The study focusses on the evaluation of safety and tolerability of the XC8. The design of the study involves sequential dosing of cohorts (group of volunteers), taking increasing doses of the product after receiving conclusion and recommendation for further continuation of the study from the Dose Escalation Committee.

Inclusion Criteria:

1. Men and women aged 18 to 50 years;
2. Generally good health;
3. Body mass index of 19 to 30 kg/m² and >50 kg body weight;
4. Female subjects who are post-menopausal (no menstrual period for a minimum of 1 year), or surgically sterile (bilateral tubal ligation, bilateral oophorectomy, or hysterectomy), or practice a highly effective method of birth control, i.e. resulting in a failure rate of less than 1% per year when used consistently and correctly (e.g. implants, injectables, combined oral contraceptives, some intra-uterine devices, sexual abstinence, or vasectomized partner). The birth control method must have been applied for at least 1 cycle before and until 3 months after administration of the study medication.
5. Male subjects with a female partner of child-bearing potential agree to use a medically acceptable method of contraception (e.g. condoms, sexual abstinence, vasectomy) during the study, and until 3 months after the last intake of study medication.
6. Subjects are willing and able (in the opinion of the investigator) to understand and comply with the procedures and evaluations of the study.
7. Subjects must be willing and legally able to give written informed consent.

Exclusion Criteria:

1. Hepatic or renal disease; any other disease, which may influence the clinical trial results or may lead to health worsening during the trial (according to the investigator's opinion);
2. Clinically significant laboratory abnormalities;
3. Use of any medication, including prophylaxis, within 1 month before screening (including herbal preparations and nutritional supplements);
4. Positive test for human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis B virus HBV at Screening;
5. Irregular sleep (e.g. night work, sleep disturbances, insomnia, returning from another time zone, etc.);
6. History or current evidence of alcohol or drug abuse; alcohol or drug intake within 4 days before Screening;
7. History or current evidence of allergic reactions (including reactions to medications and food);
8. History or current evidence of symptomatic rhinitis within 2 years before Screening (allergic rhinitis, non-allergic rhinitis, or hay fever, excluding short-term viral infection - cold or influenza);
9. Blood or plasma donation, or surgery (in hospital) within 12 weeks of Screening;
10. Lactating or pregnant females; a positive pregnancy test before the first administration of investigational medicinal product or breastfeeding;
11. Current or previous (within 3 months of enrollment) treatment with another investigational drug and/or medical device or participation in another clinical study;
12. Previous enrollment in this clinical study;
13. Inability to understand or follow protocol instructions;
14. Smoking within 3 months before screening or throughout the study;
15. Lactose intolerance;
16. History of allergic reactions to XC-8 or any inactive ingredients of the trial medication;
17. Employees of the sponsor or subjects who are employees or relatives of the investigator;