Technologies for Reproductive Health

Potential of the SILCS Diaphragm as a multipurpose prevention technology

Clinical data confirm that the SILCS Diaphragm provides similar contraceptive protection as a traditional multisize diaphragm when used with a contraceptive gel. Further innovation could expand the benefits of SILCS to offer protection against sexually transmitted infections (STIs), including HIV, by combining its use with a microbicide.

Multipurpose prevention technologies (MPTs) are drugs or devices that simultaneously prevent unintended pregnancy; HIV; and/or other STIs, such as HPV (human papillomavirus), HSV (herpes), syphilis, chlamydia, and others. Currently, options for multipurpose prevention are limited to the male and female condom, but these methods do not meet the needs of every person, in every country, and in every situation. The potential for SILCS combined with a microbicide as a multipurpose prevention method is promising.

To increase the potential health impact, PATH and other researchers are exploring SILCS used with a microbicide to prevent transmission of HIV and STIs in addition to its contraceptive protection properties. Microbicides are gels, films, or suppositories that can kill or neutralize viruses and bacteria. At present, an effective microbicide is not available; however, there are promising candidates such as tenofovir (TFV) gel that have been evaluated in clinical studies.

SILCS as a microbicide gel delivery system

One approach for SILCS as an MPT is to use SILCS as a reusable delivery system for microbicide gels. The microbicide is applied to the diaphragm before insertion, similar to how contraceptive gel is applied. PATH has implemented two preliminary studies in the United States that assess feasibility and acceptability of SILCS as a microbicide gel delivery system compared to gel delivered from a vaginal applicator. Based on the results from these studies, CONRAD is planning two clinical studies to assess the barrier effectiveness of SILCS when used with TFV gel and the safety and effectiveness of drug delivery.

If using SILCS as a reusable delivery system for microbicide gel is effective and acceptable, it could offer several advantages over gel delivered by a vaginal applicator. The diaphragm holds the gel high in the vagina near the cervix, which could reduce messiness and leakage. In addition, since the diaphragm is a contraceptive method, combining the two products could reduce the stigma associated with the use of a product to protect against HIV. Since the diaphragm is reusable for up to two years, this could reduce the cost and the environmental impact of microbicide gel delivery.

SILCS as a slow-release microbicide delivery system

The second approach for SILCS as an MPT is to load an antiretroviral drug into the SILCS spring during the production process. This allows controlled release of the drug over time when the woman wears the diaphragm. PATH and researchers at Queens University Belfast (Queen’s) recently completed “proof of concept” bench testing of these prototype devices. Queen’s successfully manufactured SILCS to contain dapivirine, an antiretroviral drug being developed as a vaginal microbicide by the International Partnership for Microbicides. In vitro release of dapivirine at a constant rate is extended over a period of at least 12 months, illustrating the potential of this new device.

The next step needed to assess the feasibility of this design concept involves safety and efficacy testing in animals. During a recent review of MPT products in the PATH development pipeline, this technology did not make the list for additional funding. PATH and its partners will continue to seek opportunities for funding in the future as priorities evolve.

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