Preclinical Evaluation of Efficacy and Safety of an Improved Lentiviral Vector for the Treatment of β-Thalassemia and Sickle Cell Disease

Abstract

A previously published clinical trial demonstrated the benefit of autologous CD34+ cells transduced with a self-inactivating lentiviral vector (HPV569) containing an engineered β-globin gene (βA-T87Q-globin) in a subject with β-thalassemia major. This vector has been modified to increase transduction efficacy without compromising safety. In vitro analyses indicated that the changes resulted in both increased vector titers (3 to 4 fold) and increased transduction efficacy (2 to 3 fold). An in vivo study in which 58 β-thalassemic mice were transplanted with vector- or mock-transduced syngenic bone marrow cells indicated sustained therapeutic efficacy. Secondary transplantations involving 108 recipients were performed to evaluate long-term safety. The six month study showed no hematological or biochemical toxicity. Integration site (IS) profile revealed an oligo/polyclonal hematopoietic reconstitution in the primary transplants and reduced clonality in secondary transplants. Tumor cells were detected in the secondary transplant mice in all treatment groups (including the control group), without statistical differences in the tumor incidence. Immunohistochemistry and quantitative PCR demonstrated that tumor cells were not derived from transduced donor cells. This comprehensive efficacy and safety data provided the basis for initiating two clinical trials with this second generation vector (BB305) in Europe and in the USA in patients with β-thalassemia major and sickle cell disease.

Novel players in β-thalassemia dyserythropoiesis and new therapeutic strategies

“…The latter approach has been successfully applied to three French patients [27]. Finally, suppressing the subunit that is produced in excess in hemoglobinopathies (i.e., b-chains in HbH disease and a-chains in b-thalassemia) is another approach well worth exploring.…”

Lentiviral Transfer of γ-Globin with Fusion Gene NUP98-HOXA10HD Expands Hematopoietic Stem Cells and Ameliorates Murine β-Thalassemia

“…14,30 Briefly, 100 ng of genomic DNA was derived from 6-month-old transplanted mice. LAM PCR was performed in the following manner: biotin labeled oligo (5 0 -AGGGTCTGAGGGATCTCTAGTTAC) was used for the initial 50 cycles of linear PCR.…”

“…10 Many different approaches were investigated to improve the efficiency of transduction and engraftment with the goal of increasing the number of genetically modified cells in peripheral blood. [11][12][13][14][15][16] One such approach is to express a HOX protein that confers a benign proliferative advantage to the modified cells over the non-transduced cells in vivo. 15,17,18 HOXB4 was the first HOX family member found to enhance the expansion of human and mouse HSCs by promoting self-renewal divisions without losing stemness.…”

Treating hemoglobinopathies using gene-correction approaches: promises and challenges

“…In addition, the promoter-enhancer was changed from the 5’ HIV U3-LTR to CMV, resulting in further enhancement in the viral titers and yields. In vitro comparison of the two vector designs revealed that the BB305 LentiGlobin provided 3-4 fold higher viral titers and a 2-3 fold higher vector copy number in transduced CD34 + cells relative to the HPV569 vector (Negre et al 2015). In a murine bone marrow transplant study, peripheral blood from mice engrafted with transduced BB305 LentiGlobin had a 1.1-1.5 fold higher vector copy number relative to the HPV569 vector.…”