Shares of vaccine-developer HilleVax Inc ( HLVX ) are down on Monday on a session volume of over 7 million as per data from Benzinga Pro.

Monday, the company released topline data results from the NEST-IN1 Phase 2b randomized, double-blind, placebo-controlled trial of the efficacy, safety, and immunogenicity of HIL-214 in infants approximately five months of age at the time of initial vaccination.

HIL-214 is the company’s investigational virus-like particle (VLP) based vaccine to prevent moderate-to-severe norovirus-related acute gastroenteritis.

Norovirus, also called the “winter vomiting bug,” is a stomach bug that causes vomiting and diarrhea.

In the NEST-IN1 study, there were 51 primary endpoint events, with 25 in the vaccine arm (n=1,425) and 26 in the placebo arm (n=1,399), resulting in a vaccine efficacy of 5%.

The study did not meet its primary endpoint of efficacy against moderate or severe acute gastroenteritis (AGE) events due to GI.1 or GII.4 norovirus genotypes.

No clinical benefit was observed across secondary endpoints.

HIL-214 exhibited a safety and immunogenicity profile consistent with what was observed in the prespecified analysis of the first 200 subjects in NEST-IN1 and in previously reported studies.

“We are disappointed that the NEST-IN1 study did not meet its primary efficacy endpoint,” said Rob Hershberg, Chairman and Chief Executive Officer of HilleVax ( HLVX ). “While HIL-214 previously showed clinical benefit in adults, NEST-IN1 was the first efficacy study conducted in infants for a norovirus vaccine candidate. We believe the efficacy in the infant setting may have been impacted by the appearance of multiple emerging GII.4 strains in this trial.”

The company plans to discontinue further development of HIL-214 in infants and is exploring the potential for continued development of HIL-214 and HIL-216, HilleVax’s Phase 1 ready vaccine candidate, in adults.

Price Action: HLVX shares are down 86.3% at $1.93 at last check Monday.

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