A 30-year-old HIV-positive patient with CCR5-tropic virus is prescribed maraviroc. What is the mechanism of action of maraviroc?

• A Inhibitor of HIV integrase, preventing proviral DNA insertion
• B Fusion inhibitor binding gp41 to prevent viral-cell membrane fusion
• C Post-attachment inhibitor binding CD4 to prevent co-receptor engagement
• D Competitive antagonist at the CCR5 co-receptor, blocking HIV entry ✓

Explanation

Maraviroc is a CCR5 co-receptor antagonist that allosterically binds CCR5, preventing the HIV gp120-CCR5 interaction required for entry. It is active only against R5-tropic virus; tropism testing is mandatory before use. Enfuvirtide binds gp41. Ibalizumab is the CD4-directed post-attachment inhibitor. Raltegravir inhibits integrase.

Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.

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