A Collagen-based Formulation for Sustained Release of Aflibercept

Angiogenesis is a chronic condition in wet- age-related macular degeneration (AMD) disease that is currently considered the leading cause of irreversible blindness in the elderly population. Vascular endothelial growth factor (VEGF) is a pro-angiogenic cytokine which its inhibition has revolutionised treatment of wet-AMD.

Aflibercept is anti-VEGF Fc-fusion protein, which is currently considered as a golden therapy for treatment of AMD and retinal neovascularization. Aflibercept inhibits VEGF from binding to VEGF-receptor and has a binding affinity towards all isoforms of VEGF-A family member. Intravitreal injections of Aflibercept are given every 4 weeks, followed by the regular injection every 8 weeks for several years. The frequency of injection is not convenient for the elderly patient. Hence, there is a recognised need to increase the residence time of aflibercept in the vitreous to decrease the frequency of intravitreal injection.

Different strategies to prolong the vitreous residence time of therapeutic proteins have been suggested, but these must address the challenges to maintain protein stability and ocular tolerability. One strategy is to use collagen drug delivery method to sustain the release of therapeutic protein. We have used In situ polymerized collagen (IPC) to formulate aflibercept with the aim to sustain the release of aflibercept once it’s injected to the vitreous. This could potentially lead to improving patient compliance and enhanced efficacy for drug. The IPC solution could rapidly form a dense fibril structure when exposed to physiological conditions (pH 7.4, 37°C) and physiological fluids such as PBS. Initially, when sink model (no flow) was used, an increase in aflibercept release profile from 1 day to 4-5 days for the IPC formulation was observed. Rig model connected to peristaltic pump to mimic ocular vitreous flow rate (2μL/min) and volume size (200μL), was later used to examine the release profile of collagen-based aflibercept formulation. Optimization of the aflibercept-IPC formulation was performed to extend the release profile with a proper ratio of IPC/Aflibercept and incorporating Hyaluronic acid (HA). Because of the high hydrophilicity properties of HA, cross-link HA provides a high swelling factor to maintain excellent tamponade effect by reducing the initial burst release of drugs.

The aflibercept release from HA-IPC formulation achieved a zero-order kinetics and an extended release of more than 13 days was observed. Other excipients such as polyethylene glycols and surfactants e.g., Tween-20 were also used in the formulation to extend the release of aflibercept from collagen system. Our results, however, showed no significant difference on release profile of aflibercept when PEGs and Tween-20 were used in the formulation. While more studies need to be done to fully characterise the release profile of aflibercept, our preliminary results presented in this MRes, suggest that using HA-based IPC formulation could be a promising delivery method to prolong the action of aflibercept in the vitreous.