Moderna, Inc. (MRNA) said the US Food and Drug Administration's Centre for Biologics Evaluation and Research (CBER) has issued a Refusal-to-File letter RTF and has notified the firm that it will not initiate a review of the biologics license application (BLA) for its investigational influenza vaccine, mRNA-1010.
Following the news, MRNA slipped by 10.01%, to $37.79 in the overnight trading.
THE RTF letter identified the choice of a licensed standard-dose seasonal influenza vaccine comparator as the reason for the refusal to initiate the review of Moderna's application. Specifically, the letter cited the lack of an adequate, well-controlled study with a comparator arm that does not reflect the best available standard of care.
Moderna has requested a Type A meeting with CBER to understand the basis for the RTF letter.
In addition, Moderna also noted that it does not expect any impact on its 2026 financial guidance.
In August of 2025, following the completion of the Phase 3 efficacy trial in which mRNA-1010 met all agreed-upon pre-specified primary endpoints, Moderna held a pre-submission meeting with CBER.
In a written feedback, CBER requested that supportive analyses on the comparator be included in the submission and indicated that the data would be a "significant issue during review of your BLA."
In response, Moderna provided the additional analyses requested by CBER in its submission, including data from a separate Phase 3 trial (P303 Part C) comparing mRNA-1010 against a licensed high-dose influenza vaccine.
P303 Part C was a safety and immunogenicity study that compared mRNA-1010 against a high-dose comparator in adults aged 65 years or older. P304 was a safety and relative efficacy study that compared mRNA-1010 against a licensed standard-dose comparator in adults aged 50 years and older. In both Phase 3 studies, the primary endpoints showed that mRNA-1010 was statistically superior to the respective comparators.
However, Moderna added that at no time in the pre-submission written feedback or meeting did CBER indicate that it would refuse to review the file.
In April 2024, Moderna had submitted the Phase 3 study protocol to CBER for review during a pre-Phase 3 consultation.
Moderna said that CBER provided written guidance noting, "While we agree it would be acceptable to use a licensed standard dose influenza vaccine as the comparator in your Phase 3 study, we recommend you use a vaccine preferentially recommended for use in older adults by the ACIP (i.e., Fluzone HD, Fluad or Flublok) for participants >65 years of age in the study. Data on the comparative efficacy of your vaccine against an influenza vaccine preferentially recommended for use in the >65 years age group may help inform ACIP's recommendation for the use of your vaccine in the older adult population. If you proceed with using a standard dose influenza vaccine comparator in participants =65 years of age, we agree with your plan to include statements in the Informed Consent Form."
mRNA-1010 has been accepted for review in the EU, Canada and Australia. Submissions in additional countries are planned for 2026.
Moderna expects the earliest potential approvals for mRNA-1010 to begin in late 2026 or early 2027, subject to those ongoing regulatory reviews.
Moderna added that the CBER raised no objections or clinical hold comments regarding the adequacy of the Phase 3 trial after the protocol submission in April 2024, or at any time before the study initiation in September 2024.
In parallel, Moderna noted that both the phase 3 designs were reviewed by the FDA prior to study initiation. Neither the relevant regulation, 21 C.F.R. § 314.126 (Adequate and well-controlled studies), nor the FDA's guidance for industry on seasonal influenza vaccines contains any reference to the use of a comparator reflecting the "best-available standard of care."
"This decision by CBER, which did not identify any safety or efficacy concerns with our product, does not further our shared goal of enhancing America's leadership in developing innovative medicines," said Stéphane Bancel, Chief Executive Officer of Moderna.
MRNA has traded between $22.28 and $55.20 from November 21, 2025, to date. The stock closed Monday's trade at $42, up 0.11%.
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