Dose Range Study to Evaluate the Efficacy and Safety of AV5080 in Patients With Influenza

Inclusion Criteria: 1. Signed informed consent; 2. Males and females between 18 and 65 years old (inclusive); 3. Outpatients and those hospitalized for epidemiological reasons with mild and moderate severity diagnosed influenza (ICD 10: J10 Influenza caused by an identified influenza virus) without complications; The severity of influenza is defined under the Influenza in the Influenza in Adults Clinical Guidelines of the National Scientific Society of the Infectious Diseases Specialists; 4. Positive enzyme-linked immunosorbent assay for influenza virus at screening; 5. At least one episode of an increased body temperature up to 38°C and above within 48 hours before screening; 6. The presence of at least one of the following symptoms of moderate severity on screening: Headache, weakness/malaise, myalgia/muscle ache, hot flash/chills; 7. Duration of the disease not exceeding 48 hours (according to the patient) on screening; 8. Consent of patients to use adequate contraception methods throughout the study. Adequate contraception methods include: * Oral contraceptives or contraceptive patches; * Condoms or diaphragms (barrier method) with spermicide; or * An intrauterine device. Exclusion Criteria: 1. Pregnant or breastfeeding women or women planning to become pregnant during the clinical study; women of child-bearing potential (including women in their post-menopausal period for less than two years) who do not use adequate contraception measures; 2. Individual intolerance of the AV5080 drug or its components; 3. Lactase deficiency, lactose intolerance, glucose-galactose malabsorption; 4. Influenza complications, signs of a bacterial infection or severe disease course at the screening (based on the criteria specified in the Influenza in Adults Clinical Guidelines of the National Scientific Society of Infectious Diseases Specialists, 2014); 5. The history of anti-influenza immunization within 12 months before the screening; 6. Participation in other clinical studies within three months before screening; 7. Chronic respiratory system diseases (asthma, COPD); 8. Administration of neuraminidase inhibitors (zanamivir, oseltamivir), immunomodulators, systemic glucocorticoids, and antibiotics within one month before screening; 9. HIV infection, chronic hepatitis С or hepatitis B infection (according to the patient's history); 10. Significant cardiovascular diseases at present or within 12 months prior to screening including: class III or IV chronic heart failure (as defined by NYHA), severe arrhythmia requiring administration of class Ia, Ib, Ic or III anti-arrhythmic drugs, non-stable angina, myocardial infarction, previous surgery on the heart and coronary vessels, significant heart valves diseases, transient ischemic attack or stroke, uncontrollable hypertension with systolic BP \> 180 mmHg and diastolic BP \> 110 mmHg, pulmonary embolism or deep vein thrombosis; 11. Chronic alcohol abuse, drug abuse or addiction to the other chemicals in history; 12. Inability to read or write; unwillingness to understand and comply with the Protocol procedures; non-compliance with the drug dosing regimen or procedures which, in the Investigator's opinion, may affect the study results or the patient's safety and prevent the patient to participate in the study; any other concomitant diseases or severe mental disorders, which make the patient ineligible to participate in the study, limit the legal basis for Informed Consent procedure, or may affect the patient's ability to participate in the study.