Name four major classes of ART and provide a representative drug from each.

• A. NRTIs emtricitabine; NNRTIs efavirenz; Protease inhibitors darunavir; Integrase inhibitors dolutegravir
• B. NRTIs zidovudine; NNRTIs efavirenz; Protease inhibitors ritonavir; Integrase inhibitors maraviroc
• C. NRTIs lamivudine; NNRTIs etravirine; Protease inhibitors indinavir; Integrase inhibitors enfuvirtide
• D. NRTIs abacavir; NNRTIs nevirapine; Protease inhibitors saquinavir; Integrase inhibitors ritonavir

Answer: (A)

Four major ART classes are NRTIs, NNRTIs, protease inhibitors, and integrase strand transfer inhibitors. Emtricitabine is a classic NRTI: it’s a nucleoside analog that gets phosphorylated inside the cell and competes with natural nucleotides, causing DNA chain termination when incorporated. Efavirenz represents the NNRTIs: it binds to reverse transcriptase at a site away from the active center and induces a conformational change that blocks enzyme activity. Darunavir is a protease inhibitor: it blocks the HIV protease enzyme, preventing the cleavage of viral polyproteins and producing noninfectious, immature virions. Dolutegravir is an integrase inhibitor: it inhibits the viral integrase enzyme, stopping integration of viral DNA into the host genome and halting replication.

The other options mix drugs that don’t consistently represent four distinct classes. For example, some choices include a CCR5 antagonist or a fusion inhibitor or use boosters in place of a true integrase inhibitor, so they don’t illustrate one drug from each of the four major classes. The combination with emtricitabine, efavirenz, darunavir, and dolutegravir cleanly covers all four classes with representative drugs.