- Triple-class antiretroviral treatment, as determined by the site investigator and as defined by all of the following: a) exposure to 2 or more nucleotide reverse transcriptase inhibitors (NRTIs) for at least 3 months each; b) exposure to 2 or more non-boosted protease inhibitors (PIs) for at least 3 months each, or exposure to a dual PI regimen for at least 3 months; and c) exposure to at least 1 non-nucleotide reverse transcriptase inhibitor (NNRTI) for at least 3 months.