Patient description: A 39-year-old man came to the clinic with cough and shortness of breath that was not relieved by his inhaler. He had these symptoms for 5 days during the past 2 weeks. He doubled his oral corticosteroids in the past week. He is a chef with a history of asthma for 3 years, suffering from frequent cough, wheezing, and shortness of breath and chest tightness. The symptoms become more bothersome within 1-2 hours of starting work every day and worsen throughout the work week. His symptoms improve within 1-2 hours outside the workplace. Spirometry was performed revealing a forced expiratory volume in the first second (FEV1) of 63% of the predicted. His past medical history is significant for seasonal allergic rhinitis in the summer. He doesn't smoke or use illicit drugs. His family history is significant for asthma in his father and sister. He currently uses inhaled corticosteroid (ICS) and fluticasone 500 mcg/salmeterol 50 mcg, one puff twice daily.

Clinical trial eligibility criteria: eligible ages (years): 18.0-65.0,  Bronchial Asthma Eosinophilic Asthma Signed Informed Consent Form; 2. Male and female non-smokers of 18 to 65 years of age (inclusive); 3. The diagnosis of asthma not earlier than 12 months prior to screening; 4. Steps 2 and 3 according to Global Initiative for Asthma (GINA, 2019) recommendations; 5. Patients receiving stable ICS doses with or without long-acting β2-agonists; 6. Еosinophil blood level measured twice at a 1 week interval, of ≥ 300 cells/µl ; 7. Signs of partially controlled BA within 4 weeks prior to screening according to GINA 2019 recommendations; 8. FEV1 value prior to the use of bronchodilators in the range of 55 to 85% of the proper value (inclusive); 9. Consent of patients to use adequate contraception methods throughout the study; 10. Ability to comply with all the study protocol requirements  Pregnant or lactating women, or women planning to get pregnant during the clinical study; women of child-bearing potential (including those without history of surgical sterilization and women with <2 years post-menopause) not using adequate contraception methods; 2. Smoking for 1 year prior to screening or previous smoking history of more than 10 packs/year; 3. Severe exacerbations or uncontrolled BA within 3 months prior to screening; 4. Chronic obstructive pulmonary disease (COPD) or other serious lung diseases other than asthma; 5. Inflammatory diseases of the oral cavity at screening; 6. An acute infectious disease within 30 days prior to screening; 7. Participation in any clinical study or any study drug administration within 30 days prior to screening; 8. Taking or indications for taking of prohibited drugs (including anti-leukotriene preparations, modified-release theophylline, etc.); 9. Indications for long-term use of systemic steroids or nonsteroidal anti-inflammatory drugs or drugs affecting on the immune system; 10. The need for periodical intake of antihistamines during the study (stable doses of antihistamines for at least 1 month prior to screening and throughout the study is allowed); 11. Immunosuppressant therapy within 3 months prior to screening; 12. Anaphylaxis, generalized urticaria, or angioedema within 1 year prior to screening; 13. Known allergies, hypersensitivity or contraindications for XC8 or its ingredients; 14. A history of systemic autoimmune diseases or vascular collagenosis; 15. Malignancies within the last 5 years (except for the cured basal cell carcinoma); 16. Significant cardiovascular diseases diagnosed at present or within 12 months prior to screening; uncontrolled hypertension with systolic blood pressure > 180 mm Hg and diastolic blood pressure > 110 mm Hg; pulmonary embolism or deep vein thrombosis; 17. Nephrotic syndrome, moderate to severe chronic renal failure or significant renal impairment with creatinine level >1.5 mg/dL (132 μM/l) in males and > 1.4 mg/dL (123 μM/l) in females or glomerular filtration rate < 60 mL/min; 18. HIV, hepatitis B or C, history of cirrhosis; 3-fold increased serum aspartate aminotransferase or alanine aminotransferase > above the Upper Limit of Normal; 2-fold increased total bilirubin level > above at screening; 19. Anemia (hemoglobin level ≤ 10.5 g/dL in females or ≤ 11.5 g/dL in males); significant blood loss or collection of at least one volumetric unit of donated blood (> 500 mL), or blood transfusion within 12 weeks prior to screening; 20. Any concomitant disease, other than asthma, not controlled by a stable therapy regimen; 21. Drugs or alcohol abuse at screening or in the past, which, in the Investigator's opinion, makes the patient not eligible for participation in the study; 22. Inability to read or write; unwillingness to understand and comply with the protocol procedures; non-compliance with the drug dosing regimen or procedures which, in the Investigator's opinion, may affect study results or the patient's safety and prevent the patient's participation in the study; any other concomitant diseases or severe mental disorders, which make the patient ineligible for participation in the study, limit the legal basis for Informed Consent procedure, or may affect the patient's ability to participate in the study