Comparative study of the pharmacokinetics of XC8, film-coated tablets, 10 mg and XC8, film-coated tablets, 40 mg, when administered once in equal doses (40 mg) on an empty stomach in healthy volunteers.

Inclusion Criteria:

1. Voluntary and handwritten informed consent form signed by a healthy volunteer to participate in the study prior to any of the study procedures;
2. Men and women between the ages of 18 and 45 years (inclusive) of Caucasian race;
3. Verified diagnosis "healthy" (absence of abnormalities according to clinical, laboratory, instrumental methods of examination, stipulated by the protocol);
4. Blood pressure (BP): systolic blood pressure (SBP) of 99 to 129 mmHg (inclusive), diastolic blood pressure (DBP) of 70 to 89 mmHg (inclusive);
5. Heart rate (HR) from 60 to 89 beats/min (inclusive);
6. Respiratory rate (HR) from 12 to 20 per minute (inclusive);
7. Body temperature from 36°C to 36.9°C (inclusive);
8. Body mass index (BMI) of 18.5 kg/m2 ≤ BMI ≤ 30 kg/m2, with a body weight of ≥ 55 kg for men and ≥ 45 kg for women;
9. Consent to use adequate methods of contraception throughout the study and for 30 days after completion; for women of preserved reproductive potential, a negative urine pregnancy test result.

Exclusion Criteria:

1. A history of allergy;
2. Drug intolerance to the active substance XC8 (N-[2-(1H-imidazol-4-yl)-ethyl]-6-oxo-δ-lactam) and/or excipients contained in the studied drug in the anamnesis;
3. Chronic diseases of the kidneys, liver, gastrointestinal tract (GIT), cardiovascular, lymphatic, respiratory, nervous, endocrine, musculoskeletal, genitourinary and immune systems, as well as skin, blood and vision;
4. History of gastrointestinal surgery (except appendectomy at least 1 year prior to screening);
5. Diseases/conditions that, in the opinion of the investigator, may affect absorption, distribution, metabolism or excretion of the investigational drugs;
6. Acute infectious disease less than 4 weeks prior to screening;
7. Taking medications that significantly affect hemodynamics and medications that affect liver function (barbiturates, omeprazole, cimetidine, etc.) less than 2 months prior to screening;
8. Regularly taking an medicine less than 2 weeks before screening and taking a single medicine less than 7 days before screening;
9. Donating blood or plasma less than 3 months before screening;
10. Use of hormonal contraceptives (in women) less than 2 months before screening;
11. The use of depot injections of any drug less than 3 months before screening;
12. Pregnancy or lactation; positive urine pregnancy test for women of preserved reproductive potential;
13. Women of preserved reproductive potential with a history of unprotected intercourse within 30 days prior to study drug administration with an unsterilized partner;
14. Participation in another clinical trial less than 3 months prior to screening or concurrently with the present study;
15. Taking more than 10 units of alcohol (1 unit of alcohol is equivalent to 330 mL of beer, 150 mL of wine or 40 mL of spirits) in the week in the last month before inclusion in the study or anamnestic evidence of alcoholism, drug addiction, drug abuse;
16. Smoking more than 10 cigarettes per day currently, or a history of smoking the specified number of cigarettes during the 6 months prior to screening; disagreement to abstain from smoking for the duration of the hospital stay;
17. Consumption of alcohol, caffeine, and xanthine-containing products 7 days prior to the study drug admission;
18. Consumption of citrus fruits, cranberries and products containing them, preparations or products containing St. John's wort - 7 days before admission to the study drug;
19. Dehydration due to diarrhea, vomiting, or other reason within the last 24 hours prior to study drug administration.
20. Positive blood tests for antibodies to human immunodeficiency virus (HIV) 1 and 2, antibodies to Treponema pallidum antigens, hepatitis B surface antigen (HBsAg), antibodies to hepatitis C virus antigens at screening;
21. Rapid tests of biomaterial (nasopharyngeal and/or oropharyngeal swab) for Severe Acute Respiratory Syndrome Coronavirus 2 antigen (SARS-CoV-2), Coronavirus Disease 2019 (COVID-19) at screening;
22. Clinically significant abnormalities on an electrocardiogram (ECG) history and/or at screening;
23. Positive urinalysis for narcotics and powerful drugs at screening;
24. Positive breath alcohol vapor test at screening.
25. Scheduling an inpatient stay at the time of the study, for any reason other than hospitalization required by this protocol;
26. Inability or inability to meet the requirements of the protocol, perform the procedures prescribed by the protocol, follow the diet, activity regimen.
27. Belonging to a vulnerable group of volunteers: students of higher and secondary medical, pharmaceutical and dental schools, junior staff of clinics and laboratories, employees of pharmaceutical companies, servicemen and prisoners, persons in nursing homes, low-income and unemployed, national minorities, homeless people, vagrants, refugees, persons under guardianship or custody, and persons unable to give consent, and law enforcement officers;
28. Other conditions that, in the opinion of the Researcher, prevent the inclusion of the volunteer in the study or that might lead to early withdrawal of the volunteer from the study, including fasting or a special diet (e.g. vegetarian, vegan, restricted salt intake) or a special lifestyle (night work, extreme physical activity).

Withdrawal Criteria:

1. The volunteer's refusal to further participate in the study;
2. Failure of the volunteer to comply with the rules of participation in the study (skipping study procedures, independent use of drugs prohibited in the study, violation of dietary and lifestyle restrictions, etc.);
3. Occurrence of causes/occurrence during the study of situations that threaten the safety of the volunteer (e.g., hypersensitivity reactions, etc.);
4. Volunteers selected for the study in violation of the inclusion/inclusion criteria;
5. Development of severe adverse event in the volunteer during the study;
6. The volunteer is undergoing or requires treatment that may affect the pharmacokinetic parameters;
7. Missing 2 or more consecutive blood samples or 3 or more blood samples during the same Study Period;
8. Occurrence of vomiting/diarrhea within 4 hours of study drug administration;
9. Positive urine test for narcotics and powerful drugs;
10. Positive breath alcohol vapor test.
11. Positive pregnancy test in women;
12. Positive test for COVID-19;
13. The occurrence in the course of the study of other reasons that prevent the study according to the protocol.