A Phase 3, Randomized, Double-Blind, Placebo-Controlled, Multicenter Study Evaluating the Efficacy and Safety of Favipiravir in Adult Subjects with Uncomplicated Influenza.

1. Understands the requirements of the study and provides written
informed consent prior to undergoing any study-related procedures.
2. Is an adult male or female between the ages of 18 and 80 years old,
inclusive (or according to national standards in each country).
3. Has 2 or more of the following symptoms (moderate to severe in intensity) at the time of enrollment that began 48 hours or less prior to the first dose of study medication:
a. Cough
b. Sore throat
c. Headache
d. Nasal congestion
e. Body aches and pains
f. Fatigue
4. Has a fever at the first visit or in the 6 hours prior if antipyretics were taken, defined as
a. >= 38.0°C (>= 100.4°F) for subjects < 65 years old; or
b. >= 37.8°C (>= 100.0°F) for subjects >= 65 years old.
5. Tests positive for influenza A or B during the 48 hours between onset of symptoms and anticipated dosing with study medication
a. Confirmed at the site by a Rapid Antigen Test (RAT) provided for the study or real time polymerase chain reaction (PCR) OR
b. Confirmed by diagnostic assay (e.g. non-study RAT or PCR) from another clinic.
OR
c. A subject testing negative by RAT may still be enrolled if the Medical Monitor and Investigator agree that there is a known influenza outbreak circulating in the community or the subject has been in close contact with a person who was recently confirmed to have influenza by RAT or another laboratory test.
6. If male, subject must:
a. Be sterile (e.g., have had a vasectomy at least 6 months prior to Day 1 dosing) OR
b. Agree he will not donate sperm during the study and for 3 months following the last dose of study medication, AND
c. Will strictly adhere to the following contraceptive measures during the study and for 3 months following the last dose of study medication:
i. Abstain from sexual intercourse OR
ii. Use a condom during sexual intercourse with a female of child-bearing potential. In addition, the female partner must use another form of contraception (e.g. intrauterine device [IUD], diaphragm with spermicide, oral contraceptives, injectable progesterone, or subdermal implants).
iii. The final decision of effective contraception will be made in accordance with local regulations.
7. If female, subject must:
a. Be unable to bear children (have not had a period for >=12 consecutive months, have had her uterus or ovaries removed, or have had a tubal ligation) OR
b. Have a male partner incapable of fathering a child (e.g., has had a vasectomy at least 6 months prior to study entry) OR
c. Have a negative pregnancy test at screening AND
d. Not have had unprotected sex within the last month or used a medically approved method of contraception within the last month AND
e. If she is of childbearing potential, will strictly adhere to the following contraceptive measures during the study and for 3 months following the last dose of study medication:
i. Abstain from sexual intercourse OR
ii. Her male partner agrees to use a condom during sexual intercourse AND
iii. Agree to use an approved method of contraception (e.g., IUD, diaphragm with spermicide, oral
contraceptives, injectable progesterone, or subdermal implants).
iv. The final decision of effective contraception will be made in accordance with local regulations.

1. Female subjects who are pregnant, currently breast-feeding, or have a positive pregnancy test at Screening.
2. Has taken an anti-influenza drug (e.g., amantadine hydrochloride, rimantadine, oseltamivir phosphate, zanamivir hydrate, peramivir or other) within 4 weeks prior to signing the informed consent.
3. Has received any live attenuated influenza vaccine within 4 weeks prior to signing the informed consent.
4. Has underlying chronic respiratory disease (e.g., chronic obstructive pulmonary disease [COPD], chronic bronchitis, diffuse panbronchiolitis, bronchiectasis, pulmonary emphysema,
pulmonary fibrosis, or active tuberculosis). Subjects with bronchial asthma will be excluded from the study if they presently experience asthma symptoms, are currently requiring treatment, or have had an asthma attack in the past year.
5. At the beginning of the study, is suspected of having bacterial respiratory infection (i.e., expectoration of purulent or mucopurulent sputum and/or infiltrate in lung observed on chest
x-ray, or is on antibiotics for pulmonary disease).
6. Has a history of gout or is under treatment for gout or hyperuricemia.
7. Has hereditary xanthinuria.
8. Has a history of hypouricemia (under 1 mg/dL) or xanthine calculi of the urinary tract.
9. Has a history of hypersensitivity to an anti-viral nucleosideanalog drug targeting a viral RNA polymerase.
10. Is using adrenocorticosteroids (except topical preparation) or immunosuppressive drugs (e.g., immunosuppressants, anticancer drugs).
11. Has an allergy to acetaminophen (paracetamol) or has a contraindication for acetaminophen (paracetamol).
12. Has a serious chronic disease (e.g., human immunodeficiency virus [HIV], cancer requiring chemotherapy within the preceding 6 months, moderate or severe hepatic insufficiency
and/or unstable renal, cardiac, pulmonary, neurologic, vascular, or endocrinologic disease states requiring medication dose adjustments within the last 30 days).
13. Has previously received favipiravir (T-705a).
14. Has renal insufficiency requiring hemodialysis or continuous ambulatory peritoneal dialysis (CAPD).
15. Has a history of alcohol or drug abuse in the preceding 2 years.
16. Has a psychiatric disease that is not well controlled (not on a stable regimen for greater than one year).
17. Has taken another investigational drug within 30 days prior to signing the informed consent.
18. Is deemed by the Investigator to be ineligible for any reason.
19. Is employed by or is related to an employee of the clinical study site.