Subcutaneous administration of adipose-tropic gene therapy for congenital leptin deficiency

AAV-based gene therapy targeting adipose tissue has been underdeveloped due to lack of adipose-tropic AAV vectors with sufficient transduction efficiency. We previously demonstrated that an engineered capsid variant of Rec2 capsid with F503Y, Y708D and K709I substitution (named V7 capsid) exhibited highly selective adipo-tropism while ablating liver transduction upon intraperitoneal injection or intravenous injection. In this study, we investigated the feasibility of subcutaneous administration of V7 vector harboring human leptin (V7-LEP) in a congenital leptin deficiency model ob/ob mice. Subcutaneous administration of V7-LEP vector at a low dose of 4×10¹⁰ viral genome per mouse restored circulating leptin levels and completely normalized metabolic abnormalities associated with leptin deficiency. In an ongoing long-term experiment, one-time subcutaneous administration of V7-LEP to extreme obese ob/ob mice has led to sustained weight loss at least up to 9 months post injection associated with stable circulating human leptin levels throughout the long-term study. These data indicate subcutaneous injection is a feasible and relevant administration route for gene therapy targeting adipose tissue, and V7-LEP is highly efficacious for congenital leptin deficiency and potentially other lipodystrophy disorders with leptin deficiency.