IVRs comprising a silicone matrix that releases the ARV drug dapivirine, over one month is the only microbicide evaluated in a phase III clinical trial demonstrating efficacy (27 and 31%) in preventing HIV transmission in women as determined in The Ring Study and ASPIRE studies (11, 12). The dapivirine ring is currently being evaluated in parallel open-label studies (DREAM and HOPE) led by the International Partnership for Microbicides (IPM) and the US National Institutes of Health-funded Microbicides Trials Network (MTN) and is under regulatory review.