A Study of S-033188 (Baloxavir Marboxil) Compared With Placebo or Oseltamivir in Otherwise Healthy Patients With Influenza

Inclusion Criteria

• Patients who are able to understand the study and comply with all study procedures, and willing to provide written informed consent/assent prior to the predose examinations appropriately. As for adolescent patients, informed consent/assent of voluntary participation should be obtained in accordance with local requirements
• Male or female patients aged ≥ 12 to ≤ 64 years at the time of signing the informed consent/assent form.
• Patients with a diagnosis of influenza virus infection confirmed by all of the following:
• Fever ≥ 38ºC (axillary) in the predose examinations or > 4 hours after dosing of antipyretics if they were taken
• At least one of the following general systemic symptoms associated with influenza are present with a severity of moderate or greater
• Headache
• Feverishness or chills
• Muscle or joint pain
• Fatigue
• At least one of the following respiratory symptoms associated with influenza are present with a severity of moderate or greater
• Cough
• Sore throat
• Nasal congestion
• The time interval between the onset of symptoms and the predose examinations is 48 hours or less. The onset of symptoms is defined as either:
• Time of the first increase in body temperature (an increase of at least 1ºC from normal body temperature)
• Time when the patient experiences at least one general or respiratory symptom
• Women of childbearing potential who agree to use a highly effective method of contraception for 3 months after the first dose of study drug

Exclusion Criteria

• Patients with severe influenza virus infection requiring inpatient treatment.
• Patients aged ≥ 20 years with known allergy to oseltamivir (Tamiflu®).
• Patients with any of the following risk factors
• Women who are pregnant or within 2 weeks post-partum
• Residents of long-term care facilities (eg, welfare facilities for the elderly, nursing homes)
• Chronic respiratory diseases including bronchial asthma
• Neurological and neurodevelopmental disorders including disorders of the brain, spinal cord, peripheral nerve, and muscle (eg, cerebral palsy, epilepsy [seizure disorders], stroke, intellectual disability, moderate to severe developmental delay, muscular dystrophy, or spinal cord injury)
• Heart disease (such as congenital heart disease, congestive heart failure, or coronary artery disease), excluding hypertension without any other heart-related symptoms)
• American Indians and Alaskan natives
• Blood disorders (such as sickle cell disease)
• Endocrine disorders (including diabetes mellitus)
• Kidney disorders
• Liver disorders
• Metabolic disorders
• Compromised immune system (including patients receiving immunosuppressant therapy, or those with cancer or human immunodeficiency virus [HIV] infection)
• Morbid obesity (body mass index [BMI] ≥ 40)
• Patients unable to swallow tablets or capsules.
• Patients who have previously received Baloxavir Marboxil.
• Patients weighing < 40 kg
• Patients who have been exposed to an investigational drug within 30 days prior to the predose examinations.
• Women who are breastfeeding or have a positive pregnancy test in the predose examinations. The following female patients who have documentation of either a or b below do not need to undergo a pregnancy test in the predose examinations:
• Postmenopausal (defined as cessation of regular menstrual periods for 2 years or more and confirmed by a follicle-stimulating hormone test) women
• Women who are surgically sterile by hysterectomy, bilateral oophorectomy, or tubal ligation
• Patients with concurrent infections requiring systemic antimicrobial and/or antiviral therapy at the predose examinations.
• Patients who have received peramivir, laninamivir, oseltamivir, zanamivir, rimantadine, umifenovir, or amantadine within 30 days prior to the predose examinations.
• Patients who have received an investigational monoclonal antibody for a viral disease in the last year.
• Patients with sev