Introduction
The pancreas plays an important role in metabolic regulation. Diseases such as diabetes and obesity may benefit from local therapeutic delivery to improve on-target efficacy, safety, and durability while limiting off-target safety risks. Advancements in adeno-associated virus (AAV)-based technologies have expanded the applicability of gene therapy as a one-time treatment strategy for metabolic diseases. Local AAV delivery has the potential to revolutionize gene therapy treatment if it can be delivered safely. We developed a novel AAV-based gene therapy platform and proprietary endoscopic ultrasound (EUS)-guided automated delivery system that directly targets the pancreas, maximises AAV activity, and minimises safety concerns.
Aims & Methods
The aim of this study was to assess the feasibility and safety of infusing AAV gene therapy into the pancreas in a Yucatan pig model. A linear echoendoscope and 25-gauge needle integrated with an automated fluid delivery system were used to optimize the infusion of AAV into the pancreatic splenic lobe (porcine equivalent to human pancreas body and tail). Toluidine blue (TBO) dye, vehicle, and AAV-driven green fluorescent protein (GFP) expression were used to evaluate procedural parameters, safety, and pancreatic distribution. Necropsies were performed at 1 hour post-TBO (n=4) and 3-4 weeks post-AAV (n=11) and vehicle infusions (n=2). Pancreatic tissue was collected for characterisation of either TBO dye, AAV genomes, or AAV-GFP expression to confirm on-target efficiency. Serum alanine transaminase (ALT) and lipase were evaluated from baseline up to 4 weeks post-procedure to establish procedural safety.
Results
In TBO-infused pigs, dye was extensively distributed throughout the targeted region with minimal distribution in untargeted regions indicating that established device and procedural parameters could effectively target the splenic lobe of the pancreas. AAV-GFP infusion demonstrated localised dose-dependent biodistribution in the pancreas with robust activity in up to 80% of cells in the targeted splenic lobe as evidenced by histological GFP expression at 3 weeks post-procedure (62±10% SEM, n=4, highest dose=1.5e14 vector genome [VG]). Untargeted duodenal and connecting pancreatic lobes showed minimal GFP expression underscoring the on-target efficiency of the device and procedure. Over the course of the study, 17 pigs were successfully infused with no sign of procedure-related adverse events or acute pancreatitis. Mean serum ALT remained in the normal range across all time points measured. Mean serum lipase remained in the normal range across most timepoints evaluated with a transient elevation (~2.5x above baseline) detected at 4 hours post-procedure in one AAV-treated animal, which resolved by 72 hours. At 3-4 weeks post-procedure, elevations in serum lipase were detected and attributed to durable expression and immunogenicity of the foreign GFP reporter as pancreatic GFP expression and lipase were significantly correlated (r=0.60, p=0.032, N=13).
Conclusion
This study provides proof of concept that a novel EUS-guided automated delivery system for gene therapy can effectively target the pancreas with an encouraging preliminary safety profile. This local gene therapy approach may provide a new platform for one-time, durable treatment of metabolic diseases including diabetes and obesity.
Disclosure
CCT: consultant/research support–Apollo Endosurgery, Olympus/Spiration, GI Dynamics, Boston Scientific, Endoquest Robotics, FujiFilm, Lumendi; consultant/advisory board–Fractyl, Xenter; consultant/advisory board/research support–USGI Medical; consultant–Medtronic; research support–Aspire Bariatrics, ERBE; founder/consultant/board member–Enterasense Ltd, EnVision Endoscopy; founder/board member/ownership interest–GI Windows; general partner–BlueFlame Healthcare Venture Fund. JW, APL, EC, JC, and HR: employees and shareholders of Fractyl Health, Inc. LSL and RPT: consultants for Fractyl Health, Inc.
