A Study to Evaluate INT101 in Healthy Adults for the Prevention of Norovirus Gastroenteritis

This is a single-center, single-blind, randomized, dose-escalation, placebo-controlled, multiple-dose, Phase 1 clinical trial designed to evaluate the safety and immunogenicity of INT101 intramuscular injection in healthy adults. INT101 is a vaccine candidate containing multivalent norovirus antigens (genotypes GII.3, GII.4, and GII.17), formulated at 20 μg per antigen (60 μg total) per 0.5 mL vial. The matching placebo is identical in formulation and appearance, excluding the active norovirus antigens. Approximately 30 participants will be enrolled into two dose groups: a low-dose group (30 μg/0.25 mL) and a high-dose group (60 μg/0.5 mL). Each dose group consists of a sentinel cohort followed by a main cohort. Within each cohort, participants are randomized in a 2:1 ratio to receive either INT101 or placebo. Enrollment proceeds in a staggered, dose-escalation manner: Sentinel A (low dose) is dosed first, followed by a Day 7 DSMB safety review before proceeding to Cohort A. DSMB (Data and Safety Monitoring Board) evaluations are conducted at Day 7 after the first and third (last) doses within Cohort A before advancing to the high-dose groups (Sentinel B and Cohort B). Each participant receives 3 intramuscular injections (into the deltoid muscle) at 4-week intervals (Visit 2/Baseline, Visit 4, Visit 6). The study includes a screening period (up to 4 weeks), a treatment period (8 weeks, 3 doses), and a follow-up period of approximately 6 months after the last dose, for a total of 9 study visits. Safety endpoints include immediate adverse events, solicited local and systemic adverse events, unsolicited adverse events, serious adverse events, and clinically significant changes in laboratory tests, physical examinations, and vital signs. Immunogenicity endpoints include seroconversion rate, geometric mean titer (GMT), and geometric mean ratio (GMR) of norovirus antibodies, assessed at Days 7, 28, 35, 56, 63, 84, and 224 relative to baseline.

Inclusion criteria

• Healthy adults aged 19 to 48 years (inclusive) as of the screening visit
• Body Mass Index (BMI) of 18.0 to 30.0 kg/m^2 (inclusive) at screening
• Women and men of reproductive potential willing to use a highly effective contraceptive method (hormonal contraceptives, intrauterine device/system, or sterilization) from 30 days prior to the first investigational product administration through 2 months after the last administration
• For female participants, a negative pregnancy test result at screening
• Agreement not to donate blood or receive blood transfusion during the study period
• Judged to be healthy by the investigator based on clinical judgment, medical history, and physical examination at screening
• Able to understand the purpose of the study and voluntarily provide written informed consent to participate and comply with study restrictions

Exclusion criteria

• Autoimmune disease (e.g., rheumatoid arthritis, hypothyroidism) at screening
• Uncontrolled hypertension (BP not controlled below 140/90 mmHg, or 130/80 mmHg if diabetic, despite maximal doses of 3 or more antihypertensive agents) or diabetes (HbA1c >7.0%)
• Neurological disease (e.g., epilepsy, seizure, Guillain-Barre syndrome)
• Asthma
• Uncontrolled bleeding disorder or receipt of anticoagulant therapy
• History of immunodeficiency or immune dysfunction
• History of malignancy within 5 years prior to the first dose (excised skin lesions or basal cell carcinoma successfully treated with no recurrence for 3 or more years may be enrolled at investigator discretion)
• Suspected or history of substance abuse prior to study participation
• Significant alcohol consumption (21 or more drinks/week for men, 14 or more drinks/week for women) or excessive smoking (20 or more cigarettes/day) within 1 month prior to the first dose
• History of gastrointestinal illness (e.g., enteritis, diarrhea, abdominal pain, vomiting) within 14 days prior to the first dose
• Positive result for HIV antigen/antibody, Hepatitis B surface Antigen (HBsAg), Anti-Hepatitis C Virus (Anti-HCV), or syphilis at screening
• Participation in another clinical trial involving an investigational drug or device within 6 months prior to the first dose
• Receipt of immunoglobulin or blood products within 6 months prior to the first dose, or planned receipt during the study
• Receipt of immunosuppressive or immunomodulatory agents (e.g., Azathioprine, Cyclosporine) within 6 months prior to the first dose
• Receipt of cytotoxic chemotherapy that may affect immune function
• History of radiation therapy
• Receipt or planned receipt of any vaccine other than the investigational product within 4 weeks before or after each investigational product administration
• High fever (38C or above) within 3 days prior to the first dose, or clinically significant suspected acute infection
• Use of analgesics or antipyretics within 1 day prior to investigational product administration
• Chronic steroid use (Prednisolone more than 10 mg/day for more than 14 consecutive days), unless discontinued for 6 months or more prior to screening (topical, nasal, inhaled, or ophthalmic steroids permitted regardless of dose)
• Inflammation at or near the planned injection site
• Planned blood donation during the study period
• Pregnant or breastfeeding women
• History of serious adverse event, allergy, or hypersensitivity reaction related to vaccination
• History of organ or hematopoietic stem cell transplant prior to study participation
• Clinically significant abnormal laboratory test result at screening
• Suspected or history of alcohol abuse
• Known hypersensitivity to the investigational product or its components
• Chronic underlying disease, congenital disease, or mental illness judged by the investigator to interfere with study conduct or completion
• Any other condition judged by the investigator to make the participant unsuitable for the study