Release and activity of anti-TNFα therapeutics from injectable chitosan preparations for local drug delivery

Background: Tumor necrosis factor alpha (TNFα) is a cytokine that regulates immune and inflammatory overactivation in various pathological states. Protein therapeutics may antagonize this cytokine, but may also have systemic toxicities. Small molecule natural products are also efficacious, but can suffer from poor oral bioavailability. A drug delivery vehicle is needed to sustain release of active therapeutics and address localized inflammation. Materials: Chitosan is a biocompatible aminopolysaccharide that undergoes thermallyinitiated gelation in cosolutions with glycerophosphate (GP), and may entrap and sustain release of additive therapeutics. Gelation time and temperature of chitosan/GP were evaluated by turbidity (OD350), as was the kinetic effect of bovine serum albumin (BSA) entrapment. We investigated in vitro release of BSA and various anti-TNF agents (curcumin, sTNFRII, anti-TNF antibody) and confirmed in vitro activity of the released drugs using an established bioassay. Results: Turbidity results show that chitosan/GP thermogel achieves gelation at 37°C within 10 min, even with significant protein loading. Sustained BSA release occurred with 50% retained at 7 days. All anti-TNF therapeutics exhibited sustained release, with 10% of sTNFRII and anti-TNF antibody remaining after 7 days and 10% of curcumin remaining after 20 days. After release, each compound antagonized TNFα-cytotoxicity in murine fibrosarcoma cells. Conclusions: This study demonstrates that thermogelling chitosan/GP entraps and sustains release of a broad range of anti-TNF agents. Such delivery of disease-modifying therapy could establish a drug depot to treat local inflammation. The breadth of molecular sizes demonstrates significant versatility, and slow release could protect against toxicities of systemic delivery.