Generation of a Porcine Antibody Fab Fragment Using Protein Engineering to Facilitate the Evaluation of Ocular Sustained Delivery Technology

Treatment of age-related macular degeneration (AMD) with anti-vascular endothelial growth factor (VEGF) biologicagents has been shown to restore and maintain visual acuity for many patients afflicted with wet AMD. These agents are usuallyadministered via intravitreal injection at a dosing interval of 4-8 weeks. Employment of long-acting delivery (LAD) technologiescould improve the therapeutic outcome, ensure timely treatment, and reduce burden on patients, caregivers, and the health caresystem. Development of LAD approaches requires thorough testing in pre-clinical species; however, therapeutic proteins of humanorigin may not be well tolerated during testing in non-human species due to immunogenicity. Here, we have engineered a surrogateporcine antibody Fab fragment (pigG6.31) from a human antibody for testing ocular LAD technologies in a porcine model. Theengineered Fab retains the VEGF-A-binding and inhibition properties of the parental human Fab and has stability properties suitablefor LAD evaluation. Upon intravitreal injection in minipigs, pigG6.31 showedfirst-order clearance from the ocular compartmentswith vitreal elimination rates consistent with other molecules of this size. Application of the surrogate molecule in an in vivoevaluation in minipigs of a prototype of the port delivery (PD) platform indicated continuous ocular delivery from the implant, withrelease kinetics consistent with both the results from in vitro release studies and the efficacy observed in human clinical studies of thePD system with ranibizumab (PDS). Anti-drug antibodies in the serum against pigG6.31 were not detected over exposure durationsup to 16 weeks, suggesting that this molecule has low porcine immunogenicity