Lentiviral Vectors for Hematopoietic Stem Cell Gene Therapy Restore α-Globin Expression in α-Thalassemia Red Blood Cells

Alpha thalassemia major (ATM) is an inherited blood disorder caused by the absence of all four α-globin genes (HBA2/1), resulting in severe anemia and lifelong transfusion dependence. While allogeneic hematopoietic stem cell transplant (HSCT) offers a potential cure, donor availability remains limited. We present a gene therapy approach for autologous HSCT, using lentiviral vectors (LVs) to deliver HBA2 under the regulation of optimized β-globin locus control region (LCR) enhancers, restoring α-globin expression. The best-performing LVs, EV-α and EV-α-UV, achieved 90-100% transduction efficiency in human hematopoietic stem and progenitor cells (HSPCs), optimal vector copy numbers, and a safe integration profile. ATM-derived HSPCs from three donors treated with these LVs yielded α/β-globin mRNA and chain ratios within the therapeutic range (~0.5+), and restored hemoglobin levels by 50 to 100%. These findings establish the safety and clinical potential of EV-α and EV-α-UV as a promising autologous stem cell gene therapy for ATM. Erythroid cells differentiated from bone marrow derived hematopoietic stem and progenitor cells from 2 healthy donors and 1 donor with alpha thalassemia major. Some conditions from the alpha thalassemia major cells were transduced with different alpha globin lentiviral vectors desgined and produced in our laboratory.