The evolving design and methods for trials evaluating the safety of candidate vaginal microbicides: a systematic review

Vaginal preexposure prophylaxis is a promising biomedical tool for HIV prevention. Although guidelines for the clinical assessment of microbicides are available, validated markers for product safety are lacking. To inform future microbicide and multipurpose vaginal product research, we reviewed the current and past safety methods used. We searched the Cochrane, EMBASE, and Ovid MEDLINE databases for clinical studies of vaginal products for the prevention of HIV that included safety evaluations. Ninety-seven clinical studies involving 21 products were identified: 63 lasted 14 days or less, 19 were longer in duration, and 15 were effectivess studies that included also safety as an outcome. Median sample size in the safety studies was 48 participants (range, 10-799). All studies reported on urogenital endpoint, 71% included colposcopy, and 67% assessed the vaginal microflora. Markers of vaginal epithelial inflammation, systemic absorption, and systemic toxicology assessments were evaluated in 29%, 26%, and 43% of studies, respectively. Excluding the effectiveness studies, these same assessments were done before 1998 in 33%, 7%, and 27% and after 2001 in 38%, 44%, and 60% of studies, respectively. Soluble inflammatory markers were introduced after 2001. Adverse event collection was reported in 73% of studies before 1998 and in 98% after 2001. In a previous review, we recommended that larger and longer safety studies were necessary to detect clinically important toxicities and to provide assurance that agents are ready for large-scale effectiveness trials. Here, we propose a stepwise clinical assessment that can be used for future guidance.