In Vitro Evaluation of Viability, Integrity, and Inflammation in Genital Epithelia upon Exposure to Pharmaceutical Excipients and Candidate Microbicides

Abstract

The use of microbicides is 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 toxicities of various active pharmaceutical ingredients (APIs; TMC-120, UC-781, tenofovir [PMPA], PRO-2000, and glycerol monolaurate [GML]) and excipients (preservatives, cosolvents, surfactants, and cyclodextrins) were evaluated using an in vitro dual-chamber model and uterine cervical explants. Epithelial viability and permeation of fluorescent virus-sized beads, as well as induction of interleukin-8 (IL-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 subtoxic concentrations. Within the APIs, TMC-120, UC-781, and PMPA showed higher selectivity indices than PRO-2000 and GML. In conclusion, identification of safety issues concerning the use of pharmaceutical excipients could help to formulate less toxic vaginal microbicide preparations.

HIV sexual transmission and microbicides

“…Furthermore, according to our own findings on the cytotoxic effects of gel formulations and excipients (i.e. constituents of gels such preservatives, co-solvents, surfactants and cyclodextrins) on female genital epithelium, the gel formulation used in this trial is non-cytotoxic under in vitro conditions [242]. These observations complement the trial findings on tolerability and safety of tenofovir gel.…”

The Effect of Commonly Used Excipients on the Epithelial Integrity of Human Cervicovaginal Tissue

“…8,28,29 Although identified as generally-regarded-as-safe excipients by the Food and Drug Administration (FDA), several of these excipients were reported to affect the epithelial barrier in human cell culture or animal models. [18][19][20][21] Excipients chosen for evaluation represent a variety of functional categories and diverse chemical structures. The excipient concentration used in this study (Table 2) was determined based on the following considerations: Disodium EDTA is widely reported to decrease the integrity of intestinal cell monolayer (Caco-2) 30 and excised intestinal epithelium, 31 so three concentrations (0.05%, 0.1%, and 1%) were chosen to cover the relevant levels of use.…”

“…18 Several other tissue explant and mouse studies reported that treatment with excipients that are frequently used in vaginal products could alter the cervicovaginal tissue integrity and even increase the rate of vaginal herpes simplex virus 2 (HSV-2) transmission. [19][20][21] McClelland et al evaluated the effect of vaginal washing on the incidence of HIV-1 infection in 1,270 African women between 1993 and 2003. They found that women who partake in vaginal washing, by vaginal douching or washing with water and soap, had higher HIV acquisition risk as compared with women who did not perform vaginal washing.…”

Impact of Hydroxychloroquine-Loaded Polyurethane Intravaginal Rings on Lactobacilli

“…As a result, there is an urgent need to develop effective safe microbicides that can prevent HIV-1 infection. Damage to the vaginal epithelial surface due to certain chemicals and drug carriers can cause inflammation of the FGT (21,22), resulting in increased risk of HIV acquisition, as observed in several failed microbicide trials (23,24). Furthermore, the majority of microbicide studies have focused on the ability of the microbicide to induce inflammation in vaginal epithelial and immune cells (25).…”