A double-blind, randomized, placebo-controlled, Phase I clinical study of the safety and tolerability of increasing doses of drug XC221 after single and repeated oral administration in healthy volunteers. The volunteers received the study drug once, and then continued daily intake for 5 days after a 6-day break. The primary objective of the study was to evaluate the safety and tolerability profile for drug XC221 after single and multiple administration based on the frequency and severity of adverse events and changes in vital signs, laboratory results, electrocardiography and results of the physical examination. The secondary objective of the study was to assess pharmacokinetics of active pharmaceutical substance XC221GI and its metabolite XC221A.

One Russian center was approved for participation in this study. One center was initiated. Healthy volunteers were enrolled in 1 center. The study consisted of 4 periods: screening, single administration, multiple administration and follow-up.

All eligible subjects were randomized into the study in appropriate cohort groups sequentially. Cohort 1 - XC221 or Placebo 60 mg once and then daily 5 days after a 6-day break; Cohort 2 - XC221 or Placebo 200 mg once and then daily during 5 days after a 6-day break. The decision regarding increasing of the study drug dose for a subsequent cohort was made by the Data Safety Monitoring Committee on the basis of preliminary safety results assessment. A total of 24 volunteers received XC221 (60 mg or 200 mg) and a total of 8 volunteers received the placebo during the study participation. The follow-up period lasted for 4 weeks.

Inclusion Criteria:

1. Non-smoking men aged 18 to 45 years (inclusive);
2. Verified diagnosis "healthy" according to standard clinical, laboratory and instrumental methods of examination;
3. Body mass >50 kg and body mass index of 18.5 to 30 kg/m2 (inclusive);
4. Negative result of tests for alcohol and drugs;
5. Consent to use reliable methods of contraception during the study and 3 months after its completion (condoms with spermicide);
6. Signed patient information sheet and informed consent form for participation in the study.

Exclusion Criteria:

1. Chronic diseases of cardiovascular, bronchopulmonary, neuroendocrine, musculoskeletal system and also disease of digestive tract, liver, kidneys, blood;
2. Laboratory abnormalities at screening;
3. Surgical interventions on digestive tract in the anamnesis (except for an appendectomies);
4. Systolic pressure is less than 90 mm Hg. or more than 130 mm Hg., diastolic pressure is less than 60 mm Hg. or more than 85 mm Hg., pulse rate less than 60/min. or more than 80/min.;
5. Course intake of medicinal products (including herbs and biologically active additives) for preventive or curative purposes within 1 month prior to screening;
6. Antibodies to HIV and hepatitis C virus, the presence of the hepatitis B surface antigen, a positive syphilis test;
7. The presence of a sleep disorder (for example, night work, sleep disturbances, insomnia, recent return from another time zone, etc.);
8. Signs of alcohol or drug abuse; taking alcohol or drugs during 4 days before screening; smoking 3 months before screening;
9. History of allergies (including medicines and food products);
10. Blood donation / plasma, surgical intervention (in a hospital environment) during 12 weeks before screening;
11. Participation in other clinical trials or taking the study drug during 3 months before screening;
12. Acute infectious diseases less than 4 weeks before the start of the study;
13. Impossibility to understand or follow protocol instructions/

Blinding was carried out by using Placebo equivalent to XC221 tablets without active substance and the corresponding labeling of the study drug.