(M1330-01-03) Engineering Extended-Release Profiles for Biologic Drugs via Chemical Crosslinking of Poloxamer 407 Hydrogels

Purpose: Biologic drugs, including peptides, proteins, and antibodies, often require high and frequent dosing due to their larger molecular sizes and sensitive nature. This can lead to undesirable side effects, patient discomfort, and increased treatment costs. To improve the efficacy of biologic drugs and enable administration through various routes, encapsulating them in polymeric hydrogel formulations can enhance stability and modulate release profiles. In particular, Poloxamer 407 (P407) is a unique polymer that remains liquid at ambient temperature but transitions to gel at physiological temperature, rendering them ideal for hydrogel formulations for biologics delivery. However, its low mechanical strength and rapid disintegration in aqueous media within 1-2 days have limited its therapeutic applications. To address these limitations, we developed crosslinked P407 hydrogels using acrylate-modified P407 and thiol-terminated eight-arm polyethylene glycol (PEG) with varying molecular weights to achieve extended release of proteins and antibodies. The combination of thermal gelation and covalent crosslinking resulted in stable hydrogels capable of in situ formation, demonstrating significant potential for sustained and controlled release of biologics.

Methods: Hydrogel formulations were prepared by mixing concentrated solutions of acrylate-modified P407, which undergo temperature-induced sol-gel transitions, with thiolated eight-arm PEG polymers for subsequent crosslinking. Aqueous solutions of acrylate-modified P407 were prepared in phosphate buffer at a 25% (w/v) concentration, and subsequently mixed with 5% (w/v) and 10% (w/v) for 10 kDa and 20kDa thiolated eight-arm PEG, respectively, to allow for secondary covalent crosslinking. The thermal gelation of these formulations was assessed using a glass vial inverting method and oscillatory rheology. In vitro release profiles of model biomacromolecules, including bovine serum albumin (BSA) and antibodies, were evaluated at 37 °C. The stability and integrity of the encapsulated proteins were confirmed through a range of biophysical characterization techniques.

Results: Crosslinked P407 hydrogels were developed using acrylate-modified P407 and thiol-terminated eight-arm PEG through Michael-type addition. This crosslinking significantly enhanced the mechanical strength of the hydrogels by 2.0-fold compared to non-crosslinked P407, as determined by oscillatory rheology measurements. This improvement allowed for extended in vitro release of BSA, human plasma immunoglobulin G (IgG) antibody, and adalimumab for up to 70 days with tunable release kinetics, while non-crosslinked P407 hydrogels achieved full release within 24 hours. Biophysical characterization of the released biologics using size exclusion chromatography (SEC), capillary electrophoresis sodium dodecyl sulfate (CE-SDS), circular dichroism (CD), and enzyme-linked immunosorbent assay (ELISA) confirmed that the hydrogels did not adversely affect the structural integrity, stability, or in vitro potency of the encapsulated biologics.

Conclusion: This study highlights the impact of crosslinking on the mechanical properties and release kinetics of the P407 hydrogel system. Through crosslinking, P407 hydrogel’s stability was markedly enhanced, enabling it to achieve an extended-release profile with tunable release kinetics by incorporating acrylate-reactive PEG crosslinkers with varying molecular weights. These injectable, thermo responsive hydrogel formulations offer a promising approach for the controlled and sustained delivery of biomacromolecules, providing significant potential for developing long-acting injectable formulations of biologic therapeutics designed for sustained and controlled release, ultimately improving patient comfort, convenience, and compliance.