In vitro evaluation of viability, integrity and inflammation in genital epithelia upon exposure to pharmaceutical excipients and candidate microbicides

Microbicides are a promising approach for the prevention of HIV-1 transmission. Unfortunately, various candidates failed in clinical trials. In some cases, the candidate microbicide even resulted in enhanced virus transmission. Therefore, there is an urgent need to develop more predictive preclinical strategies to anticipate the in vivo efficiency/toxicity rate, including in vitro assays that evaluate effects on epithelial integrity and inflammation. The present study aims to identify potential safety issues concerning the use of microbicides and excipients commonly used in vaginal microbicide preparations. The toxicity of various active pharmaceutical ingredients (APIs) (TMC120, UC-781, PMPA, PRO2000 and GML) and excipients (preservatives, cosolvents, surfactants and cyclodextrins) was evaluated using an in vitro dual-chamber model and uterine cervical explants. Epithelial viability and permeability for fluorescent virus-sized beads, as well as induction of interleukin-8 (as a sensitive marker of an inflammatory response) were assessed. Surprisingly, cell viability and epithelial layer integrity were compromised by most excipients at concentrations near the typical concentration used in vaginal gels and a significant increase in the production of IL-8 was observed at sub-toxic concentrations. Within the API, TMC120, UC-781, PMPA showed a higher selectivity index compared to PRO2000 and GML. In conclusion, identification of safety issues concerning the use of pharmaceutical excipients could help to formulate less toxic vaginal microbicide preparations