Phenotype and Genotype Study of Novel C480F Maribavir-Ganciclovir Cross-Resistance Mutation Detected in Hematopoietic Stem Cell and Solid Organ Transplant Recipients

Two transplant recipients (1 kidney and 1 hematopoietic stem cell) received maribavir (MBV) after cytomegalovirus (CMV) infection clinically resistant to standard therapy. Both patients achieved CMV DNA clearance within 30 and 18 days; however, the UL97 C480F variant emerged, causing recurrent CMV infection after a cumulative 2 months of MBV and 15 or 4 weeks of ganciclovir treatment, respectively. C480F was not detected under ganciclovir before MBV treatment. Recombinant phenotyping showed that C480F conferred the highest level of MBV resistance and ganciclovir cross-resistance, with impaired viral growth. Clinical follow-up and genotypic and phenotypic studies are essential for the assessment and optimization of patients with suspected MBV resistance.

Automated summary

For transplant recipients with CMV infection resistant to standard therapy, MBV could be an effective treatment option. However, the emergence of MBV resistance should be carefully monitored through clinical follow-up and genotypic and phenotypic studies.