Merck announced that the Food and Drug Administration (FDA) has approved Prevymis (letermovir) tablets and intravenous (IV) injection for prophylaxis of cytomegalovirus (CMV) infection and disease in adult CMV-seropositive recipients (R+) of an allogeneic hematopoietic stem cell transplant (HSCT).

The FDA approval was based on data from a Phase 3 multicenter, double-blind, placebo-controlled trial (n=565) in adult CMV R+ patients of an allogeneic HSCT who were randomized to Prevymis 480mg once daily (adjusted to 240mg for concomitant drugs) or placebo. Patients were monitored up to Week 24 post-transplant for the incidence of clinically significant CMV infection, and then further monitored through Week 48 post-transplant.

The data showed significantly fewer patients treated with Prevymis vs. placebo (38% vs. 61%) developed clinically significant CMV infection, stopped treatment or had missing data through Week 24 post-HSCT (difference –23.5, 95% CI: –2.5 to –14.6; P<0.0001). A significant benefit was seen with Prevymis vs. placebo in time to clinically significant CMV infection through Week 24 post-HSCT (cumulative rate: 18.9% vs. 44.3%; P<0.0001). 

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All-cause mortality was also lower in Prevymis-treated patients vs placebo at Week 24 post-transplant (12% vs. 17%). Bone marrow suppression occurrence was similar for both groups. In addition, the median time to engraftment was 19 days in the Prevymis treatment arm vs. 18 in the placebo arm. 

Prevymis, a non-nucleoside CMV inhibitor (3,4 dihydro-quinazoline), inhibits viral replication through targeting the viral terminase complex. Prevymis will be available as 240mg and 480mg strength tablets in 4 Dosepaks, each containing a 7-count blister card (28 tablets total) or as a carton containing 2 blister cards, each containing a 7-count blister card (14 tablets total). Prevymis injection will be available in 240mg  (12mL vial) and 480mg (24mL vial) strengths in single-dose vials. Both formulations are anticipated to launch in December. 

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