The U.S. Food and Drug Administration (FDA) has halted clinical trials for Novavax's combination COVID-19 and influenza vaccine, as well as its standalone influenza vaccine candidate, following a report of a serious adverse event. The clinical hold was initiated after a participant in a Phase 2 trial experienced motor neuropathy. This adverse event, reported in September 2024, involved a participant who had received the combination vaccine in January 2023 while enrolled in the trial outside of the United States. The trial had been completed in July 2023.
Details of the Clinical Hold
The FDA's decision, communicated to Novavax on October 16, 2024, stems from a spontaneous report of motor neuropathy, a rare immune-mediated disorder causing muscle weakness in the limbs. Novavax anticipates receiving an official letter from the FDA within 30 days, which is expected to provide further details regarding the hold and the steps required for its resolution. The company acknowledged that the hold could potentially delay the initiation of a planned Phase 3 trial for both the combination and standalone influenza vaccines.
Novavax's Response and Safety Commitment
Robert Walker, MD, Chief Medical Officer of Novavax, stated, "We are working closely with the FDA to provide the necessary information that will allow them to better understand this observation and resolve the clinical hold." He emphasized the company's commitment to safety, adding, "It is important to note that safety is our top priority, and while we do not believe causality has been established for this serious adverse event, we are committed to working expeditiously to fulfill requests for more information from the FDA. Our goal is to successfully resolve this matter and to start our Phase 3 trial as soon as possible."
Impact on Novavax and Future Plans
The clinical hold represents a setback for Novavax, which has been banking on the development of combination vaccines to bolster its market position. Earlier this year, Novavax entered into a deal with Sanofi, where the French pharmaceutical company paid $500 million upfront for rights to co-market Novavax’s COVID-19 vaccine and to develop combination vaccines incorporating Sanofi’s influenza shots. While Novavax retained rights to develop its own combination vaccine, these plans are now facing uncertainty. The company had previously aimed to commence a Phase 3 immunogenicity trial this quarter, with data expected by mid-2025. These timelines are now in question pending the resolution of the clinical hold.
Context of Novavax's Market Entry
Novavax entered the COVID-19 vaccine market later than its competitors, receiving emergency clearance in 2022 as the fourth coronavirus vaccine available in the U.S. The company differentiated itself from Pfizer and Moderna by utilizing a more traditional protein-based technology. However, the vaccine's uptake was slower than anticipated, leading to business plan adjustments, including staff layoffs and spending cuts. Despite these challenges, Novavax continues to focus on combination vaccines and its partnership with Sanofi.
Prior Safety Data and Ongoing Investigations
Novavax has reported that previous trials of its COVID-19 and influenza vaccines have not shown any signals for motor neuropathy. The company has informed investigators of the current clinical hold and is working to provide the FDA with the necessary information to address their concerns. It is important to note that the clinical hold does not affect the COVID-19 IND for Novavax's standalone COVID-19 vaccine, which remains available for use.
