FDA Accepts Pair of Supplemental New Drug Applications for Anti-CMV Drug Letermovir

Letermovir is the only drug approved for prophylaxis of cytomegalovirus (CMV) infection for patients who are CMV-seropositive and have received an allogeneic HSCT.

The FDA will review 2 supplemental new drug applications (sNDA) for letermovir (Prevymis; Merck). One application is for the use of letermovir as prophylaxis of cytomegalovirus (CMV) disease in adult kidney transplant recipients at high risk (D+/R-). The second sNDA is for the extended use of letermovir (100 days to 200 days) in adults who received an allogeneic hematopoietic stem cell transplant (HSCT) and at risk for CMV infection and disease, to Merck announced in a press release.

The reviews are based on a pair of recent phase 3 trials evaluating letermovir in these patient populations.

“Certain high-risk individuals who develop CMV infection following receipt of a kidney transplant are at increased risk for transplant failure and death. Letermovir (PREVYMIS) has the potential to be an important new option with a favorable safety profile for patients at risk for CMV infection following a kidney transplant,” said Nicholas Kartsonis, senior vice president, vaccines and infectious diseases, Global Clinical Development, Merck Research Laboratories, in the press release.

In a phase 3, randomized, double-blind, clinical trial (NCT03443869), letermovir was evaluated for safety and efficacy against valganciclovir, the current prophylactic standard of care for these patients. Letemorvir showed non-inferior efficacy and a more favorable safety profile, including fewer adverse events (AEs) and study drug discontinuations from AEs.

The trial also showed that AEs such as leukopenia—reduced leukocytes—and neutropenia— reduced neutrophils—were significantly less (38%) with letermovir compared to valganciclovir. Post-transplant, the letermovir cohort experienced neutropenia at more than a 4-fold lower rate, and this cohort was more than 3-times less likely to stop treatment compared to the valganciclovir arm.

A separate phase 3, randomized, double-blind, placebo-controlled trial (NCT03930615) compared the safety and efficacy against a placebo in high-risk CMV-seropositive recipients [R+] following HSCT. It met these endpoints and was shown to prevent CMV for 200 days post-HSCT.

CMV is a common virus that can infect anyone; however, a person with a strong immune system often never presents symptoms or the virus remains inactive in their body—these patients are CMV-seropositive. For transplant patients who do not have CMV (CMV-seronegative) but receive an organ from a doner who is CMV-seropositive, the CMV disease can reactivate in their body, causing potential end-organ damage, and increases their risk of transplant failure or death.

The FDA first approved letermovir in 2017 and it is now approved in more than 60 countries worldwide. It is the only drug approved for this unique patient population.

Data from the recent studies will be presented February 18, 2023, at the 2023 Transplantation & Cellular Therapy Meetings of the American Society for Transplantation and Cellular Therapy and Center for International Blood & Marrow Transplant Research.

“We look forward to the FDA’s review of our filings for letermovir,” Kartsonis said in the press release.


Merck. U.S. FDA Accepts for Priority Review the Supplemental New Drug Application for Merck’s PREVYMIS™ for Prophylaxis of Cytomegalovirus Disease in Kidney Transplant Recipients at High Risk. News Release. February 17, 2023. Accessed February 17, 2023. https://www.merck.com/news/u-s-fda-accepts-for-priority-review-the-supplemental-new-drug-application-for-mercks-prevymis-for-prophylaxis-of-cytomegalovirus-disease-in-kidney-transplant-recipients-at-high-risk/

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