Letermovir (Monograph)

Brand name: Prevymis
Drug class: CMV Antivirals

Medically reviewed by Drugs.com on Jun 10, 2025. Written by ASHP.

Introduction

Antiviral; DNA terminase complex inhibitor active against cytomegalovirus (CMV).

Uses for Letermovir

Prevention of CMV Infection and Disease in Hematopoietic Stem Cell Transplant (HSCT) Recipients

Prophylaxis of CMV infection and disease in adult and pediatric patients ≥6 months of age and weighing ≥6 kg who are CMV-seropositive recipients (R⁺) of an allogeneic HSCT. Designated an orphan drug by FDA for prevention of CMV viremia and disease in at-risk populations.

American Society for Transplantation and Cellular Therapy (ASTCT) practice guideline recommends letermovir for adult CMV seropositive allogeneic HSCT recipients to begin no later than 28 days after HSCT and continuing through day 100.

Prevention of CMV Disease in Kidney Transplant Recipients

Prophylaxis of CMV disease in adult and pediatric patients ≥12 years of age and weighing ≥40 kg who are kidney transplant recipients at high risk (e.g., donor is CMV seropositive and recipient is CMV seronegative). Designated an orphan drug by FDA for prevention of CMV viremia and disease in at-risk populations.

Prevention of CMV Disease in Thoracic Organ Transplant Recipients

Letermovir has been used to prevent CMV disease in adult thoracic organ recipients (i.e., lung and/or heart) at high risk ^{† [off-label]} (donor is CMV seropositive and recipient is CMV seronegative). Therapy may be an option for patients who are unable to tolerate standard of care valganciclovir prophylaxis due to adverse effects (e.g., myelosuppression) or resistance.

Letermovir Dosage and Administration

General

Patient Monitoring

• Monitor HSCT recipients for CMV reactivation after completion of letermovir prophylaxis.

• Closely monitor S_cr levels in patients with a Cl_cr <50 mL/min administered letermovir injection.

Administration

Administer orally (tablets or pellets) or by IV infusion.

Use IV letermovir only in patients unable to receive the drug orally. In those receiving IV letermovir, switch to an oral formulation as soon as patient is able to receive oral drugs. Do not administer IV letermovir for more than 4 weeks, if possible.

Oral Administration

Tablets

Administer orally without regard to food. Swallow tablet whole.

Pellets

Mix letermovir oral pellets with soft food or administer via a nasogastric tube (NG tube) or gastric tube (G tube). Do not crush or chew pellets.

Oral pellets may be mixed with 1 to 3 teaspoons of at or below room temperature soft food (e.g., applesauce, yogurt, pudding). Do not use hot food for mixture. After mixing oral pellets with soft food, administer entire mixture within 10 minutes.

For administration down a NG tube or G tube, initially pour letermovir oral pellets into a medicine cup containing room temperature water and then wait 10 minutes. Oral pellets will not dissolve but will become loose or broken up; do not shake or swirl the medicine cup. Stir mixture with a syringe and administer right away using the syringe and NG or G tube. Following administration, add additional room temperature water to the medicine cup for rinsing, stir with a syringe and administer entire rinse mixture using the syringe and NG or G tube. Administer entire mixture within 2 hours. Flush the NG or G tube with the volume of water recommended by NG or G tube manufacturer. Tables 1 and 2 provide further recommendations for the administration of oral pellets via a NG or G tube.

With ENFit syringe, a medicine straw (large bore) is needed to aid withdrawal of the mixture from the medicine cup.

With ENFit syringe, a medicine straw (large bore) is needed to aid withdrawal of the mixture from the medicine cup.

IV Infusion

Administer by IV infusion through peripheral catheter or central venous line only through a sterile 0.2 or 0.22 micron polyethersulfone (PES) in-line filter. Do not administer by rapid IV injection.

Available as preservative-free, sterile concentrate for injection in a single-dose vial that must be diluted prior to IV infusion.

