Protein Stability and Photostability under In Vitro Vitreal Conditions - Implications for Long Acting Delivery of Protein Therapeutics for Ocular Disease

Purpose To evaluate the stability of a model Mab1 and Fab1 under in vitro vitreal conditions in the presence of various metabolites and in the presence of light at lambda > 400 nM. Methods A full length IgG1 monoclonal antibody (Mab1) and a fab fragment (Fab1) were formulated with various metabolites typically found in the vitreous humor and subjected to visible light treatment. Both proteins were analyzed using a variety of biochemical techniques. Furthermore, Fab1 was also tested for antigen binding ability using surface plasmon resonance. Results Our data shows that some vitreal metabolites such as riboflavin and ascorbic acid affect protein stability, via formation of reactive oxygen species (ROS) and advanced glycation end products (AGE) s respectively. In contrast, metabolites such as glutathione may protect these proteins from light-induced degradation to some extent. Conclusions Ascorbic acid and riboflavin were found to photosensitize therapeutic proteins especially when exposed to light. Ascorbic acid reacted with proteins even in the absence of light. Antioxidants such as glutathione helped limit photooxidation under ambient or blue light exposure. Since antioxidant capacity in the eye decreases with age we recommend understanding long term stability, including photooxidation and photosensitization, of new candidate proteins in the context of controlled or sustained release technologies for ocular diseases.