Emergence of letermovir resistance in a lung transplant recipient with ganciclovir-resistant cytomegalovirus infection

Lauren Cherrier, Aasya Nasar, Kellie J. Goodlet, Michael D. Nailor, Sofya Tokman, Sunwen Chou

Research output: Contribution to journalArticlepeer-review

80 Scopus citations


Following a year of valganciclovir prophylaxis, a lung transplant recipient developed cytomegalovirus (CMV) infection that became resistant to ganciclovir, as confirmed by detection of UL97 kinase mutation M460V and a previously uncharacterized UL54 DNA polymerase mutation L516P. The latter mutation is now shown to confer ganciclovir and cidofovir resistance. As predicted from the viral genotype, foscarnet therapy was effective, but resumption of valganciclovir as secondary prophylaxis resulted in a plasma viral load rebound to 3.6 log10 copies/mL several weeks later. Valganciclovir was then replaced by letermovir, resulting in gradual viral load reduction in the first 5 weeks to below the quantitation limit (2.7 log10 copies/mL) for 1 week, followed by 10 weeks of rising viral loads reaching 4.3 log10 copies/mL while on letermovir. At this point, CMV genotypic testing revealed UL56 mutation C325Y, which confers absolute resistance to letermovir. Retreatment with foscarnet was successful. This case adds to the considerable list of proven ganciclovir resistance mutations, and provides an early experience with letermovir resistance after off-label therapeutic use. This experience is consistent with in vitro observations of rapid emergence of letermovir-resistant CMV after drug exposure.

Original languageEnglish (US)
Pages (from-to)3060-3064
Number of pages5
JournalAmerican Journal of Transplantation
Issue number12
StatePublished - Dec 2018


  • antibiotic: antiviral
  • antibiotic: antiviral-ganciclovir/valganciclovir
  • clinical research/practice
  • infection and infectious agents - viral: Cytomegalovirus (CMV)
  • infectious disease
  • off-label drug use
  • translational research/science

ASJC Scopus subject areas

  • Immunology and Allergy
  • Transplantation
  • Pharmacology (medical)


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