Tivirapine, also known as R-86183, is a HIV-1 specific reverse transcriptase inhibitor. It inhibits the replication of HIV-1, but not HIV-2, in a variety of CD4+ T-cell lines and peripheral blood lymphocytes. Whereas an HIV-1 strain containing the Leu-100-->Ile mutation in the RT gene is about 400-fold less susceptible, R86183 still inhibits the replication of an HIV-1 strain containing the Tyr-181-->Cys RT mutation by 50% at a concentration of 130 nM. Tivirapine had been in phase I clinical trial for the treatment of HIV-1 infection. However, this development was discontinued.