Cytomegalovirus antiviral resistance among participants in the phase 3 trial of letermovir vs valganciclovir prophylaxis in kidney transplant recipients.

BACKGROUND:In a phase 3 trial, letermovir was non-inferior to valganciclovir for CMV disease prophylaxis in CMV-seronegative (R-) kidney transplant recipients (KTRs) who received a kidney from a CMV-seropositive donor (D+). Genotypic antiviral resistance and CMV glycoprotein B (gB) genotype are reported. METHODS:Plasma samples with detectable CMV DNA were sequenced for presence of known letermovir and valganciclovir resistance-associated amino acid substitutions (RASs) encoded by CMV gene regions (UL51, UL56, UL89, UL54, UL97) and prevalence of gB (UL55) genotypes (gB1-gB5). RESULTS:84 of 292 participants in the letermovir and 93 of 297 in the valganciclovir group had evaluable data for ≥1 gene target. Letermovir RASs were not detected in participants who received letermovir prophylaxis; however, 3 had valganciclovir RASs (pUL97). Twelve participants in the valganciclovir group had valganciclovir RASs (pUL54, pUL97); and 1 who did not receive letermovir during the trial also had letermovir RASs (pUL56). All but 1 participant responded to valganciclovir treatment irrespective of breakthrough CMV DNAemia or frequency of RASs. gB1 was the most frequent genotype across all participants and subgroups. CONCLUSION:Letermovir RASs were not detected in the letermovir group, supporting a low risk for development of resistance with letermovir prophylaxis in CMV D+R- KTRs. CLINICAL TRIALS REGISTRATION:ClinicalTrials.gov: NCT03443869, EudraCT: 2017-001055-30.