A Novel High-Titer, Bifunctional Lentiviral Vector for Autologous Hematopoietic Stem Cell Gene Therapy of Sickle Cell Disease

A major limitation of gene therapy for sickle cell disease (SCD) is the availability and access to a potentially curative one-time treatment, due to high treatment costs. We have developed a high -titer bifunctional lentiviral vector (LVV) in a vector backbone that has reduced size, high vector yields, and ef fi cient gene transfer to human CD34 + hematopoietic stem and progenitor cells (HSPCs). This LVV contains locus control region cores expressing an anti-sickling b AS3 -globin gene and two microRNAadapted short hairpin RNA simultaneously targeting BCL11A and ZNF410 transcripts to maximally induce fetal hemoglobin (HbF) expression. This LVV induces high levels of anti-sickling hemoglobins (HbA AS3 + HbF), while concurrently decreasing sickle hemoglobin (HbS). The decrease in HbS and increased anti-sickling hemoglobin impedes deoxygenated HbS polymerization and red blood cell sickling at low vector copy per cell in transduced SCD patient CD34 + cells differentiated into erythrocytes. The dual alterations in red cell hemoglobins ameliorated the SCD phenotype in the SCD Berkeley mouse model in vivo . With high titer and enhanced transduction of HSPC at a low multiplicity of infection, this LVV will increase the number of patient doses of vector from production lots to decrease costs and help improve accessibility to gene therapy for SCD.