title: Preformulation and stability in biological fluids of the retrocyclin RC-101, a potential anti-HIV topical microbicide.
abstract: BACKGROUND
  RC-101, a cationic peptide retrocyclin analog, has in vitro activity against HIV-1. Peptide drugs are commonly prone to conformational changes, oxidation and hydrolysis when exposed to excipients in a formulation or biological fluids in the body, this can affect product efficacy. We aimed to investigate RC-101 stability under several conditions including the presence of human vaginal fluids (HVF), enabling the efficient design of a safe and effective microbicide product. Stability studies (temperature, pH, and oxidation) were performed by HPLC, Circular Dichroism, and Mass Spectrometry (LC-MS/MS). Additionally, the effect of HVF on formulated RC-101 was evaluated with fluids collected from healthy volunteers, or from subjects with bacterial vaginosis (BV). RC-101 was monitored by LC-MS/MS for up to 72 h.
  
  
  RESULTS
  RC-101 was stable at pH 3, 4, and 7, at 25 and 37°C. High concentrations of hydrogen peroxide resulted in less than 10% RC-101 reduction over 24 h. RC-101 was detected 48 h after incubation with normal HVF; however, not following incubation with HVF from BV subjects.
  
  
  CONCLUSIONS
  Our results emphasize the importance of preformulation evaluations and highlight the impact of HVF on microbicide product stability and efficacy. RC-101 was stable in normal HVF for at least 48 h, indicating that it is a promising candidate for microbicide product development. However, RC-101 stability appears compromised in individuals with BV, requiring more advanced formulation strategies for stabilization in this environment.
authors.affiliation: Magee-Womens Research Institute, 204 Craft Avenue, Pittsburgh, PA, 15213, USA. rohanlc@upmc.edu.
authors.forename: Alexandra B
authors.initials: AB
authors.lastname: Sassi
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Bunge
authors.forename: Brian L
authors.initials: BL
authors.lastname: Hood
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Conrads
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Cole
authors.forename: Phalguni
authors.initials: P
authors.lastname: Gupta
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Rohan