FORT LAUDERDALE, FLA. — A multicenter pilot study of a prophylactic regimen for both matched sibling donor and unrelated donor bone marrow transplantation in adults with severe sickle cell disease has found similar overall and event-free survival rates between the two approaches, exceeding 90% and 85%, respectively, at one year, according to preliminary results presented at the annual meeting of the Foundation for Sickle Cell Disease Research.
The results have led to a Phase 2 single-arm, multicenter trial, known as, to evaluate a reduced toxicity preparative regimen consisting of busulfan (13.2 mg/kg), fludarabine (175 mg/m 2 ) and antithymocyte globulin (ATG, 6 mg/kg) and cyclosporine or tacrolimus and methotrexate for graft-vs-host disease (GVHD) prophylaxis in adults with sickle cell disease (SCD), said Lakshmanan Krishnamurti, MD, of Children’s Healthcare of Atlanta/Emory University. “The data are similar with 91% overall survival and 86% event-free survival,” he said.
The pilot study, published recently (), indicated the effectiveness of non-myeloablative conditioning in SCD patients with matched-sibling bone marrow transplant (BMT), with a higher intensity regimen of busulfan/fludarabine/ATG effective in unrelated donor BMT for other conditions, Dr. Krishnamurti said.
The pilot study also found that three-year event-free survival (EFS) of 82%, and statistically significant improvements in pain and health-related quality of life.
STRIDE is the first comparative study of BMT vs. standard of care in severe SCD, Dr. Krishnamurti added. The primary endpoint is overall survival at two years after biologic assignment, with longer-term outcomes including survival at three to 10 years post-hematopoietic stem cell transplantation (HSCT), and impact of BMT on sickle-related events, organ function, health-related quality of life and chronic pain.
The pilot study included 22 patients between the ages of 17 and 36 who had BMT at eight centers. Seventeen patients received marrow from a sibling-matched donor and five patients received marrow from an unrelated donor.
Dr. Krishnamurti referenced a recent study out of France that showed chimerism levels after transplant may be a determining physiological factor for outcomes (Haematologica.). “So if chimerism is stable, somewhere in the 25% to 50% or better range, and hemoglobin levels are improved, this decrease hemolysis,” he said. “This is very important in understanding how to manage these patients.”
That study showed that rates of chronic GVHD up to 10 years post-transplant have steadily improved over the past three decades in patients with SCD who’ve had BMT, Dr. Krishnamurti noted. “But chronic GVHD is higher in patients age 16 to 30 vs. patients 15 and younger,” he said, “so that’s the reason to consider transplantation sooner in patients who have a matched sibling donor.”
The French study shows that BMT with sibling-matched donors has excellent outcomes in young children, Dr. Krishnamurti said. “Outcomes for adults with transplantation is becoming similar to that in children,” he added. “Age is an important predictor of outcomes and the risk for progressive morbidity-impaired quality of life and risk of mortality still exists in adults with sickle cell disease.”
The bottom line, he said, is that patients and caregivers must be given the opportunity to consider transplantation as an option at younger ages.
Dr. Krishnamurti did not disclose any financial relationships.
SOURCE: Krishnamurti L et al. FSCDR 2019