Phase I/II Trial of StemRegenin-1 Expanded Umbilical Cord Blood Hematopoietic Stem Cells Supports Testing as a Stand-Alone Graft

Clinical application of umbilical cord blood (UCB) as a source of hematopoietic stem cells for transplantation is limited by low CD34+ cell dose, increased risk of graft failure, and slow hematopoietic recovery. While the cell dose limitation is partially mitigated by using two UCB units, larger-dosed single units would be preferable. We have evaluated the feasibility and safety of StemRegenin-1 (SR-1), an aryl hydrocarbon receptor antagonist that expands CD34+ cells, by placing one of the two units in expansion culture. SR-1 produced a 330-fold increase in CD34+ cells and led to engraftment in 17/17 patients at a median of 15 days for neutrophils and 49 days for platelets, significantly faster than in patients treated with unmanipulated UCB. Taken together, the marked expansion, absence of graft failure, and enhanced hematopoietic recovery support testing of SR-1 expansion as a stand-alone graft and suggest it may ameliorate a limitation of UCB transplant. [Display omitted] •SR-1 led to significant expansion of CD34+ HSPCs in culture•Seventeen patients with hematological malignancy received SR-1 expanded UCB•SR-1 expanded cells were co-infused with a second unexpanded UCB unit•SR-1 expansion improved neutrophil and platelet recovery compared to controls Clinical testing of the aryl hydrocarbon antagonist StemRegenin-1 showed robust expansion of hematopoietic stem and progenitor cells and an adequate safety profile in the setting of double UCB transplant, supporting its further testing for safety and efficacy as a stand-alone graft after myeloablative conditioning.