Evaluation of protein drug performance with vitreous humor in a novel ex-vivo intraocular model

摘要

Purpose: The stability of protein therapeutics during the residence time in the vitreous humor (VH) is an important consideration for intraocular treatment and can possibly impact therapeutic efficacy and treatment intervals. Not much attention has been paid to investigate the physical and chemical stability of therapeutic protein with VH components following intravitreal (IVT) delivery. It may be due to the unavailability of a reliable and representative in-vitro model for in-vivo conditions. Therefore in current study, we have developed and accessed a novel non-cell based Ex-vivo intravitreal (ExVit) model to study stability of proteins in simulated intraocular conditions. The ExVit model facilitated incubation of model proteins for desired period of time in simulated in-vivo conditions enabling the possibility to study protein-VH interactions. We have investigated various stability parameters such as levels of soluble and insoluble aggregates, amount of degradation products, and changes in the pH and osmolality at different time intervals. Methods: We have developed and evaluated three Ex-vivo intravitreal (ExVit) models, namely, ExVit static, semi-dynamic and dynamic. These models were utilized and compared when studying the in-vitro stability of model protein formulations under simulated intraocular conditions using porcine vitreous humor (VH). Samples were analyzed for turbidity, pH, aggregation, degradation products, osmolality and protein content. Results: The static model showed significant pH change likely due to degradation of the VH, making it an unsuitable model to investigate protein stability. The changes observed with added MAb are likely due to the impact of higher pH and/or VH degradation products. The ExVit semi-dynamic model effectively reduced/cleared the decomposition products of VH and maintained pH, however, it was unable to modulate diffusion rates. This restraint eventually limited its applicability to investigate long-term stability of proteins and their formulation following IVT injection. The ExVit dynamic model can be considered an advanced model which provides an opportunity to modulate the rate of diffusion, and Papp. Conclusions: The ExVit models have high potential to investigate the stability of proteins following intraocular injection and hence, choice of the right model is critical.