supported by Actinium Pharmaceuticals. Dr. Giralt reported disclosures related to Actinium and several other companies.
SOURCE: Giralt SA et al. TCT 2019, Abstract LBA3.