In vivo HSPC gene therapy of hemoglobinopathies without drug selection of corrected cells

Researchers have developed a novel in vivo gene therapy technique for hemoglobinopathies that eliminates the need for pharmacologic selection of corrected cells. This approach utilizes base and prime editing to introduce a nonpathogenic EPOR variant into hematopoietic stem/progenitor cells (HSPCs), which then allows for the preferential expansion of gene-corrected erythroid cells.

This method combines EPOR editing with three therapeutic strategies for correcting hemoglobinopathies: gamma-globin gene addition, gamma-globin reactivation, or correction of the sickle cell disease mutation. The therapy was delivered using tropism-modified helper-dependent adenoviral vectors that targeted HSPCs, allowing for simultaneous delivery of the EPOR-editing machinery and therapeutic components.

In vitro studies in an erythroid progenitor cell line and primary CD34+ cells showed that the EPORW439* variant provided a significant proliferative advantage to the therapeutically modified erythroid progenitors. In mice genetically modified to mimic beta/thalassemia, the EPORW439*-mediated erythrocyte production of erythropoietin (EPO) hypersensitivity, combined with a therapeutic gamma-globin transgene, resulted in 70% HbF-positive erythroid cells and substantial reversal of the disease-associated phenotype.

These improvements included reduced oxidative stress, near-complete elimination of splenic iron deposition, and reduced splenomegaly. Crucially, these beneficial effects were achieved with just a single intravenous administration of the vectors after mobilizing HSPCs and administering cytokine prophylaxis, without requiring any subsequent pharmacologic selection.

This innovative gene-editing strategy holds promise for enhancing the therapeutic potential of in vivo HSPC gene therapy for hemoglobinopathies.