Cambridge:Moderna, Inc. has announced topline results from a Phase 3 pivotal trial evaluating the efficacy of mRNA-1647, the Company's investigational cytomegalovirus (CMV) vaccine. The study did not meet its primary efficacy endpoint of preventing CMV infection in seronegative female participants of childbearing age (16-40 years of age). Moderna will discontinue its congenital CMV clinical development program. "The announcement is disappointing for families and healthcare professionals who have been eagerly awaiting a CMV vaccine to prevent congenital CMV, a leading infectious cause of birth defects," said Stéphane Bancel, Chief Executive Officer of Moderna. "The majority of the data from this trial is still forthcoming, and we will share our full results with the scientific community in hopes that our learnings can contribute to the continued pursuit of a CMV vaccine. I am grateful for our dedicated team, our partners at clinical trial sites, and all the trial participants who made this research possible." The Phase 3 trial (NCT05085366) was a randomized, observer-blind, placebo-controlled study. The study included approximately 7,500 women 16-40 years of age from approximately 300 sites across 13 countries, representing the largest trial assessing the efficacy of a CMV vaccine to-date. Vaccine efficacy against primary CMV infection in healthy women was well below the Company's target, ranging from 6% to 23% depending on the case definition used. "We are clearly disappointed by the failure to prevent primary infection because it means there is still no vaccine for the prevention of congenital CMV despite the many decades of work by the field," said Stephen Hoge, MD, President of Moderna. "CMV does cause significant disease in other contexts, including reactivation of the latent virus in those undergoing bone marrow transplantation, and we will continue to explore the potential of mRNA-1647 to suppress disease associated with reactivation in those high-risk patients through our ongoing Phase 2 study." mRNA-1647 was found to be generally well-tolerated regardless of CMV serostatus, with a safety profile consistent with earlier studies. No safety concerns have been raised by the Data and Safety Monitoring Board. The Company plans to continue its study of mRNA-1647 in bone marrow transplant patients, which is currently in a Phase 2 trial (NCT05683457). Moderna does not anticipate any impact to its 2025 financial guidance or its expectation of achieving breakeven in 2028. Moderna anticipated minimal initial revenue contribution from mRNA-1647 given necessary investments in market building and launch, and expected the product to be cash-flow negative in 2028.