A Study to Evaluate the Safety and Efficacy of XC221 in Patients With Uncomplicated Influenza or Other Acute Viral Upper Respiratory Infections

Inclusion Criteria:

1. Men and women between the ages of 18 and 65 years inclusive;
2. Presence of written consent to participate in the study in accordance with applicablelaw;
3. Clinical signs of mild to moderate influenza or other acute respiratory infections (ARIs): an increase in body temperature, measured at the axilla, with a value between 38.0 °C and 39.5 °C, inclusive, during the current illness and without takingantipyretics within the last 8 h at the time of screening; at least one respiratorymanifestation of influenza or other ARI (cough, runny nose/ stuffy nose, sore throat)of at least 2 points on a 4-point scale; at least one systemic manifestation ofinfluenza or other ARI (headache, muscle pain, chills/sweating, fatigue) of at least 2points on a 4-point scale.
4. No indication for hospitalization at the time of enrollment in the study;
5. Duration of illness from manifestation of symptoms to the first dose of studydrug/placebo not more than 48 hours;
6. Negative pregnancy test for women of preserved reproductive potential;
7. Consent to use adequate contraceptive methods throughout the study and for 30 daysafter study completion;
8. Ability to understand the requirements for study participants, to give written consentto participate in the study (including the use and communication of patient healthinformation relevant to the study) and to comply with the procedures of the studyprotocol.

Exclusion Criteria:

1. Pregnant and breastfeeding women;
2. Known hypersensitivity to the study drug, including the active and/or excipients.
3. Lactase deficiency, lactose intolerance, glucose-galactose malabsorption, galactoseintolerance;
4. Diagnosis of COVID-19 established or probable at present (based on examination andanalysis of epidemiological history);
5. Positive result of rapid test for SARS-CoV-2;
6. Blood oxygen saturation (SpO2) ≤ 95%, respiratory rate ≥ 22/min.
7. Complicated course of influenza or other acute respiratory infections;
8. Participation in any other clinical trial within 90 days prior to the screeningperiod;
9. Known (based on medical history) or suspected alcohol abuse, psychotropic drugs, drugdependence, drug addiction;
10. Presence of mental illness, including a history of mental illness;
11. Clinical suspicion of pneumonia or other bacterial infections (including sinusitis,otitis media, urinary tract infection, meningitis, sepsis, etc.) requiringprescription of antibacterial drugs;
12. Taking antibiotics, antivirals, or immunomodulatory drugs for < 48 h before the studyand/or plans to use these groups of drugs (other than the study drug) during thestudy;
13. Use of systemic, inhaled, or nasal glucocorticosteroids within 30 days prior to thestudy and/or plans to use glucocorticosteroids (except topical cutaneous agents)during the study;
14. Failure to withdraw for the duration of the study other medications that may affectthe outcome of this study, such as antiviral medications, or medications that areincompatible with the study therapy;
15. Any cardiovascular, renal, hepatic, gastrointestinal, endocrine or nervous systemdiseases, severe decompensated chronic (including chronic kidney disease and chronicliver disease) or acute diseases or any other condition/disease that, in the opinionof the investigator, would make it unsafe for the patient to participate in the study;
16. Any vaccination of the patient within 90 days prior to inclusion in the study;
17. Diabetes mellitus in decompensation;
18. Obesity of 2-3 degrees (body mass index of 35 kg/m2 or more).
19. Patients who have undergone surgery within 30 days prior to the Screening Visit andpatients who are scheduled to undergo surgery, including diagnostic procedures, or ahospital stay during the study;
20. The presence of cancer, including a history of cancer (with the exception of a curedtumor with sustained remission for more than 5 years);
21. The presence of HIV infection, tuberculosis, including in the anamnesis;
22. Meningeal syndrome;
23. Disturbance of consciousness (in the form of stunting, soporus, delirium, delirium,etc.).
24. Symptoms of pneumonia and possible acute respiratory distress syndrome (ARDS): coughwith foaming sputum with blood, shortening of the pulmonary sound on percussion, alarge number of different-caliber wet rales and abundant crepitation on auscultation,a sharp drop in blood pressure, deafness of heart tones and arrhythmia;
25. Patient's refusal to use approved contraception or to completely abstain from sexualintercourse for the duration of study participation, beginning at Visit 1, and for 30days after completion of study participation;
26. Other reasons that, in the opinion of the investigator, prevent the patient fromparticipating in the study or create an unreasonable risk. Withdrawal Criteria:
27. Patient's desire to stop participating in the study (withdrawal of informed consent).Each patient has the right to stop participating in the study at any time withoutgiving a reason. Withdrawal from the study will not affect the medical care providedto the patient in the future.
28. The decision by the research physician that the patient should be excluded is in thepatient's own interest;
29. The need to prescribe etiotropic or any other treatment prohibited in the study, asdetermined by the investigating physician.
30. Patient refuses to cooperate with the investigator or is undisciplined;
31. Causes/occurrence during the study of situations that threaten patient safety (e.g.,hypersensitivity reactions, serious adverse events, etc.);
32. Inclusion of a patient in the study with inclusion/inclusion criteria not met (priorto randomization);
33. Significant treatment failure; Significant failure is defined as a) skipping studydrug/placebo for 2 consecutive days or more or b) taking, in total, < 80% or > 120% ofthe full course (full course = 10 pills).
34. Positive pregnancy test;
35. A confirmed diagnosis of COVID-19;
36. Occurrence in the course of the study of other reasons that prevent the studyaccording to the protocol.
37. Death of a patient.