Letermovir

How it works

It inhibits the CMV DNA terminase complex (pUL56), preventing cleavage of viral DNA concatemers and proper packaging of progeny virions, so it acts at a different step from the viral DNA polymerase inhibitors.

Prescribing in practice

• It is a substrate and inhibitor of several enzymes and transporters and notably increases ciclosporin exposure and concentrations of certain statins, so co-medication must be reviewed and potentially dose-adjusted before starting.
• Activity is restricted to CMV, so it offers no protection against other herpesviruses and is not a substitute for broader antiviral cover where indicated.
• Oral and intravenous formulations are available and are considered interchangeable, with route guided by the patient's clinical status and the SPC.

Monitoring

Monitor for CMV reactivation or breakthrough during prophylaxis and review concomitant medication, with closer attention to interacting drugs such as ciclosporin.

Counselling the patient

• Take this medicine to help prevent a reactivation of the CMV virus after your transplant.
• Tell the team about all your other medicines, as letermovir can change how some of them work.
• Report any new fever or feeling unwell so possible CMV infection can be checked.

Evidence & guidelines

Efficacy for CMV prophylaxis after allogeneic stem cell transplantation was demonstrated in a pivotal randomised controlled trial against placebo.