Extended release aflibercept with sustained vitreous concentration in non-human primates from biodegradable hydrogel implants

Abstract

Purpose : Decreasing the frequency of intravitreal injections of standard anti-VEGF therapies by means of extended release formulations would not only result in reduced burden to patients but may also result in improved clinical outcomes in the treatment of posterior angiogenesis. We demonstrate the ability to formulate extended release intravitreal implants by encapsulating solid state micronized protein in biodegradable hydrogel matrices. Protein release can be tuned to desired release rate and recent formulation optimization shows increased protein stability in vitro

Methods : In vitro release rate and monomer content of released aflibercept were monitored in 1X PBS pH 7.4 at 37 degrees^oC using total protein assays, VEGF ELISA, and size exclusion chromatography. Formulations were screened for protein stability using accelerated degradation conditions (40^oC/75% Relative Humidity). African Green monkeys received either a bolus injection of Eylea® (n=4 eyes) or ENV1305 extended release aflibercept implants (n=8 eye) by bilateral intravitreal injection, and were followed for up to 3 months. Vitreous humor was assayed for aflibercept using an ELISA assay.

Results : Addition of excipients to the protein formulations reduced aggregation of aflibercept under accelerated degradation conditions resulting in increased stability of protein released from hydrogel formulations in vitro. In vitro release studies demonstrate complete release of protein over several months at therapeutically relevant levels and physicochemical characterization indicates that the released protein is comparable to initial starting material with respect to VEGF binding (ELISA) and monomer content (SEC). ENV1305 extended release implants demonstrated sustained vitreous concentrations out to 3 months in African Green Monkeys at relevant levels compared to Eylea.

Conclusions : We demonstrate the ability to formulate biodegradable intravitreal implants with tunable, reproducible release kinetics of anti-VEGF biologics. Optimization based on accelerated degradation led to formulations that release stable protein over the duration of the implant. Our in vitro data establishes proof of concept for multi-month extended release of active anti-VEGF biologics, and supporting data collected in primates demonstrates the potential for therapeutically-relevant aflibercept release in vivo for up to 3 months.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.