Restoration Of Beta-Globin Expression With Optimally Designed Lentiviral Vector For Beta-Thalassemia Treatment In Chinese Patients

beta-Thalassemia is one of the most prevalent genetic diseases worldwide. The current treatment for beta-thalassemia is allogeneic hematopoietic stem cell transplantation, which is limited due to lack of matched donors. Gene therapy has been developed as an alternative therapeutic option for transfusion-dependent beta-thalassemia (TDT). However, successful gene therapy for beta-thalassemia patients in China has not been reported. Here, we present the results of preclinical studies of an optimally designed lentiviral vector (LV) named LentiHBB(T87Q) in hematopoietic stem and progenitor cells (HSPCs) derived from Chinese TDT patients. LentiHBB(T87Q) was selected from a series of LVs with optimized backbone and de novo cloning strategy. It contains an exogenous T87Q beta-globin gene (HBBT87Q) driven by a specific reconstituted locus control region, and efficiently expresses HBB mRNA and HBB protein in erythroblasts derived from cord blood HSPCs. To facilitate clinical transformation, we manufactured clinical-grade LentiHBB(T87Q) (cLentiHBB(T87Q)) and optimized its transduction procedure. Importantly, transduction of cLentiHBB(T87Q) restored expression of HBB monomer and adult hemoglobin tetramer to relatively normal level in erythroblasts from bone marrow HSPCs of Chinese TDT patients that carry the most common mutation types and cover various genotypes, including beta 0/beta 0. Furthermore, viral integration sites (VISs) of cLentiHBB(T87Q) were similar to other LVs safely used in previous clinical trials, and gene-ontology (term) analysis of VIS targeted genes suggests that no tumor-associated pathways were enriched in treated samples. Taken together, we have engineered the cLentiHBB(T87Q) that can restore beta-globin expression in the HSPCs-derived erythroblasts of Chinese TDT patients with minimal risk of tumorigenesis, providing a favorable starting point for future clinical application.