Methods: Resistance analyses were performed by conventional DNA sequencing of the UL97 gene at multiple time points. Following CMV DNA extraction from frozen whole blood specimens, the UL97 gene was amplified with a double nested polymerase chain reaction method and sequenced to identify polymorphisms and mutations that might confer GCV resistance.
Results: Forty-six infants with symptomatic CMV disease who received a 6-month course of VGCV underwent resistance analysis to identify UL97 sequence variants. In addition to a range of natural polymorphisms known to have no effect on antiviral susceptibility, 2 subjects developed UL97 mutations known to confer resistance to GCV (A594V and G598S detected in one subject; E596G detected in another), yielding an incidence of 4%. Each of these resistance mutations occurred in specimens collected after at least 4 months of antiviral therapy. As evaluated in the original Phase 3 trial, neither of these infants showed an improvement in hearing outcome.
Conclusion: The development of treatment-emergent UL97 resistance mutations was determined in a controlled study population of infants with congenital CMV disease receiving 6 months of VGCV. This targeted resistance analysis demonstrated an incidence approaching the total incidence of antiviral resistance for CMV disease in some immunocompromised populations, such as solid-organ transplant recipients. Further studies within this study population are warranted to elucidate the risk of emerging antiviral resistance and to assess clinical impact as well as the potential need for combination antiviral therapy.
S. H. James,
D. W. Kimberlin, None
R. Whitley, None
M. N. Prichard, None