Mozenavir is a non-peptidomimetic, water soluble, cyclic urea that is a selective inhibitor of HIV-1 protease. Mozenavir is active against the virus with the signature D30N nelfinavir resistance-associated mutation and the L90M mutants with decreased susceptibility to a number of other protease inhibitors. In a dose-ranging study assessing Mozenavir, in doses of 750 mg 3 times a day, 1250 mg twice daily, or 1250 mg 3 times a day, compared with standard doses of indinavir, both in combination with lamivudine and stavudine, plasma HIV-1 RNA levels were reduced to below 50 copies/mL in 75% to 80% of patients receiving Mozenavir-based treatment and in 70% of those receiving indinavir-based treatment. Mozenavir-based regimens were generally well tolerated. However, the virus was able to mount considerable resistance against this compound, which was not further developed, also because of poor oral bioavailability in humans and highly variable blood levels.