Moderna has scrapped plans to enroll a new cohort in a phase 3 trial of its norovirus vaccine and instead will meet with regulators to decide on next steps.
The mRNA-focused company launched the late-stage trial of the shot, dubbed mRNA-1403, back in September 2024 as the norovirus season kicked off in the Northern Hemisphere. The trivalent vaccine is designed to prevent the inflammation of the stomach, known as acute gastroenteritis.
But Moderna disclosed in July that mRNA-1403 had missed on its interim analysis. At the time, the biopharma's plan was to enroll an additional cohort—but the company appears to have had second thoughts.
“Following a review of the program, we have decided not to enroll an additional cohort this coming winter season,” Moderna President Stephen Hoge, M.D., told analysts on a third-quarter earnings call this morning. “Instead, we are engaging with health authorities to determine the next steps for the program.”
When pushed by analysts for more details on the norovirus strategy, Hoge promised to “provide further updates following those discussions.”
“Once we've had those discussions with them about the potential next steps of the program, we'll be able to provide an update more broadly,” he said on the call.
Moderna reported that its R&D expenses had dropped 27% to $583 million in the third quarter, which the company primarily attributed to “lower clinical development costs following the completion and wind-down of certain late-stage studies in the company's infectious disease portfolio, as well as continued cost efficiencies across the organization.”
Norovirus, otherwise known as the “stomach bug,” is a very contagious virus that causes inflammation of the stomach and can lead to vomiting and diarrhea, with severe cases potentially leading to hospitalization due to dehydration.
Moderna’s mRNA-1403 has hit some roadblocks in the past. In February 2025, it was placed on hold by the FDA over a reported case of Guillain-Barré syndrome, a neurological disorder where the body’s immune system mistakenly attacks the peripheral nervous system. The following November, the study had to head back for a second season in the Northern Hemisphere after failing to find enough cases down south.
Moderna has a clearer route to success for its personalized mRNA cancer vaccine intismeran autogene. Moderna and its partner Merck & Co. unveiled more data from the vaccine's phase 3 melanoma win in combination with Keytruda at the European Society for Medical Oncology conference last month. The partners are currently working toward regulatory submissions and preparing for a potential commercial launch.
“This marked the first combination immunotherapy regimen to demonstrate additional benefit over Keytruda alone in the adjuvant melanoma setting, representing a significant milestone for melanoma patients and their families around the world,” Moderna CEO Stéphane Bancel told analysts on the earnings call.
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