In vitro activity: Dapivirine prevents HIV-induced syncytium formation in the nanomolar range and shows a low cytostatic activity. Dapivirine apparently blocks HIV-1 infection in the primary cultures at a 10 nM concentration, but secondary cultures reveals that a 100 nM concentration is needed to completely prevent proviral integration. Dapivirine is well tolerated by epithelial cells, T cells, macrophages, and cervical tissue explants with CC50 (50% cytotoxic concentration) of 10 μM to 20 μM. Dapivirine potently inhibits infection by both X4- and R5-utilizing HIV-1 strains with IC50 of 1.46 nM in cell-based assays. Dapivirine potently inhibits HIV-1BaL infection of human ectocervical explant tissue in a dose-dependent manner, as evaluated by the reduction in both p24 release and provirus content in cultured explants. Dapivirine inhibits the transmission of virus to permissive T cells in a dose-dependent manner, with an IC50 of 0.1 nM. Dapivirine results in significant inhibition of HIV infection when explants are challenged with virus immediately with IC90 of 100 nM. Dapivirine is also able to inhibit viral dissemination by migratory cells.

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