Dilution

Dilute letermovir in commercially available single-dose vials containing 240 or 480 mg of the drug (20 mg/mL) with 0.9% sodium chloride injection or 5% dextrose injection prior to IV infusion. Letermovir is compatible only with 0.9% sodium chloride or 5% dextrose and should not be diluted using any other infusion fluids.

Diluted solution should appear clear and may range from colorless to yellow in color. Tables 3 and 4 provide information on the preparation of various doses of IV letermovir. After preparation, mix infusion bag gently; do not shake.

Must be used with compatible IV bag materials, infusion set materials, plasticizers, and catheters.

Compatible IV bag materials: Polyvinyl chloride (PVC), ethylene vinyl acetate (EVA), polyolefin (polypropylene and polyethylene).

Compatible infusion set materials: PVC, polyethylene (PE), polybutadiene (PBD), silicone rubber (SR), styrene-butadiene copolymer (SBC), styrene-butadiene-styrene copolymer (SBS), polystyrene (PS). Use with polyurethane-containing IV administration set tubing not recommended.

Compatible plasticizers: Tris [2-ethylhexyl] trimelliatate (TOTM), benzyl butyl phthalate (BBP). Do not use with IV bags and infusion set materials containing the plasticizer diethylhexyl phthalate (DEHP).

Compatible catheters: Radiopaque polyurethane.

Rate of Administration

Administer by IV infusion over 1 hour.

Dosage

Pediatric Patients

Prevention of CMV Infection and Disease

CMV-seropositive Allogeneic HSCT Recipients

Oral or IV

≥12 years of age and weighing ≥30 kg: 480 mg once daily.

Initiate between Day 0 and Day 28 after HSCT (before or after engraftment) and continue through day 100 posttransplantation. May continue through day 200 after HSCT in patients at risk for late CMV infection and disease.

6 months to <12 years of age OR ≥12 years of age and weighing <30 kg: Dosage based on weight and summarized in Table 5 (tablets or pellets) and Table 6 (injection). Administer once daily. Dosage adjustments may be needed for pediatric patients <12 years of age when switching between oral and IV formulations.

Initiate between Day 0 and Day 28 after HSCT (before or after engraftment) and continue through day 100 posttransplantation. May continue through day 200 after HSCT in patients at risk for late CMV infection and disease.

High-Risk Kidney Transplant Recipients

Oral or IV

≥12 years of age and weighing ≥40 kg: 480 mg once daily.

Initiate between Day 0 and Day 7 posttransplant and continue through day 200 posttransplantation.

Adults

Prevention of CMV Infection and Disease

CMV-seropositive Allogeneic HSCT Recipients

Oral or IV

480 mg once daily.

Initiate between Day 0 and Day 28 after HSCT (before or after engraftment) and continue through day 100 posttransplantation. May continue through day 200 after HSCT in patients at risk for late CMV infection and disease.

High-Risk Kidney Transplant Recipients

Oral or IV

480 mg once daily.

Initiate between day 0 and day 7 after transplantation and continue through day 200.

Coadministration with Cyclosporine

Adults and pediatric patients ≥12 years of age and weighing ≥30 kg who are HSCT recipients or adults and pediatric patients ≥12 years of age and weighing ≥40 kg who are kidney transplant recipients: Reduce dosage of oral or IV letermovir to 240 mg once daily with coadministration of cyclosporine.

If cyclosporine therapy is initiated after letermovir therapy, reduce next dose of letermovir to 240 mg once daily. If cyclosporine therapy is discontinued after letermovir therapy is initiated, increase next dose of letermovir to 480 mg once daily. If cyclosporine therapy is interrupted due to high serum cyclosporine levels, dosage adjustment of letermovir is unnecessary.

Pediatric patients 6 months to <12 years of age or ≥12 years of age and weighing <30 kg who are HSCT recipients: Recommended letermovir dosage may require adjustment (Table 7).

If cyclosporine therapy is initiated after letermovir therapy, next dose of letermovir should be the daily oral or IV dose coadministered with cyclosporine (Table 7). If cyclosporine therapy is discontinued after letermovir therapy is initiated, next dose of letermovir should be the daily oral or IV dose administered without cyclosporine (Table 5 or Table 6). If cyclosporine therapy is interrupted due to high serum cyclosporine levels, dosage adjustment of letermovir is unnecessary.

