Sickle Cell Disease Transplant Using a Nonmyeloablative Approach for Patients With Anti-donor Red Cell Antibody

This study addresses an important question: Can daratumumab safely be administered prior to matched sibling donor (MSD) nonmyeloablative hematopoietic cell transplant (HCT) for SCD to avoid pure red blood cell aplasia in patients at risk of this complication? and thus achieve an event-free survival similar to patients without anti-donor red blood cell (RBC) antibodies?

Patients with anti-donor RBC antibodies, which includes patients with major ABO mismatch and other RBC alloantibodies against donor, have largely been excluded from the nonmyeloablative HCT approach given their risk of delayed donor RBC engraftment and/or hemolysis post-HCT. Exclusion of these patients limits access to less toxic curative therapies for this population at risk for toxicity due to their underlying multisystem disease. To address this need, we propose a multicenter clinical trial of Sickle cell disease Using a Nonmyeloablative approach: adding daratumumab for patients with anti-donor Red cell AntibodY (SUN-RAY). If successful, this trial will increase access to MSD nonmyeloablative HCT in SCD and will provide important safety and efficacy data for the use of daratumumab in the pre-HCT setting as well as in patients with SCD who have limited RBC donor options due to alloimmunization.

This is a phase 2 study given that the studied nonmyeloablative conditioning backbone (alemtuzumab, 300 cGY TBI, sirolimus) has been previously used effectively in both adults and children with SCD. Daratumumab will be added to this backbone with a washout period of 4 weeks prior to HCT infusion. Small case series have demonstrated that daratumumab is well tolerated either pre-HCT to treat patients with antibodies against mismatched donor HLA antigens, or post-HCT in patients with autoimmune cytopenias. The experience of the phase 2 clinical trial NCT03384654 studying daratumumab in pediatric acute lymphoblastic leukemia provides additional support for the safety and dosing of daratumumab for this study.