HilleVax, Inc. (NASDAQ:HLVX), a clinical-stage biopharmaceutical company focused on developing and commercializing novel vaccines, today reported results from a prespecified immunogenicity analysis of the 203 subjects enrolled in the run-in cohort of NEST-IN1 (Norovirus Efficacy and Safety Trial for INfants), the company's ongoing Phase 2b trial for HIL-214, its investigational virus-like particle (VLP) based vaccine candidate for the prevention of moderate-to-severe norovirus-related acute gastroenteritis (AGE) in infants. These results follow the previously announced positive recommendation from an independent safety data monitoring committee based on this same cohort.

Immunogenicity Results:

• Geometric Mean Titers (GMTs) of pan-IG antibodies 28 days following the second dose were 11,102.0 IU/mL and 2,185.5 IU/mL for GI.1 and GII.4, respectively, for HIL-214 compared to 59.6 IU/mL and 73.5 IU/mL for GI.1 and GII.4, respectively, for placebo. These titers corresponded to a Geometric Mean Fold Rise (GMFR) versus baseline of more than 18-fold for HIL-214.
• Seroresponse rates (SRRs) for HIL-214, defined in NOR-212 as the percentage of subjects with at least a 4-fold increase in pan-Ig (immunoglobulin) antibody titers 28 days following the second dose compared to pre-vaccination baseline, were 99.0% for GI.1 and 86.9% for GII.4. SRRs for placebo were 4.1% and 3.1% for GI.1 and GII.4, respectively.

"We are very pleased with the immunogenicity results from the NEST-IN1 run-in cohort which were consistent with our expectations based on previous studies of HIL-214 given to infants," said Rob Hershberg, MD, PhD, Chairman and Chief Executive Officer of HilleVax. "We now look forward to the full NEST-IN1 topline safety and efficacy data which remain on-track for the second half of 2023."

NEST-IN1 is a Phase 2b, randomized, double-blind, placebo-controlled clinical trial to evaluate the efficacy, safety, and immunogenicity of HIL-214 in infants of approximately 5 months of age at time of initial vaccination at sites in the United States and Latin America. The study is planned to enroll 3,000 subjects who will be randomized 1:1 to receive a two-dose regimen of either HIL-214 or placebo. The clinical trial protocol includes the now completed prespecified 200 subject run-in to assess safety and immunogenicity. The primary objective of the trial is to evaluate the protective efficacy of HIL-214 against the first confirmed moderate or severe AGE event due to a HIL-214 vaccine strain, GI.1 or GII.4, (excluding certain co-infections) that occurs prior to each subject reaching 12 months of age. A key secondary endpoint is to evaluate the protective efficacy of HIL-214 against any GI or GII norovirus strain.