Special Populations

Hepatic Impairment

Oral or IV

Mild or moderate hepatic impairment (Child-Pugh class A or B): Dosage adjustments not needed based on hepatic function.

Severe hepatic impairment (Child-Pugh class C): Not recommended.

Renal Impairment

Oral or IV

Cl_cr >10 mL/minute: Dosage adjustments not needed based on renal function.

End-stage renal disease (Cl_cr ≤10 mL/minute), including those receiving dialysis: Data insufficient to make dosage recommendations; safety not known.

IV

Cl_cr <50 mL/minute: Accumulation of the IV vehicle (i.e., hydroxypropyl betadex) may occur.

Geriatric Patients

Dosage adjustments based on age not needed.

Cautions for Letermovir

Contraindications

• Concomitant use with pimozide or ergot alkaloids.

• Concomitant use with pitavastatin or simvastatin in patients also receiving concomitant cyclosporine.

Warnings/Precautions

Risk of Adverse Reactions or Reduced Therapeutic Effect Due to Drug Interactions

Concomitant use with certain drugs may result in clinically important drug interactions, which could lead to adverse effects or reduced therapeutic effect of letermovir or concomitant drugs.

Consider potential for drug interactions prior to and during therapy. Review concomitant drugs and monitor for adverse effects associated with letermovir and concomitant drugs.

Risks Associated with Hydroxypropyl Betadex Excipient in IV Formulation

IV formulation of letermovir contains hydroxypropyl betadex. Hydroxypropyl betadex associated with ototoxicity in animal studies.

When IV letermovir is used in adult patients with Cl_cr <50 mL/minute and in pediatric patients with a similar degree of renal impairment (based on age-appropriate assessment of renal function), accumulation of hydroxypropyl betadex may occur. Monitor S_cr levels closely in these patients.

Administer IV letermovir only to patients unable to take oral therapy and switch these patients to oral letermovir as soon as they can take oral medications. Do not administer IV letermovir for more than 4 weeks, if possible.

Specific Populations

Pregnancy

No adequate human data to assess if letermovir adversely affects pregnancy outcomes.

In animal studies, embryofetal developmental toxicity (including fetal malformations) observed in rats during organogenesis. No embryofetal developmental toxicity observed in rabbits at exposures that were not maternally toxic. In a rat pre- and post-natal development study, total litter loss observed at maternal letermovir exposures approximately 2-fold higher than human exposures at recommended human dosage.

Lactation

Distributed into milk in lactating rats and present in blood of nursing pups.

Not known if distributed into human milk, affects milk production, or affects breast-fed child.

Consider developmental and health benefits of breast-feeding along with the mother's clinical need for the drug and potential adverse effects on the breast-fed child from letermovir or the underlying maternal condition.

Pediatric Use

Safety and efficacy established for prophylaxis of CMV infection and disease in CMV-seropositive recipients of an allogeneic HSCT ≥6 months of age and weighing ≥6 kg and prophylaxis of CMV disease in kidney transplant recipients ≥12 years of age and weighing ≥40 kg who are at high risk.

Females and Males of Reproductive Potential

No data on effect on human fertility; decreased fertility due to testicular toxicity observed in male rats.

Geriatric Use

Safety and efficacy similar between older and younger adults.

Data indicate age (18–78 years of age) does not have a clinically important effect on pharmacokinetics. Dosage adjustments based on age not needed.

Hepatic Impairment

Not recommended in patients with severe hepatic impairment (Child-Pugh class C).

Dosage adjustments not needed in patients with mild or moderate hepatic impairment (Child-Pugh class A or B).

Renal Impairment

Safety in adult patients with end-stage renal disease (Cl_cr ≤10 mL/minute), including those receiving dialysis, and in pediatric patients with a similar degree of renal impairment (based on age-appropriate assessment of renal function) not known. Dosage adjustments not needed in adult patients with Cl_cr >10 mL/minute and in pediatric patients with a similar degree of renal impairment (based on age-appropriate assessment of renal function).

