⁃ 1\. Diagnosis of ulcerative colitis with involvement of the colon proximal to the rectum (≥15 cm from the distal edge of the anal canal), established ≥3 months before signing the ICF and confirmed by endoscopic examination data.

⁃ 2\. Moderate to severe active ulcerative colitis with a modified Mayo score (mMS) of ≥4 and ≤9 points, which includes an endoscopic component of ≥2 points (according to a central independent review) and a stool blood score of ≥1 point.

⁃ 3\. Inadequate response to therapy according to the investigator's assessment, manifested by at least one of the following signs:

• Persistent symptoms of disease activity despite treatment with at least one course of glucocorticoids including prednisolone at a dose of ≥40 mg/day or equivalent or budesonide ≥9 mg/day or equivalent for at least 2 weeks with oral administration (at least 1 week with intravenous administration at a dose equivalent to oral prednisolone ≥40 mg/day).

• Steroid dependence manifested by an increase in disease activity after initial improvement, with a decrease in the dose of glucocorticoids below the dose equivalent to 10 mg of oral prednisolone per day, within 3 months from the beginning of treatment, or a relapse of the disease within 3 months after the end of glucocorticoid use.

• Persistent symptoms of disease activity despite treatment with at least one course of immunosuppressants (azathioprine at a dose of ≥2.0 mg/kg and/or 6-mercaptopurine at a dose of ≥1.0 mg/kg) for ≥12 weeks, or in response to another treatment regimen with these drugs according to a regional standard of care.

• Primary lack of response to therapy with TNFa inhibitors and/or anti-integrins, and/or IL-12/23 inhibitors, and/or Janus kinase inhibitors, and/or sphingosine-1-phosphate receptor modulators, defined as the persistence of symptoms of disease activity despite at least one course of induction of remission according to a treatment scheme approved by the regional standard.

• Loss of response to therapy with TNFa inhibitors and/or anti-integrins, and/or IL-12/23 inhibitors, and/or Janus kinase inhibitors, and/or sphingosine-1-phosphate receptor modulators, defined as the appearance of symptoms of disease activity after initial improvement as a result of treatment with at least one course of induction of remission and at least one course of maintenance of remission according to a treatment scheme approved by the regional standard.

• A history of intolerance to glucocorticoids and/or immunosuppressants (azathioprine, 6-mercaptopurine) and/or biological therapy/targeted immunosuppressants (TNFa inhibitors, anti-integrins, anti-IL-12/23 monoclonal antibodies, Janus kinase inhibitors, sphingosine-1-phosphate receptor modulators) established by the treating physician.

⁃ 4\. Maintaining a stable dose of concomitant medications for ≥2 weeks prior to signing the ICF and in the screening period for glucocorticoids and 5-ASCs and for ≥4 weeks prior to signing the ICF and in the screening period for immunosuppressants (azathioprine, 6-mercaptopurine).