GroβT rapidly and reliably mobilizes primitive hematopoietic stem and progenitor cells in nonhuman primates

Autologous hematopoietic stem cell (HSC) gene therapy has gone through remarkable advancements in recent years, especially for the treatment of sickle cell disease (SCD). However, the collection of HSCs from SCD patients requires unique considerations, as granulocyte colony-stimulating factor (G-CSF)-mediated mobilization is contraindicated, and plerixafor-only mobilization is highly variable. Consequently, alternative mobilization regimens that are safe for SCD patients and generate better cell yields are desirable for SCD HSC gene therapy. Here, we evaluated a combination of plerixafor (AMD3100, a CXCR4 antagonist) with GroβT (MGTA-145/GroβT, a CXCR2 agonist) against the current gold-standard G-CSF for HSC gene therapy in nonhuman primates (NHPs) for HSC mobilization, leukapheresis, ex vivo gene editing to reactivate fetal hemoglobin, and transplantation. AMD3100/GroβT rapidly and reliably mobilized phenotypically primitive HSCs within hours even in a G-CSF non-responder. Average CD34/CD90 frequency in the blood and yields after enrichment were comparable in both mobilization regimens. Rapid recovery and robust multilineage long-term engraftment of gene-modified HSCs was achieved in the bone marrow and blood of animals. In summary, AMD3100/GroβT allows highly efficient and reliable mobilization of HSCs, providing a G-CSF-free regimen specifically for SCD but also any other hematological disease or disorder treatable with HSC gene therapy.