If IV letermovir used in adult patients with Cl_cr <50 mL/minute and in pediatric patients with a similar degree of renal impairment (based on age-appropriate assessment of renal function), closely monitor S_cr concentrations; accumulation of IV vehicle (i.e., hydroxypropyl betadex) could occur.

Common Adverse Effects

Most common adverse effects (incidence ≥10% and at a frequency ≥2% more than placebo) in adults with HSCT: nausea, diarrhea, vomiting, peripheral edema, cough, headache, fatigue, abdominal pain.

Most common adverse effect (incidence ≥10% and at a frequency greater than valgancyclovir) in adults with kidney transplantation: diarrhea.

Adverse events in pediatric patients similar to adults.

Drug Interactions

Substrate of CYP3A and 2D6. Moderate inhibitor of CYP3A; also induces CYP3A. Reversible inhibitor of CYP2C8. Expected to induce CYP2C9 and 2C19. Not metabolized by CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2E1, or 4A11; does not inhibit CYP1A2, 2A6, 2C9, 2C19, 2D6, or 2E1; and does not induce CYP1A2.

Substrate of organic anion transporter polypeptide (OATP) 1B1 and 1B3. Inhibits OATP1B1, 1B3, and renal organic anion transporter (OAT) 3; does not inhibit OAT2B1 or OAT1. Transport not mediated by OATP2B1 or OAT1.

Metabolized by UGT1A1 and 1A3 to a minor extent. Not metabolized by UGT1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, or 2B17; does not inhibit UGT1A4, 1A6, 1A9, or 2B7.

Substrate and inhibitor of P-glycoprotein (P-gp) transport.

Inhibits breast cancer resistance protein (BCRP), bile salt export pump (BSEP), and multidrug resistance-associated protein (MRP) 2. Does not inhibit renal organic cation transporter (OCT) 1 or 2 and is not transported by OCT1, BCRP, or MRP2.

Drugs Affecting or Metabolized by Hepatic Microsomal Enzymes

CYP3A substrates: Clinically important increased concentrations of such substrates may occur. Magnitude of CYP3A-mediated drug interactions may be different when letermovir used concomitantly with cyclosporine.

CYP2C8 substrates: Possible increased concentrations of such substrates.

CYP2C9 or 2C19 substrates: Possible decreased concentrations of such substrates.

Drugs Affecting or Affected by Organic Anion Transporters

OATP1B1 or 1B3 inhibitors: Possible increased letermovir concentrations.

OATP1B1 or 1B3 substrates: Clinically important increased concentrations of such substrates may occur. Magnitude of OATP1B1- or 1B3-mediated drug interactions may be different when letermovir used concomitantly with cyclosporine.

Drugs Affecting or Metabolized by UGT

UGT inducers: Concomitant administration with drugs that induce UGT not recommended due to potential for decreased letermovir plasma concentrations.

Drugs Affected by P-glycoprotein Transport

P-gp inducers: Concomitant administration with drugs that induce P-gp transporters not recommended due to potential for decreased letermovir plasma concentrations.

Drugs Affecting or Affected by Other Membrane Transporters

BCRP, BSEP, and MRP2 substrates: Concomitant use not evaluated; clinical effect of letermovir on such substrates not known.

Specific Drugs

Letermovir Pharmacokinetics

Absorption

Bioavailability

240–480 mg orally (without cyclosporine) in healthy individuals: 94%.

480 mg orally (without cyclosporine) in HSCT recipients: 35%.

240 mg orally (with cyclosporine) in HSCT recipients: 85%.

Food

When administered orally with food, peak plasma concentrations 30% higher and AUC similar to that observed when administered in fasting state.

Plasma Concentrations

Oral: Peak plasma concentrations occur 1.5—3.0 hours after a dose.

IV: Peak plasma concentrations occur at end of infusion.

Steady-state concentrations achieved within 9–10 days.

AUC and peak plasma concentration were comparable when comparing letermovir oral tablet and pellets at 240 mg dose.

