Dapivirine, an anti-retroviral (ARV)-based microbicide, is a substituted diaminopyrimidine (DAPY) derivative and a potent non-nucleoside reverse-transcriptase inhibitor (NNRTI) with antiviral activity against HIV-1. Dapivirine showed high activity against wild-type and mutant HIV in in virto HIV models inhibiting a broad panel of HIV-1 isolates from different classes, including a wide range of NNRTI-resistant isolates. Developed by Janssen Sciences (formerly Tibotec Pharmaceuticals), dapivirine was initially tested as an oral treatment for HIV in a number of Phase I/II clinical trials. In 2014 the International Partnership for Microbicides (IPM) began its work on the monthly dapivirine ring. Phase I/II clinical trials in Africa, Europe and the United States proved that dapivirine is safe and well-tolerated. Phase III long-term safety and efficacy studies of the monthly dapivirine ring as part of IPM's Dapivirine Ring Licensure Program confirmed that the monthly dapivirine ring can safely help prevent HIV infection in women. In 2016 the ASPIRE Study reported a 27 percent reduction in HIV-1 acquisition with a trend toward greater protection in women over age 21 and no significant protection for women under age 21.