Comparative Study of In Situ Loaded Antibody and PEG‐Fab NIPAAM Gels

Abstract

Hydrogels can potentially prolong the release of a therapeutic protein, especially to treat blinding conditions. One challenge is to ensure that the protein and hydrogel are intimately mixed by better protein entanglement within the hydrogel. N-isopropylacrylamide (NIPAAM) gels are optimized with poly(ethylene glycol) diacrylate (PEDGA) crosslinker in the presence of either bevacizumab or PEG conjugated ranibizumab (PEG -Fab ). The release profiles of the hydrogels are evaluated using an outflow model of the eye, which is previously validated for human clearance of proteins. Release kinetics of in situ loaded bevacizumab-NIPAAM gels displays a prolonged bimodal release profile in phosphate buffered saline compared to bevacizumab loaded into a preformed NIPAAM gel. Bevacizumab release in simulated vitreous from in situ loaded gels is similar to bevacizumab control indicating that diffusion through the vitreous rather than from the gel is rate limiting. Ranibizumab is site-specifically PEGylated by disulfide rebridging conjugation. Prolonged and continuous release is observed with the in situ loaded PEG -Fab -NIPAAM gels compared to PEG -Fab injection (control). Compared to an unmodified protein, there is better mixing due to PEG entanglement and compatibility of PEG -Fab within the NIPAAM-PEDGA hydrogel. These encouraging results suggest that the extended release of PEGylated proteins in the vitreous can be achieved using injectable hydrogels.

Antibody loaded collapsible hyaluronic acid hydrogels for intraocular delivery

“…In a previous study conducted in our laboratory, LCST values ranged from 34.3 ± 0.2 to 36.2 ± 0.2°C (p<0.05) for PEGDA amounts from 2-6% (with pNIPAAM-PEGDA hydrogels). 32 Isopropyl groups predominate above the LCST leading to an aggregation mechanism that results in the overall domination of hydrophobicity. 46 The polymer chain retracts from the surrounding solvent in a repulsive force manner.…”

“…The use of a collapsible thermoresponsive hydrogel provides the potential for further prolongation of antibody release from an injected hydrogel formulation. Poly(Nisopropylacrylamide) (pNIPAAM) is a thermoresponsive polymer [26][27][28][29][30][31][32][33] that is biocompatible, but it is not biodegradable. 34 Incorporation of a HA biodegradable component 35,36 as an IPN in the pNIPAAM network is one strategy to allow the clearance of pNIPAAM.…”

Injectables and Depots to Prolong Drug Action of Proteins and Peptides

“…They are also useful for circumventing the need for frequent repeat injections—which presents several risks and complications to patients—by acting as a drug depot even for unstable protein molecules [ 140 ]. There are a number of in-situ gelling systems reported for ocular delivery of proteins [ 225 , 300 , 301 , 302 , 303 , 304 , 305 , 306 , 307 , 308 ]. Xue et al [ 305 ] developed thermosensitive gels of anti-VEGF drugs (bevacizumab and aflibercept) using a PEG-polypropylene glycol (PPG)-PCL multiblock copolymer (hydrophilic–hydrophobic biodegradable copolymer) [ 305 ].…”

“…To design an efficient in-situ gelling system, it is vital that the rate of reaction be rapid enough to encapsulate the protein and prevent the removal of gelling precursors, but sufficiently slow to allow the injection of the pre-gel solution [ 271 ]. Awwad and co-workers [ 225 , 300 , 308 ] have reported the in vitro delivery of antibodies with thermoresponsive hydrogels. These authors [ 308 ] reported the sustained release (over 30 days) of bevacizumab and PEG-conjugated ranibizumab (PEG-Fab rani ) from a crosslinked N -isopropylacrylamide (NIPAAM) hydrogel [ 308 ].…”

“…Awwad and co-workers [ 225 , 300 , 308 ] have reported the in vitro delivery of antibodies with thermoresponsive hydrogels. These authors [ 308 ] reported the sustained release (over 30 days) of bevacizumab and PEG-conjugated ranibizumab (PEG-Fab rani ) from a crosslinked N -isopropylacrylamide (NIPAAM) hydrogel [ 308 ]. In another study [ 300 ], bevacizumab was released for at least 2 months from a biodegradable NIPAAM-acrylated HA (Ac-HA) hydrogel [ 300 ].…”