Dose-Finding Study of Favipiravir in the Treatment of Uncomplicated Influenza

This is a Phase 2, randomized, double-blind, placebo-controlled, multicenter study designed to evaluate the efficacy and safety of a 5-day regimen of favipiravir in influenza patients aged 20-80 years. Enrolled patients will be randomly assigned to 1 of 3 parallel treatment dose groups:Placebo; Low-dose favipiravir (1000 mg favipiravir BID for 1 day, followed by 400 mg favipiravir BID for 4 days); High-dose favipiravir (1200 mg favipiravir BID for 1 day, followed by 800 mg favipiravir BID for 4 days).

Inclusion criteria

• Patients who test positive for influenza A or B by a commercially available Rapid Antigen Test (RAT) of the nasopharynx. A patient with a negative RAT result may still enroll if the sponsor and investigator agree that there is a known influenza outbreak circulating in the community.
• Patients ≥ 20 but < 65 years of age with a temperature (oral) of 100.4°F (38.0°C) or more; patients ≥ 65 years of age with a temperature (oral) of 100.0°F (37.8°C) or more at the first visit, or in the 6 hours prior if antipyretics were taken.
• Patients with 2 or more of the following symptoms (moderate to severe in intensity) at the time of enrollment:

• Cough
• Sore throat
• Headache
• Nasal congestion
• Feeling feverish
• Body aches and pains
• Fatigue (tiredness)

Exclusion criteria

• Patients who have had influenza symptoms or fever (i.e., one of the symptoms listed under the inclusion criteria) for 36 hours or more prior to study screening.
• Patients who have underlying chronic respiratory disease (e.g., chronic obstructive pulmonary disease [COPD], chronic bronchitis, diffuse panbronchiolitis, bronchiectasis, pulmonary emphysema, pulmonary fibrosis, bronchial asthma, or old tuberculosis).
• Patients who at the beginning of the study are suspected of having bacterial respiratory infection (i.e., expectoration of purulent or mucopurulent sputum and/or infiltrate in lung in a chest x-ray, etc.).
• Patients who have serious chronic diseases. For example, patients with HIV, cancer (i.e., requiring chemotherapy within the preceding 6 months), cirrhosis (end-stage), and/or unstable renal, cardiac, pulmonary, neurologic, vascular, or endocrinologic disease states requiring medication dose adjustments within the last 30 days.