Restoration of β-globin expression with optimally designed lentiviral vector for β-thalassemia treatment in Chinese patients

Abstract β-thalassemia is one of the most prevalent genetic diseases worldwide. The current treatment for β–thalassemia is allogeneic hematopoietic stem cell transplantation (HSCT), which is limited due to lack of matched donors. Gene therapy has been developed as an alternative therapeutic option for transfusion-ependent β -thalassemia (TDT). However, successful gene therapy for β -thalassemia patients in China has not been reported. Here we present the results of preclinical studies of an optimally designed LV named LentiHBB T87Q in hematopoietic stem cells (HSCs) 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 β-globin gene (HBB T87Q ) driven by a specific reconstituted locus control region (rLCR) and efficiently express HBB mRNA and HBB protein in erythroblasts derived from cord blood (CB) HSCs. 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 (HbA) tetramer to relatively normal level in erythroblasts from bone marrow (BM) HSCs of Chinese TDT patients, that carry the most common mutation types and cover various genotypes, including β 0/ β 0. Furthermore, viral integration sites (VIS) of cLentiHBB T87Q were similar to other LVs safely used in previous clinical trials and the associated risk of tumorigenesis was not observed in cLentiHBB T87Q transduced HSCs through comprehensive analysis. Taken together, we have engineered the cLentiHBB T87Q that can restore β-globin expression in the HSCs-derived erythroblasts of Chinese TDT patients with minimal risk on tumorigenesis, providing a favorable starting point for future clinical application.