A Study to Evaluate the Efficacy, Safety and Pharmacokinetics of CDI-988 in Healthy Adults After Challenge With Snow Mountain Virus

Inclusion Criteria: * Healthy male or non-pregnant female * Aged 18 to 49 years * Good state of health * Known fucosyl transferase 2 (FUT2) secretor status Exclusion Criteria: * History of participation in any norovirus challenge or vaccine clinical trial * Receipt or planned receipt of any non-live vaccines within 7 days or live vaccines within 30 days before screening or prior to Day 28 * History of suspected norovirus gastroenteritis or chronic/recurrent gastrointestinal symptoms (e.g., diarrhea or vomiting) within 2 years prior to screening * History of diagnosed gastrointestinal malabsorption disorders, major gastrointestinal surgery, or diagnosed chronic GI conditions * Presence of moderate or severe illness, fever (≥38°C), or diarrhea/vomiting within 7 days prior to challenge * Any acute illness on Day 1 (dosing day) * Positive Day 0 stool tests for enteric pathogens * Body weight \<45 kg or BMI \<18 or \>32 kg/m² on Day 0 * Use of immunosuppressive therapy within 6 months prior to Day 0 or having any primary or secondary immunocompromising condition * Use of high-dose systemic corticosteroids (≥20 mg/day prednisolone for ≥2 weeks) or high-dose inhaled steroids for \>7 days within 6 months