Distribution

Plasma Protein Binding

99%.

Elimination

Metabolism

Metabolized to minor extent by UGT1A1 and 1A3.

Elimination Route

Eliminated via hepatic uptake by OATP1B1 and 1B3.

Following single oral dose, 93% excreted in feces (70% as unchanged drug) and <2% excreted in urine.

Half-life

Following IV administration, mean terminal half-life is 12 hours.

Special Populations

Hepatic impairment: AUC approximately 1.6- or 3.8-fold higher in individuals with moderate or severe hepatic impairment (Child-Pugh class B or C), respectively, compared with healthy individuals.

Renal impairment: AUC approximately 1.9- or 1.4-fold higher in individuals with moderate or severe renal impairment, respectively, compared with healthy individuals. Not known if dialysis removes letermovir from systemic circulation.

Stability

Storage

Oral

Tablets and Pellets

20–25°C (may be exposed to 15–30°C). Store in original package until use.

Parenteral

Concentrate for Injection, for IV Infusion

20–25°C (may be exposed to 15–30°C). Store in original carton; protect from light.

Following dilution with 0.9% sodium chloride or 5% dextrose, stable at room temperature for up to 24 hours or under refrigeration (2–8°C) for up to 48 hours; this includes storage in the IV bag and duration of IV infusion.

Actions and Spectrum

• Quinazoline antiviral; CMV DNA terminase complex inhibitor.

• CMV DNA terminase complex is a heterodimeric enzyme with several protein subunits (pUL51, pUL56, pUL89) and is required for viral DNA processing and packaging. By inhibiting the terminase complex, letermovir interferes with production of proper-length genomes and virion maturation.

• Letermovir has a very limited spectrum of antiviral activity. Active in vitro and in vivo against human CMV (HCMV), a human herpes virus. More potent than ganciclovir against susceptible CMV in vitro and has been active in vitro against some ganciclovir-resistant strains. No inhibitory activity in vitro against other herpes viruses or other important human pathogenic viruses tested, including adenovirus type 2, Epstein-Barr virus (EBV), HBV, HCV, herpes simplex virus types 1 and 2 (HSV-1, HSV-2), human herpesvirus type 6 (HHV-6), HIV type 1 (HIV-1), influenza virus type A, and varicella-zoster virus (VZV).

• CMV mutants with reduced susceptibility to letermovir selected in vitro in cell culture. Letermovir resistance-associated substitutions reported in some patients who experienced treatment failure, including novel substitutions.

• Cross-resistance between letermovir and antivirals in other classes (e.g., DNA polymerase inhibitors) unlikely. Letermovir has been active against CMV with substitutions conferring resistance to DNA polymerase inhibitors (e.g., cidofovir, foscarnet, ganciclovir) and these DNA polymerase inhibitors have been active against CMV isolates with substitutions conferring resistance to letermovir.

Advice to Patients

• Advise patients to read the patient information provided by the manufacturer (Patient Information and Instructions for Use).

• Inform patients of the importance of not missing or skipping doses and continuing letermovir for the duration recommended by the clinician. Instruct patients that if they miss a dose of letermovir, they should take it as soon as they remember. If they do not remember until it is time for the next dose, instruct them to skip the missed dose and go back to the regular schedule. Instruct patients not to double their next dose or take more than the prescribed dosage.

• If using letermovir tablets, advise patients that the tablets may be taken without regard to food and should be swallowed whole. Advise patients or caregivers to read and follow the instructions for use when preparing letermovir oral pellets for administration. Advise patients that IV letermovir should only be used in patients unable to take oral therapy and these patients should be switched to oral therapy as soon as possible.

• Inform patients that the IV formulation contains hydroxypropyl betadex, which may accumulate in patients with renal impairment and potentially cause ototoxicity.

• Advise patients to store letermovir tablets and oral pellets in the original package until use.

• Stress importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as any concomitant illnesses.

• Advise patients to inform clinicians if they are or plan to become pregnant or plan to breast-feed.

• Advise patients of other important precautionary information.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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