A Study to Assess the Efficacy and Safety of XC221 in Patients With COVID-19

Inclusion Criteria:

1. Signed Informed Consent Form.

2. Patients of both sexes aged 18 to 75 years inclusive.

3. Diagnosed COVID-19 based on:

- positive laboratory tests confirming the SARS-CoV-2 presence, performed no
earlier than 14 days before hospitalization. It is allowed to determine the
SARS-CoV-2 by the PCR or by another method according to the MoH Temporary
Guidelines; and / or

- bilateral alterations in lungs, typical for COVID-19, according to CT scan of the
chest.

4. Patients with moderate or severe form of disease (t > 38.0°C; respiratory rate (RR)
>22 / min; Sp02 <95%) not requiring non-invasive / invasive ventilation and / or
high-flow oxygenation (HFNT), and / or extracorporeal membrane oxygenation (EMO) at
the time of screening and randomization (based on the MoH Temporary Guidelines).

5. Patients requiring oxygen therapy (oxygenation through a nasal cannula, a simple
facemask or other similar oxygen delivery device) with a category "4" according to the
WHO scale.

6. Time from hospitalization to the first drug administration should not exceed 48 hours.
This item is to be assessed only when re-evaluating the inclusion / exclusion criteria
at the Randomization visit and treatment initiation.

7. Disease duration is no more than 7 full days since the moment of appearing one or more
of the symptoms below until the first dose of the drug administration:

- temperature increase;

- dry cough or cough with little phlegm;

- shortness of breath;

- myalgia;

- fatigue;

- feeling of congestion in the chest;

- reduced sense of smell and / or taste.

8. For women only: negative pregnancy test result. Pregnancy testing is not required for
women of not childbearing potential (WONCBP): women who are in menopause (defined as
an absence of menstruation for at least 2 years or more), or women who undergone
surgical sterilization (hysterectomy, bilateral oophorectomy, tubal ligation), or
women with a clinical diagnosis of "infertility". The presence of surgical
sterilization and infertility should be confirmed by patient's claim or by relevant
document confirming this condition.

9. Consent to use reliable method of contraception throughout the study period.

10. Patients who are able to understand and comply with treatment and procedures during
the study.

Exclusion Criteria:

1. Known or suspected hypersensitivity to the active substance or to excipients of the
drug XC221 or placebo

2. Known or suspected hypersensitivity to standard therapy drugs specified in The MoH
Temporary Guidelines.

3. Lactase deficiency, lactose intolerance, glucose-galactose malabsorption.

4. Presence or suspicion of oncological diseases by the day of criteria assessment or in
medical history (within the last 2 years).

5. Presence of autoimmune diseases by the day of criteria assessment or in medical
history.

6. Neutropenia (0.5 * 10^9 /l).

7. Exceeding the upper limit of normal for ALT and AST by 5 times or more.

8. Thrombocytopenia 50000 / mm^3.

9. Pregnancy.

10. Lactation.

11. Presence of serious lung diseases, including, but not limited to the following
diseases: moderate and severe bronchial asthma, severe and extremely severe COPD,
interstitial lung disease, pulmonary hypertension, pulmonary fibrosis, surgical
interventions on the lungs, tuberculosis (including suspicion of tuberculosis based on
the results of CT examination at screening).

12. Patients with type 1 diabetes mellitus and / or decompensated type 2 diabetes
mellitus.

13. Heart failure, NYHA functional class III - IV.

14. Chronic liver failure stage II (decompensated) and higher.

15. The need of renal replacement therapy at the time of inclusion of the patient.

16. Organ transplantation in medical history.

17. Medical history of epilepsy or the need for anticonvulsant therapy.

18. Major depressive disorder, anxiety, other mental disorders requiring medical
correction.

19. Acute cerebrovascular accident, stroke or transient ischemic attack within 90 days
before screening.

20. Administration of any antiviral and / or immunomodulatory drugs after the
manifestation of COVID-19, with the exception of those specified in the MoH Temporary
Guidelines.

21. Any immunosuppressive therapy (including tocilizumab / sarilumab) within 90 days prior
to randomization, or the need of immunosuppressive therapy at the time of
randomization.

22. Administration of systemic glucocorticosteroids within 90 days prior to randomization,
or the need of systemic glucocorticosteroids at the time of randomization.

23. Administration of vaccines against viral infections within 90 days prior to
randomization.

24. Patients receiving other experimental drugs, drugs not approved in the Russian
Federation, or participating in other clinical trials within 30 days before screening.

25. Patients abusing alcohol or psychotropic drugs and other drugs by the day of criteria
assessment or during the last year.

26. Patients with other serious, unstable, or clinically significant medical or
psychological conditions that, in the opinion of the investigator, may preclude the
patient's participation in the study.

27. Expected death within 48 hours after randomization.

28. Expected hospital discharge within 48 hours of randomization.