A trial of Moderna’s norovirus vaccine in the U.S. has been put on hold by the FDA over a reported case of neurological disorder.
The phase 3 study is evaluating the candidate, dubbed mRNA-1403, across two norovirus seasons. The trial is already fully enrolled in the Northern Hemisphere—with the first patient dosed last September—and Moderna is preparing for enrollment for the other norovirus season in the Southern Hemisphere.
The goal is to recruit around 20,000 participants aged 60 years and older as well as 5,000 participants between the ages of 18 and 59. The trial’s aim is to assess mRNA-1403’s ability to protect against moderate to severe norovirus acute gastroenteritis in adults, with “a focus on the older age group that is at greatest risk of severe outcomes including hospitalization,” Moderna has previously said.
However, in its fourth-quarter earnings release this morning, the biopharma announced that the trial has been placed on hold by the FDA “following a single adverse event report of a case of Guillain-Barré syndrome.”
Guillain-Barré syndrome is a rare autoimmune disorder that causes the body's immune system to attack the nerves. The syndrome has cropped up as a side effect in trials for RSV vaccines like Pfizer’s Abrysvo and GSK’s Arexvy.
The single case of Guillain-Barré syndrome in the mRNA-1403 trial is “currently under investigation,” Moderna said in the Feb. 14 release.
“The company does not expect an impact on the study's efficacy readout timeline as enrollment in the Northern Hemisphere has already been completed,” Moderna added. “The timing of the phase 3 readout will be dependent on case accruals.”
Moderna's president, Stephen Hoge, M.D., expanded on the news, pointing out in a call with investors this morning that “GBS does happen.”
“It’s usually seen in older adults—about one to two per 100,000 people per year—and given we’ve enrolled a little over 250,000 patients in studies over the last couple of years, it wouldn’t be surprising to see cases in our clinical trials,” Hoge explained.
“As relates to this case, when we identified it, we proactively decided to pause our activities and update our study documents,” Hoge said, adding that “we really don’t expect there to be any impact on the conduct of the study or the timeline for readout on efficacy.”
“From our side, this is just about being prudent and transparent and making sure that we’re prioritizing patient safety,” he stressed.
Designed to protect against multiple norovirus genotypes, Moderna's mRNA-1403 is a trivalent formulation that contains mRNA encoded for virus-like particles.