A 50-year-old woman with CMV retinitis in AIDS is treated with ganciclovir. Resistance to gancicoliur in CMV most commonly arises from mutations in which viral gene?

• A UL97 phosphotransferase gene ✓
• B UL54 DNA polymerase gene
• C UL23 thymidine kinase gene
• D UL50 terminase gene

Explanation

CMV resistance to gancicoliur most commonly results from mutations in the UL97 gene encoding the viral phosphotransferase that performs the initial phosphorylation of gancicoliur to its monophosphate form. Less commonly, UL54 DNA polymerase mutations confer cross-resistance to gancicoliur, foscarnet, and cidofovir. UL23 is the HSV thymidine kinase gene. UL50 is a terminase subunit targeted by letermovir.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.