LYOPHILIZATION OF NONVIRAL GENE DELIVERY SYSTEMS

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More efficient synthetic gene delivery systems continue to be developed and tested in human clinical trials. While much progress has been made in improving non-viral vectors, some critical pharmaceutical problems remain unresolved. For example, the tendency of non-viral vectors to aggregate limits the potential for widespread use of this technology. This instability introduces variability in product quality and does not allow preparations to be extensively tested prior to use. As a result, there is tremendous interest in developing stable lyophilized formulations that could be shipped and stored at ambient temperatures. Preliminary studies have clearly demonstrated that the freeze-drying process significantly alters physical characteristics and reduces biological activity of non-viral vectors. Utilizing an empirical approach, these studies have also shown that disaccharides are capable of protecting synthetic delivery vehicles during acute lyophilization stress, but have yet to address the mechanism of stabilization or preservation during storage. Previous work with liposomes and proteins has suggested two competing mechanisms to explain protection provided by sugars. However, it is unclear whether either of these mechanisms is applicable to the stabilization of non-viral vectors. The work described in this proposal will test whether the mechanisms employed by excipients to stabilize other biopharmaceuticals in the dried state are applicable to macromolecular complexes used in gene delivery. Recognizing that many different types of non-viral vectors are being optimized for gene therapy, the primary goal of our study is to develop rational formulation guidelines that are generally applicable to the stabilization of DNA-based macromolecular complexes during freeze- drying and storage. In addition to designing excipient formulations to stabilize lyophilized preparations, these studies will help to better characterize the "native state" of synthetic gene delivery systems.