Peptide Sequence Determines the Efficacy of Single-Dose AAV-Vectorized GLP-1R Agonists in Diet-Induced Obese Mice
Background: Glucagon-like peptide-1 receptor (GLP-1R) agonists such as semaglutide produce substantial weight loss and glycemic improvement, but their long-term efficacy depends on sustained adherence to chronic dosing. Adeno-associated virus (AAV) gene therapy could, in principle, provide durable GLP-1R agonist (GLP-1RA) exposure from a single administration, but the degree of peptide engineering required for a vectorized GLP-1RA transgene to be efficacious in vivo is unknown. Methods: We generated four self-complementary AAV (scAAV) constructs encoding: native human GLP-1(7-36) (GLP-1), a DPP-IV-resistant Gly8-GLP-1(7-36) variant (Gly8), Exendin-4 (Ex4), or an Exendin-4 human IgG4 Fc fusion protein (Ex4-Fc). All four constructs were validated to secrete functional GLP-1R agonists in vitro using a conditioned-media potency assay. Subsequently, these constructs were packaged into PHP.eB capsids and administered as a single intravenous dose (5x1012 vg/kg) to diet-induced obese (DIO) mice alongside a vehicle control. Body weight, body composition, food intake, fasting plasma insulin, and oral glucose tolerance were assessed over a 3-week period. At the end of the study, tissues were harvested for assessments of plasma/liver lipids, tissue transgene transcript and peptide levels. Results: HEK293 cells transfected with the four AAV constructs all secreted active peptides/proteins as assessed by a cell-based GLP-1R activation assay, although the effective concentration of the GLP-1 constructs in the media spanned nearly four orders of magnitude 72 hours after transfection. In diet-induced obese (DIO) mice, Ex4 and Ex4-Fc vectors, but not GLP-1 or Gly8 vectors, produced significant reductions in body weight of up to 22.6% of starting body weight out to 21 days after a single dose. In addition, reductions in food intake, fat mass, and fasting insulin relative to vehicle were also observed for Ex4 and Ex4-Fc. Furthermore, Ex4-Fc improved oral glucose tolerance while reducing plasma cholesterol and liver triglycerides relative to vehicle. Although transcript levels did not differ appreciably among the four constructs in either brain or liver, measurable peptide product in plasma and brain lysate tracked the rank order of the in vitro supernatant screen, with GLP-1 and Gly8 groups indistinguishable from endogenous background. Conclusions: PHP.eB scAAV Ex4 and Ex4-Fc showed robust efficacy on multiple metabolic endpoints including weight loss and glucose tolerance. In contrast, vectorized GLP-1 and Gly8 showed no in vivo efficacy despite comparable levels of viral transcript in the brain and the liver. Vectorized GLP-1 and Gly8 also performed poorly compared to exendin-4-based constructs in vitro, suggesting that conditioned-media potency screening is a valid early filter for construct selection in vectorized-peptide AAV development. Engineering peptides to improve translation and secretion efficiency, in addition to circulating plasma stability, could further optimize vectorized GLP-1RA therapeutics.