Maraviroc is being considered for a patient with multidrug-resistant HIV. Before prescribing, which investigation is mandatory?

• A A viral tropism assay confirming the circulating virus uses CCR5 rather than CXCR4 ✓
• B Measurement of baseline serum CCR5 receptor density on CD4 cells
• C Genotypic testing for mutations in the HIV envelope gp41 protein
• D Quantitative HIV DNA PCR to exclude proviral latency

Explanation

Maraviroc blocks the CCR5 coreceptor and therefore works only if the patient's dominant viral population is CCR5-tropic. B tropism assay is mandatory before starting, because CXCR4-tropic or dual-tropic virus renders the drug ineffective, and treatment pressure can select for CXCR4 variants during therapy. Gp41 genotyping relates to enfuvirtide resistance, and receptor density on host cells does not determine susceptibility since the viral envelope determines coreceptor usage.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.