Addition of JSP191 (C-kit Antibody) to Nonmyeloablative Hematopoietic Cell Transplantation for Sickle Cell Disease and Beta-Thalassemia

300 cGy total body irradiation (TBI, day -2)

Optimized 4-12 weeks prior to planned transplant date

briquilimab, anti-CD117 monoclonal antibody at 0.6mg/kg at day -11 prior to infusion of allogeneic HSCs

May be used to minimize the days of neutropenia, and may be administered beginning near day 10 post stem cell infusion at 5 mcg/kg (rounding to the nearest vial) at the discretion of investigator.

For immune suppression (day -1)

Alemtuzumab 1 mg/kg of alemtuzumab divided over 5 days (-7 through -3),

For autologous HSC collection; dose of plerixafor at 240 mcg/kg (capped at 20mg)