Multiple Integrated Non-clinical Studies Predict the Safety of Lentivirus-Mediated Gene Therapy for β-Thalassemia

Abstract

Gene therapy clinical trials require rigorous non-clinical studies in the most relevant models to assess the benefit-to-risk ratio. To support the clinical development of gene therapy for β-thalassemia, we performed in vitro and in vivo studies for prediction of safety. First we developed newly GLOBE-derived vectors that were tested for their transcriptional activity and potential interference with the expression of surrounding genes. Because these vectors did not show significant advantages, GLOBE lentiviral vector (LV) was elected for further safety characterization. To support the use of hematopoietic stem cells (HSCs) transduced by GLOBE LV for the treatment of β-thalassemia, we conducted toxicology, tumorigenicity, and biodistribution studies in compliance with the OECD Principles of Good Laboratory Practice. We demonstrated a lack of toxicity and tumorigenic potential associated with GLOBE LV-transduced cells. Vector integration site (IS) studies demonstrated that both murine and human transduced HSCs retain self-renewal capacity and generate new blood cell progeny in the absence of clonal dominance. Moreover, IS analysis showed an absence of enrichment in cancer-related genes, and the genes targeted by GLOBE LV in human HSCs are well known sites of integration, as seen in other lentiviral gene therapy trials, and have not been associated with clonal expansion. Taken together, these integrated studies provide safety data supporting the clinical application of GLOBE-mediated gene therapy for β-thalassemia.

Myelodysplastic syndrome unrelated to lentiviral vector in a patient treated with gene therapy for sickle cell disease

“…LVV gene therapy has been safe in animal models, [8][9][10][11] and there have been no published cases of insertional oncogenesis in patients thus far. 6,[12][13][14][15] The patient received HU for several years, Cells were collected from the patient at diagnosis (PB), 20 days postdiagnosis of MDS (BM), and 8 days post-AML recurrence (PB and BM).…”

Novel genetic therapeutic approaches for modulating the severity of β‑thalassemia (Review)

“…Additional clinical studies are required to determine whether there are any interactions between the viral vectors and the genome of the patient, and the effects of such interactions. In β-thalassemia gene therapy, due to erythroid-restricted activity of promoters, there is a very low probability of genotoxicity caused by trans-activation (67). Thus, no toxicity or tumor production has been reported in studies where lentiviral vectors were used in mouse models.…”

“…Thus, no toxicity or tumor production has been reported in studies where lentiviral vectors were used in mouse models. However, checks are required to ensure the vector has not inserted, the toxicity of the vector and germline transfer (67). A recent study showed that the absence of transplant based mortality as well as replication of competent lentiviruses resulted in other complications, such as febrile neutropenia, epistaxis, stomatitis, pyrexia, irregular menstruation and liver diseases in some patients (68).…”

Gentherapie von Hämoglobinkrankheiten – aktuelle Konzepte und Herausforderungen

“…2-3 viralen Vektoren in das Wirtsgenom ist das Risiko einer Onkogenaktivierung damit ausgesprochen geringaber wahrscheinlich auch nicht null. So sind in einer zunehmenden Zahl von klinischen Studien mit lentiviralen Vektoren für die Behandlung unterschiedlicher genetischer Erkrankungen bislang noch keine durch die Integration der Viren verursachte Sekundärleukämien oder andere maligne Erkrankungen beobachtet worden [33,44,45]. Allerdings ist die Anzahl von behandelten Patienten noch klein (< 100) und die Dauer der Nachbeobachtung insgesamt noch kurz, sodass eine abschließende Bewertung des Risikopotenzials dieses Vektortypus heute noch nicht möglich ist.…”