Biomarkers are becoming an increasingly valuable approach to both diagnosis and treatment of disease in areas such as cancer and cardiology. They can serve to indicate the presence of a disease process and of response to treatment, and can give indication of genetic susceptibility to both disease and drug effects. However, their use in prevention research has so far been limited and is undeniably challenging.

In the area of vaginal product research, biomarkers could give early information about the safety and likely efficacy of both contraceptive and microbicide products, facilitating triage of less promising candidate products, design of smaller-scale effectiveness trials and, therefore, more efficient use of human and financial resources. If a biomarker of HIV transmission could be found that would give an early indication of the likely efficacy of a candidate microbicide before thousands of women are enrolled in a Phase III trial, the benefit to the microbicide field, and perhaps others, would be great. Because of this critical potential, work on biomarkers and surrogates of safety and efficacy is a priority action called for by the Microbicide Development Strategy produced under the aegis of the Microbicide Donors' Committee with support from the Bill and Melinda Gates Foundation.

CONRAD, in collaboration with Ibis Reproductive Health and NIH, has been spearheading the effort to find a biomarker of semen exposure suitable for use in contraceptive and microbicide efficacy trials. CONRAD and Ibis sponsored a meeting funded in part by NICHD and NIAID entitled "Evaluation of Markers of Intercourse in Trials of Vaginal Barriers," in 2004. There are major gaps in knowledge about these markers and work begun at the meeting has been continued by two sub-groups, one devoted to preclinical aspects of markers and one devoted to clinical aspects. The clinical group has been especially active since January 2005; two studies are already underway as a result of its work, and a manuscript was recently submitted for publication by this group. The preclinical group has compiled a list of potential new biomarkers of semen, and has outlined the initial experiments needed to characterize and validate them.

In addition, CONRAD and the Alliance for Microbicide Development are sponsoring a meeting to be held in November (funded in part by the Bill and Melinda Gates Foundation and the United States Agency for International Development) to review the current status of biomarkers not just of semen exposure but of inflammation and HIV exposure. The meeting will assess how emerging technologies might be applied to the microbicide field, and to encourage innovation and collaboration among a broad spectrum of researchers within and beyond that field.

Abstract: Biomarkers of semen exposure: Applications in Trials of HIV/STI Prevention