Developing the therapeutic potential of intrathecal administration strategies through protein PEGylation and microparticle encapsulation and release of pDNA.

摘要

There is a pressing need to improve drug delivery to the brain and spinal cord for the treatment of central nervous system disorders, as formidable obstacles that impede central nervous system delivery limit the clinical relevance of many potential treatments. Direct drug administration to the cerebrospinal fluid (intrathecal administration) is often required to overcome delivery limitations for promising therapies. While intrathecal administration overcomes some delivery obstacles, rapid drug degradation and clearance still necessitate the development of approaches that prolong drug efficacy. Therapeutic treatments utilizing proteins and plasmid DNA (pDNA) are particularly limited by inadequate intrathecal delivery technology. In this thesis, short-term intrathecal protein treatment paradigms were improved by covalently attaching polyethylene glycol (PEG) to brain derived neurotrophic factor (BDNF) and interleukin-10 (IL-10) in a manner that enabled high in vitro biological activity retention. In animal models PEGylation increased resultant protein concentrations in the cerebrospinal fluid over time, and PEGylating IL-10 enhanced its in vivo therapeutic efficacy for the resolution of neuropathic pain by nearly threefold. To overcome prior obstacles with long-term intrathecal treatment strategies for enhanced pain states, biodegradable microparticles containing pDNA for IL-10 were developed. These microparticles resulted in a sustained in vitro release of pDNA and enabled single administration therapeutic efficacy for the long-term resolution of neuropathic pain. Further in vivo explorations with confocal microscopy and fluorescently labeled microparticles demonstrated that microparticles embedded within the tissue surrounding the spinal cord and persisted for prolonged time periods. Microparticle administrations also promoted the infiltration of phagocytic cell types into the cerebrospinal fluid for a prolonged expression of therapeutic pDNA. Overall, these studies demonstrate that polymer-mediated delivery strategies that enhance protein concentrations over time and sustain pDNA release can reduce dosages, minimize intervention requirements and significantly enhance the therapeutic potential of both short- and long-term intrathecal treatment approaches.