Acute upper and lower respiratory infections are a major public health problem and a leading cause of morbidity and mortality worldwide. The purpose of this trial is to assess the safety of the investigational agent INNA-051, given intranasally, and its potential effectiveness in reducing the occurrence, severity, and/or the duration of illness resulting from respiratory virus infections. The trial will enroll generally healthy adults (age 18 - 45 years) who are at risk for exposure to viral respiratory infection, for example, due to living conditions or occupation. Participants will be treated with INNA-051 or placebo once weekly for 4 weeks (Part A) or 12 weeks (Part B) during the respiratory virus season.

Viral respiratory infections are associated with significant morbidity and mortality. The diversity of viruses, along with their propensity for mutation, ignited an interest in host-directed therapies that are effective across a wide range of viral pathogens. Toll-like receptors (TLRs) are potential targets for the development of such agents given their central role in host immune defenses.

INNA-051, a TLR2/6 agonist, is being developed as an intranasal innate immune-boosting prophylactic approach for individuals at risk for symptoms and/or complications resulting from respiratory viral infections due to age, occupation, and/or co-morbidities.

This randomized, double-blind, two-part, placebo-controlled, multicenter, Phase 2a trial is designed to evaluate the safety, tolerability, and efficacy of INNA-051 in generally healthy adult participants (age 18 to 45 years, inclusive) who are at increased risk for exposure to viral respiratory infections.

The primary purpose of Part A of the trial is to assess the safety and tolerability of INNA-051 (bilateral intranasal dry powder) in an outpatient setting compared with placebo. In part A of the trial, INNA-051 will be self-administered once weekly for 4 weeks in an outpatient setting during the respiratory virus season.

The purpose of Part B of the trial is to measure the safety, tolerability, and efficacy of INNA-051 bilateral intranasal dry powder compared with placebo in the prevention of symptomatic clinical illness due to RT-qPCR-confirmed viral respiratory infections. In part B of the trial, INNA-051 will be self-administered once weekly for 12 weeks during the North American respiratory virus season.

Inclusion Criteria:

• In good general health and without clinically significant medical, psychiatric, chronic or intermittent health conditions.
• At risk for exposure to viral respiratory infection, for example, living in crowded housing, university housing, or military barracks, working in a childcare center or caring for a child aged 10 or less, healthcare workers, factory workers, taxi and bus drivers, grocery clerks, and educators or counselors who work in crowded environments or with multiple exposures with different people daily.
• Agree to use highly effective birth control.

Exclusion Criteria:

• Presence of Type I or Type II diabetes, asthma or other chronic respiratory condition.
• Active infections including Hepatitis B Virus, Hepatitis C Virus, or Human Immunodeficiency (HIV).
• Concurrent participation in another clinical trial involving investigational product or prior receipt of investigational product within 90 days or 5 half-lives of the product.
• Active clinical signs or symptoms of acute respiratory illness (runny nose, sore throat, fever, etc.).
• Received a vaccine against Respiratory Syncytial Virus (RSV) or COVID-19 within 180 days.
• Pregnant or lactating women.