HilleVax's norovirus vaccine fails in large infant trial

Biotechnology company HilleVax announced on Monday that it is discontinuing the development of its experimental norovirus vaccine for infants after it failed to demonstrate efficacy in a large clinical trial. This decision led to a significant drop in the company's stock price. The vaccine, identified as HIL-214, did not achieve its primary or secondary objectives in the Phase 2b study, which aimed to gauge its effectiveness in preventing moderate to severe norovirus-related acute gastroenteritis.

Norovirus currently lacks a vaccine, and HIL-214 was the most advanced candidate in clinical development for this purpose. Despite halting the infant program, HilleVax, based in Boston, is now evaluating the possibility of continuing trials with HIL-214 or another candidate, HIL-216, in adults.

Norovirus is the leading cause of foodborne illness, resulting in vomiting and diarrhea, according to the Centers for Disease Control and Prevention (CDC). Outbreaks often occur when infected individuals come into direct contact with others, and the virus can also spread through contaminated food, water, and surfaces. Common sites for norovirus outbreaks include healthcare facilities, schools, and childcare centers. The virus poses a higher risk of severe infection for children under five, older adults, and immunocompromised individuals.

HilleVax had convinced investors of the significant market potential for its vaccine, estimating it to be worth billions of dollars. The company initially focused on obtaining approval for infant use but was also considering the adult market. The Phase 2b study, known as NEST-IN1, was a randomized, placebo-controlled trial involving over 3,000 healthy infants in the U.S. and Latin America. The results indicated that the vaccine's efficacy against moderate or severe acute gastroenteritis was a mere 5%, with 25 cases reported in the vaccine group and 26 in the placebo group.

Previously, HIL-214 had shown clinical benefits in adults. NEST-IN1 was the first efficacy study conducted in infants for a norovirus vaccine candidate. Rob Hershberg, CEO of HilleVax, stated that the appearance of multiple emerging GII.4 strains during the trial might have affected the vaccine's efficacy in infants. Despite this setback, the safety and immune response profile of HIL-214 remained consistent with prior testing.

HilleVax was established in 2021 through a collaboration between Takeda Pharmaceuticals and Frazier Healthcare Partners, with a license to what was then Takeda's norovirus vaccine candidate.