Efficacy and Safety of XC8, Film-coated Tablets, 40 mg in Patients With Dry Non-productive Cough Against Acute Respiratory Viral Infection

Inclusion Criteria:

1. Signing and dating of the IPP informed consent form by the patient.
2. Women and men between the ages of 18 and 65 years, inclusive, at the time of signingthe informed consent form.
3. Clinical diagnosis of acute respiratory viral infection of the upper respiratory tract (ICD-10 code J00-J06) or acute bronchitis (J20, J21 according to ICD-10).
4. Onset of disease symptoms no more than 3 days prior to screening.
5. Presence of a patient with a dry unproductive cough.
6. Frequency of cough episodes ≥10 in the past 24 h before the screening visit andrandomization.
7. Cough frequency rated by the patient as 3-4 on the daytime cough section and 2-4 onthe nighttime cough section of the Daytime and Nighttime Cough Scales.
8. Patient rating of cough severity on the DRS ≥ 4 points.
9. No indication for therapy due to BHSA infection at the time of study inclusion:negative rapid test for Group A β-haemolytic streptococcus.
10. For women of preserved reproductive potential, a negative pregnancy test and agreementto use approved contraceptive methods for the duration of study participation,beginning at visit 0, and for 3 weeks after the end of the study; for men, agreementto use approved contraceptive methods throughout the study participation period andfor 3 weeks after the end of the study.

Exclusion Criteria:

1. Known or suspected hypersensitivity to the active ingredient or any of the excipientsof the study drug/placebo.
2. Known or suspected hypersensitivity to acetylcysteine.
3. Lactose intolerance, lactase deficiency, glucose-galactose malabsorption.
4. Trauma (including open wounds in the mouth and erosive-desquamous lesions of the oralmucosa) and/or oropharyngeal burns, scarlet fever, rubella, measles, mumps at the timeof screening or within 3 months prior to screening.
5. Acute obstructive laryngitis or suspected obstructive laryngitis.
6. Presence of signs of laryngeal stenosis (stridor, shortness of breath).
7. Exacerbation of chronic bronchitis or chronic obstructive pulmonary disease (COPD).
8. Bronchial asthma, including a history.
9. History of tuberculosis.
10. History of pulmonary emphysema.
11. Acute or chronic pneumonia, or suspected pneumonia.
12. Condition after intubation.
13. Gastroesophageal reflux being the primary cause of cough (as judged by theinvestigating physician).
14. Allergic rhinitis as primary cause of cough (according to study physician).
15. Body temperature > 39.0 °C.
16. Presence of at least one of the epidemic signs: return from a foreign trip 14 daysprior to the onset of symptoms; presence of close contact in the past 14 days with aperson under COVID-19 surveillance who has subsequently become ill; having closecontact in the past 14 days with a person who has a laboratory-confirmed diagnosis ofCOVID-19; having occupational contacts with an individual with a suspected orconfirmed case of COVID-19.
17. Positive result of laboratory testing for SARS-CoV-2 RNA using nucleic acidamplification techniques or SARS-CoV-2 antigen using immunochromatographic analysis atthe time of screening.
18. The need for systemic antibiotic therapy and/or other drugs/procedures from the listof prohibited therapies/procedures.
19. Use of analgesics or antipyretics within 12 hours prior to screening.
20. Use of glucocorticosteroids, β-adrenoblockers, ACE inhibitors, theophylline drugs,expectorants, cough suppressants, anesthetics, anti-allergic drugs (leukotrienereceptor antagonists, H1-histamine receptor blockers, sodium cromoglycatepreparations), antiviral drugs, immunosuppressants, systemic antibacterial drugs for 7days before screening.
21. History of smoking more than 10 pack/years (pack-years: number of cigarettes smokedper day multiplied by the number of years of smoking divided by 20).
22. Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) levels ≥ 2.5 ×highest normal value, serum bilirubin levels ≥ 1.5 × highest normal value.
23. Glomerular filtration rate (GFR) ≤ 60 ml/min.
24. History of cancer of the respiratory system.
25. History of other malignancies, except for patients who have not had the disease in thepast 5 years, patients with fully cured basal cell carcinoma of the skin, or fullycured carcinoma in situ.
26. Serious cardiovascular disease at the time of screening or within 12 months prior toscreening, including: New York Heart Association Class III or IV chronic heartfailure, severe arrhythmias requiring treatment with antiarrhythmic drugs, unstableangina pectoris, myocardial infarction, heart and coronary artery surgery, transientischemic attack or stroke, uncontrolled hypertension with systolic blood pressure > 180 mm Hg Std. and diastolic blood pressure >110 mmHg, pulmonary embolism.
27. Other severe, decompensated or unstable somatic diseases (any disease or conditionthat threatens the patient's life or worsens the patient's prognosis, or makes itimpossible for the patient to participate in a clinical trial).
28. Patient's unwillingness or inability to comply with protocol procedures (in theopinion of the research physician).
29. Pregnancy or breastfeeding (for women).
30. Alcoholism, drug dependence, substance abuse history and/or at the time of screening.
31. A history of schizophrenia, schizoaffective disorder, bipolar disorder or otherpsychiatric pathology.
32. Participation in another clinical trial within 3 months prior to inclusion in thestudy.
33. Other conditions that, in the opinion of the investigating physician, precludeinclusion of the patient in the study. Withdrawal Criteria:
34. Identification of a probable or confirmed case of COVID-19
35. Ineffectiveness of therapy - persistence or increased frequency of cough attacks ≥ 1by visit 3 (day 8-9) compared to visit 1 (day 1).
36. AEs requiring withdrawal of study drug/placebo.
37. The occurrence of any disease or condition during the study that, in the opinion ofthe study physician, worsens the patient's prognosis and also makes it impossible forthe patient to continue participating in the clinical trial.
38. Erroneous inclusion of a patient who does not meet the inclusion criteria and/or meetsthe inclusion criteria.
39. Taking any of the drugs of prohibited therapy, performing a prohibited procedure.
40. The necessity of prescribing prohibited concomitant therapy/procedures.
41. Pregnancy of the patient.
42. Patient's desire to stop participating in the study.
43. Lack of adequate cooperation of the patient with the doctor-researcher during thestudy.
44. Other protocol violations that are significant in the opinion of thephysician-researcher.
45. Other administrative reasons.