What was the target in the drug design that created Ritonavir?

• A. Cytochrome P450 enzyme.
• B. Bacterial cell wall synthesis.
• C. Monoamine oxidase.
• D. Human immunodeficiency virus protease.

Answer: (D)

Ritonavir was designed to inhibit the HIV protease, the enzyme that cleaves viral polyproteins into mature, functional proteins. By blocking this protease, HIV particles cannot mature properly, so they become noninfectious. Ritonavir acts as a protease inhibitor by mimicking the peptide substrate and binding to the protease’s active site. While it later became well known for strongly inhibiting CYP3A4 (used to boost levels of other drugs), the primary design target for its antiviral action is the HIV protease. The other options don’t fit because they’re not the viral maturation target (bacterial cell wall synthesis, monoamine oxidase) and the design isn’t aimed at a cytochrome P450 enzyme for its intended antiviral effect.