Clinical Trial to Evaluate the Effects of Letermovir Prophylaxis on T-cell Immune Activation in Participants With Treated HIV-1 Infection

Inclusion Criteria: * Is HIV-1 antibody positive with a plasma HIV-1 RNA ≤50 copies/mL for greater than 12 months * ≥50 years of age of any gender * Females of childbearing potential who agree to avoid pregnancy for the duration of the trial and follow methods of contraception as detailed in section 7.1 * Has a nadir CD4 of ≤200 cells/mm3 prior to screening * Has been on antiretroviral therapy for ≥ 6 months * Has documented CMV IgG seropositivity within one year of trial screening * Has an undetectable (≤168 international units/mL) CMV Deoxyribonucleic acid (DNA) within 14 days prior to randomisation * Laboratory parameters are not clinically significant as determined by the investigator * The participant (or legally acceptable representative, if applicable) has provided written informed consent for the trial and Future Biomedical Research Exclusion Criteria: * Is HIV-1 antibody positive with a plasma HIV-1 RNA ≤50 copies/mL for greater than 12 months * ≥50 years of age of any gender * Females of childbearing potential who agree to avoid pregnancy for the duration of the trial and follow methods of contraception as detailed in section 7.1 * Has a nadir CD4 of ≤200 cells/mm3 prior to screening * Has been on antiretroviral therapy for ≥ 6 months * Has documented CMV IgG seropositivity within one year of trial screening * Has an undetectable (≤168 international units/mL) CMV Deoxyribonucleic acid (DNA) within 14 days prior to randomisation * Laboratory parameters are not clinically significant as determined by the investigator * The participant (or legally acceptable representative, if applicable) has provided written informed consent for the trial and Future Biomedical Research Main Exclusion criteria: * Has a history of ulcerative colitis or Crohn's disease or active colitis within 6 months prior to randomisation * Has a history of CMV end-organ disease within 6 months prior to randomisation * Has significant hypersensitivity or other contraindication to any of the components of the trial drug as described in the SmPC * Has a detectable HCV RNA or hepatitis B surface antigen (HBsAg) within 90 days prior to randomisation * Has a history of malignancy ≤5 years prior to signing informed consent * Is pregnant or expecting to conceive, is breastfeeding, or plans to breastfeed from the time of consent through 90 days after the last dose of trial therapy * Has received within 7 days prior to screening any of the following: ganciclovir; valganciclovir; foscarnet; acyclovir (≥ 3200 mg PO per day or ≥25 mg/kg IV per day); valaciclovir (≥3000 mg PO per day) or famciclovir (≥1500 mg PO per day). * Has used systemic immunosuppressive therapy or immune modulators within 30 days prior to treatment in this trial or is anticipated to need them during the trial