Assessment of safety and immunogenicity of MHC homozygous iPSC-derived CD34+ hematopoietic progenitors in an NHP model

Administration of ex vivo expanded somatic myeloid progenitors has been explored as a way to facilitate a more rapid myeloid recovery and improve overall survival after myeloablation. Recent advances in induced pluripotent stem cell (iPSC) technologies have created alternative platforms for supplying off-the-shelf immunologically compatible myeloid progenitors, including cellular products derived from major histocompatibility complex (MHC) homozygous superdonors, potentially increasing the availability of MHC-matching cells and maximizing the utility of stem cell banking. However, the teratogenic and tumorigenic potential of iPSC-derived progenitor cells and whether they will induce alloreactive antibodies upon transfer remain unclear. We evaluated the safety and efficacy of using CD34+CD45+ hematopoietic progenitors derived from MHC homozygous iPSCs (iHPs) to treat cytopenia after myeloablative hematopoietic stem cell (HSC) transplantation in a Mauritian cynomolgus macaque (MCM) nonhuman primate (NHP) model. We demonstrated that infusion of iHPs was well tolerated and safe, observing no teratomas or tumors in the MCMs up to 1 year after HSC transplantation and iHP infusion. Importantly, the iHPs also did not induce significant levels of alloantibodies in MHC-matched or -mismatched immunocompetent MCMs, even after increasing MHC expression on iHPs with interferon-γ. These results support the feasibility of iHP use in the setting of myeloablation and suggest that iHP products pose a low risk of inducing alloreactive antibodies.