Moderna Announces Phase 3 Study of Investigational Cytomegalovirus (CMV) Vaccine Did Not Meet Primary Efficacy Endpoint

Rhea-AI Summary

Moderna (NASDAQ: MRNA) announced that its Phase 3 pivotal trial of investigational CMV vaccine mRNA-1647 did not meet the primary efficacy endpoint in seronegative women aged 16–40, and the company will discontinue its congenital CMV development program.

The randomized, observer-blind, placebo-controlled trial enrolled ~7,500 women across ~300 sites in 13 countries. Vaccine efficacy against primary CMV infection ranged from 6% to 23% depending on case definition. mRNA-1647 was generally well tolerated and no safety concerns were reported by the Data and Safety Monitoring Board. Moderna will continue a Phase 2 study of mRNA-1647 in bone marrow transplant patients and does not expect any impact to its 2025 financial guidance or its expectation of achieving breakeven in 2028.

Positive

• Large Phase 3 trial enrolled ~7,500 participants across 13 countries
• mRNA-1647 showed generally well-tolerated safety profile
• Company will continue Phase 2 study in bone marrow transplant patients
• No safety concerns raised by the Data and Safety Monitoring Board
• Company does not expect impact to 2025 financial guidance

Negative

• Phase 3 failed primary efficacy endpoint in seronegative women 16–40
• Moderna will discontinue congenital CMV clinical development program
• Vaccine efficacy only ranged from 6% to 23% by case definition
• Expected initial revenue from mRNA-1647 was minimal and now lost

Insights

Senior Biotech Strategy Expert

Phase 3 failed to meet primary endpoint; congenital CMV program discontinued — clear negative near-term clinical and strategic impact.

Moderna halted its congenital CMV development after a Phase 3 pivotal study in ~7,500 seronegative women across ~300 sites in 13 countries failed to meet the primary efficacy endpoint, with vaccine efficacy reported between 6% and 23% depending on case definition. The company will discontinue the congenital program while continuing a Phase 2 study of mRNA-1647 in bone marrow transplant patients; safety data raised no new concerns according to the Data and Safety Monitoring Board.

Stopping a late‑stage program removes a potential future product and eliminates associated launch investments, which explains management’s statement that 2025 guidance and the plan to reach breakeven in 2028 remain unchanged. Key dependencies and risks now include the remaining Phase 2 bone marrow transplant data and public disclosure of the full Phase 3 dataset, both of which determine whether mRNA-1647 has any viable niche use; regulatory or peer scrutiny of the topline definitions that produced the 6%-23% efficacy range could also influence interpretation.

Watch for the full Phase 3 dataset release and scientific presentations in the near term to clarify case definitions and subgroup results, and monitor the ongoing Phase 2 transplant trial (NCT05683457) for efficacy signals and timelines; these items are the immediate determinants of any residual value for mRNA-1647 over the next 6-18 months.

Company to discontinue development of mRNA-1647 in congenital CMV

Company will continue to evaluate mRNA-1647 in ongoing Phase 2 trial in bone marrow transplant patients

Company does not anticipate any impact to its 2025 financial guidance or its expectation of achieving breakeven in 2028

CAMBRIDGE, MA / ACCESS Newswire / October 22, 2025 / Moderna, Inc. (NASDAQ:MRNA) today 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.

"Today's 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.

About Moderna

Moderna is a leader in the creation of the field of mRNA medicine. Through the advancement of mRNA technology, Moderna is reimagining how medicines are made and transforming how we treat and prevent disease for everyone. By working at the intersection of science, technology and health for more than a decade, the company has developed medicines at unprecedented speed and efficiency, including pioneering work on COVID-19 vaccines.

Moderna's mRNA platform has enabled the development of therapeutics and vaccines for infectious diseases, immuno-oncology, rare diseases and autoimmune diseases. With a unique culture and a global team driven by the Moderna values and mindsets to responsibly change the future of human health, Moderna strives to deliver the greatest possible impact to people through mRNA medicines. For more information about Moderna, please visit modernatx.com and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including statements regarding: Moderna's 2025 financial guidance and its expectation of achieving breakeven in 2028; and the potential of mRNA-1647 for bone marrow transplant patients and Moderna's ongoing Phase 2 trial. The forward-looking statements in this press release are neither promises nor guarantees, and you should not place undue reliance on these forward-looking statements because they involve known and unknown risks, uncertainties, and other factors, many of which are beyond Moderna's control and which could cause actual results to differ materially from those expressed or implied by these forward-looking statements. These risks, uncertainties, and other factors include, among others, those risks and uncertainties described under the heading "Risk Factors" in Moderna's Annual Report on Form 10-K for the fiscal year ended December 31, 2024, and in subsequent filings made by Moderna with the U.S. Securities and Exchange Commission, which are available on the SEC's website at www.sec.gov. Except as required by law, Moderna disclaims any intention or responsibility for updating or revising any forward-looking statements contained in this press release in the event of new information, future developments or otherwise. These forward-looking statements are based on Moderna's current expectations and speak only as of the date of this press release.

Moderna Contacts

Media:

Chris Ridley
Head of Global Media Relations
+1 617-800-3651
Chris.Ridley@modernatx.com

Investors:

Lavina Talukdar
Senior Vice President & Head of Investor Relations
+1 617-209-5834
Lavina.Talukdar@modernatx.com

SOURCE: Moderna, Inc.

View the original press release on ACCESS Newswire

FAQ

What did Moderna (MRNA) announce about the mRNA-1647 Phase 3 CMV trial on October 22, 2025?

Moderna announced the Phase 3 trial did not meet its primary efficacy endpoint and it will discontinue the congenital CMV program.

How many participants were in Moderna's Phase 3 CMV vaccine trial (MRNA)?

The randomized trial included approximately 7,500 women across about 300 sites in 13 countries.

What was the measured efficacy range for mRNA-1647 in the Phase 3 CMV trial (MRNA)?

Vaccine efficacy against primary CMV infection ranged from 6% to 23% depending on the case definition used.

Will the Phase 3 CMV failure affect Moderna's 2025 guidance or breakeven expectation (MRNA)?

Moderna stated it does not anticipate any impact to its 2025 financial guidance or its expectation of achieving breakeven in 2028.

Is Moderna continuing any development of mRNA-1647 after the Phase 3 result (MRNA)?

Yes. Moderna will continue to evaluate mRNA-1647 in an ongoing Phase 2 trial in bone marrow transplant patients.

Were there any safety concerns from the Phase 3 CMV trial for mRNA-1647 (MRNA)?

No safety concerns were reported by the Data and Safety Monitoring Board; mRNA-1647 was generally well tolerated.