Hematopoietic Cell Transplant compared with Standard Care in Adolescents and Young Adults with Sickle Cell Disease

• Short-term mortality after HCT was not excessive compared with standard care for SCD

• Patients with SCD experienced fewer pain crises and improved patient-reported outcomes after HCT, compared with standard care.care.

Disease-modifying therapies are standard of care (SOC) for sickle cell disease (SCD), but hematopoietic cell transplantation (HCT) has curative potential. We compared outcomes prospectively through 2-years after biologic assignment to a Donor or No Donor (SOC) Arm based on the availability of an HLA-matched sibling or unrelated donor (BMTCTN 1503; NCT02766465). A donor search was commenced after eligibility confirmation. The primary endpoint was the comparison of survival 2 years after biologic assignment between treatment arms. Power calculations required 60 participants on the Donor Arm and 140 on the No Donor Arm to determine if early transplant-related mortality might be balanced by disease-related mortality over a longer period of follow-up. Secondary objectives compared changes in SCD-related events, functional outcomes, and organ function. Data were analyzed by the intent-to-treat principle. A total of 113 participants were enrolled, 28 on the Donor and 85 on the No Donor Arm The 2-year probabilities of survival were 89% and 93%, on the Donor and No Donor Arms, respectively. Vaso-occlusive pain (VOC) was less frequent on the Donor Arm in the second year after biologic assignment (p < 0.001). On PROMIS-57 surveys there was decreased fatigue (p=0.003) and an increased ability to participate in social roles and activities (p=0.003) on the Donor Arm 2-years after biologic assignment. Differences in other secondary outcomes did not reach statistical significance. Barriers to accrual prevented an objective comparison of survival. Assignment to the Donor Arm led to improvements in VOC, fatigue, and social function.