BIOPHARMACEUTICAL MICROBICIDES FOR TOPICAL HIV PREVENTION:PRE-CLINICAL EVALUATIONS AND FORMULATION DEVELOPMENT

Over 60 million people have been infected with HIV since the beginning of the epidemic. Currently available methods for prevention have not been sufficient to stop the progression of this pandemic. Considering that many women are unable to negotiate condom use with their partners and are more susceptible to HIV, strategies to prevent heterosexual transmission of HIV must include female-controlled methods. A promising strategy is the development of a topical microbicide to prophylactically inhibit transmission of sexually transmitted infections, including HIV.The work presented makes significant contributions to the microbicide research field, focusing on product development, preformulation strategies, stability in biological fluids, and drug targeting. We investigated two biomolecule (protein/peptide) microbicide candidates: PSC-RANTES, a chemokine analog of RANTES; and RC-101, a circular theta-defensin analog. We hypothesized that the use of a drug delivery system will protect the microbicide candidate against degradation before administration, and in biological fluids after administration, while maintaining drug activity. Further, the interaction of the microbicide candidates with human vaginal fluids can result in chemical modification of the drug.Identification of degradation pathways for PSC-RANTES and RC-101 was conducted by performing preformulation studies under selected conditions of temperature, pH, and oxidative conditions. Analytical methods used included HPLC, MALDI-TOF MS, CD, and SDS-PAGE. Chemical modifications of RC-101 were evaluated in the presence of human vaginal fluid collected from healthy female volunteers and detected by LC-MS/MS. RC-101 was formulated in a quick-dissolving vaginal film and showed short term stability, efficacy in vitro and safety in vivo in an animal model. Tissue localization of RC-101 was evaluated using excised human (ectocervical and endometrium) and monkey (vaginal and endometrium) tissues. Major findings from this work show that: RC-101 formulated in a film drug delivery system protected the peptide from degradation prior to administration; anti-HIV activity of RC-101 was maintained in the formulation; RC-101 was stable at least for 48 h in the presence of human vaginal fluid; and penetration of RC-101 into epithelial tissue was demonstrated. These results contribute to the development of RC-101 into a successful microbicide product and provide a systematic tool for the development of other microbicide molecules