A Composite Polymeric Drug Delivery System for Treatment of Spinal Cord Injury

There are no clinically approved drug delivery strategies designed for localized and sustained release to the injured spinal cord, two features which are heavily exploited in pre-clinical demonstrations of efficacy. We have previously shown that injection of drug loaded hydrogels into the intrathecal space is safe, minimally invasive, and drug release localized to the site of injection for up to one day. In the present work we developed a platform for sustained release from 1 to 28 days based on a physical gel of methylcellulose with hyaluronan and poly(lactic-co-glycolic acid) (PLGA) nanoparticles added as gelation agents. These composite hydrogels met the design criteria of injectability, fast gelation, minimal swelling, and 28 day stability. Sustained release of 6 therapeutic molecules from the composite was achieved by encapsulation in the particles or dissolution in the hydrogel. Release of PLGA encapsulated drugs from the composite was linear for 28 days. Drugs dissolved in the hydrogel were released by Fickian diffusion. The HAMC hydrogel/PLGA nanoparticle composite was delivered to uninjured and spinal cord injured rats and the animals monitored for 14 and 28 days respectively. The composite was well tolerated in the intrathecal space with no impact on motor function as determined by the BBB scale and minimal inflammation in both studies. No increase in reactive astrocytes or cavity volume was found in clip compression spinal cord injured rats, indicating that the composite did not affect these aspects of the secondary injury cascade. We then turned to sustained release of anti-NogoA, a promising neuroregenerative molecule typically delivered for 2 - 4 weeks. Formulations of anti-NogoA or a model IgG were prepared and release was demonstrated over 28 days in vitro. Bioactivity was assessed using a novel ELISA which utilized anti-NogoA / NogoA binding to detect only active antibody, advantageous because anti-NogoA release can now be easily optimized prior to in vivo studies of efficacy. The key features of current work are the development of an intrathecal drug delivery platform, demonstration of safety in a rat model, and formulation for use with anti-NogoA.Ph