Inclusion Criteria:
1. Voluntarily and personally signed Informed Consent Form (ICF) by a participant obtained prior to the conduct of any study-related procedure;
2. Males and females aged 18 to 65 years (inclusive) at the time of signing the ICF;
3. Subjects with influenza or other acute respiratory viral infections confirmed by polymerase chain reaction (PCR);
4. Presence of clinically significant signs of influenza or acute respiratory viral infections at screening:
* Body temperature \>38,0 °С at randomization, with no intake NSAID within 12 hours before randomization;
* Presence of at least two of the following symptoms of influenza or other acute respiratory viral infections (cough, rhinorrhea, sore throat, or a throat irritation) each rated non less than 6 points on a numeric rating scale (NRS);
* Presence of at least one of the following systemic manifestations of influenza or other acute respiratory viral infections (headache, myalgia, or general weakness) rated non less than 6 points on a numeric rating scale (NRS).
5. Duration of illness from symptoms onset to administration of the first dose of investigational medical product or comparator is ≤ 48 hours;
6. No clinical indications for hospitalization at the time of study enrollment;
7. Consent to use adequate contraceptive methods throughout the study and for 30 days after study completion. The follwing subjects are eligible for inclusion in the study:
* Females of childbearing potential must have a negative pregnancy test and use one of the folliwing adequate contraceptive methods: sexual abstinence, condom combined with spermicide or hormonal contraceptives, contraceptive subdermal implant, intrauterine hormonal system, intrauterine device. Females not of childbearing potential (i.e., with a history of hysterectomy, bilateral oophorectomy, bilateral tubal ligation, comfirmed infertility, or ≥ 2 of menopause) are also eligible for participation;
* Males with reptoductive potential must use one of the folliwing adequate contraceptive methods: sexual abstinence, condom combined with spermicide or hormonal contraceptives. Males with infertility or a history of vasectomy are also eligible for participation;
Exclusion Criteria:
1. Clinically significant allergic history;
2. Hypersensitivity to active substances of medical produtcs Ingavirin and Ingavirin forte, and/or to any excipient contaned in the investigational medicinal product or comparator;
3. Intolerance to active substances of medical produtcs Ingavirin and Ingavirin forte, and/or to any excipient contaned in the investigational medicinal product or comparator;
4. Known galactose intolerance, lactase deficiency, or glucose-galactose malabsorption;
5. Clinical suspicion of pneumonia of any etiology, or other bacterial infection (e.g. sinusitis, otitis media, urinary tract infection, meningitis, sepsis) requiring initiation for antibacterial therapy;
6. Nasal obstruction due to structural pathology, such as sequelae of nasal trauma, nasal polyps, septal deviation, or other organic causes;
7. History of vasomotor rhinitis;
8. Administration of antibiotics, antiviral (including Ingavirin), or immunomodulatory agents within 48 hours prior to study, and/or anticipated need for any of these agents during the study;
9. Vaccination within 90 days prior to study enrollment;
10. Uncontrolled diabetes mellitus;
11. Obesity, class II or III (body mass index ≥35 kg/m²);
12. Pregnancy or lactation;
13. Positive test for SARS-CoV-2 at screening;
14. History of autoimmune diseases;
15. Current or past HIV, syphilis, hepatitis B and/or C, or tuberculosis;
16. Known or suspected history of alcohol, psychotropic drug, or substance abuse or dependence;
17. History of chronic respiratory disease, including but not limited to: chronic obstructive pulmonary disease (COPD), asthma, chronic bronchitis, diffuse panbronchiolitis, pulmonary emphysema, or pulmonary fibrosis;
18. Chronic heart failure, New York Heart Association (NYHA) functional class III or IV;
19. Current or past psychiatric disoder;
20. Any clinically significant cardiovascular, renal, hepatic, gastrointestinal , endocrine, or neurological disoder, including severe uncompensated chronic conditions (e.g., chronic kidney disease, chronic liver disease) or acute illness, or any other medical or psychiatric condition that, in investigator's opinion, could pose a safety risk to the subject if they participate in the study;
21. Subject's refusal to use an adequate method of contraception or to practice continuous sexual abstinence throughout the study and for 30 days after study completion;
22. Participation in another clinical trial within 3 months prior to screening;
23. Other conditions which, in the judgment of the investigator, could compromise the subject's participation in the study or pose an undue risk.
Exclusion Criteria:
1. Subject's decision to withdraw from the study (withdrawal of informed consent);
2. Investigator's decision to discontinue the subject from the study in the subject's best interest;
3. Investigator-determined need for a concomitant therapy explicitly prohibited by the protocol of clinical study;
4. Subject's use of a therapy prohibited by the protocol;
5. Positive urine test for beta-human chorionic gonadotropin (β-hCG) in females of childbearing potential;
6. Lack of adequate cooperation by the subject with the investigator during the study;
7. Emergence during the study of conditions or events that jeopardize subject safety (e.g., hypersensitivity reactions, serious adverse events \[SAEs\]) or, in the investigator's medical judgment, worsen the subject's prognosis or preclude further participation in the clinical study;
8. Incorrect inclusion of a subject who does not meet the protocol-specified inclusion and/or exclusion criteria;
9. Major deviation from the treatment regimen, defined as:
* Missing two or more consecutive doses of the investigational medicinal product (IMP) or comparator;
* Total intake of fewer than 80% or more than 120% of the planned total number of capsules (full course includes 10 capsules);
10. Confirmed diagnosis of COVID-19;
11. Occurrence during the study of any other condition that precludes adherence to the protocol;
12. Subject's death.
