This is a Phase Ib clinical study to evaluate the safety, tolerance, pharmacokinetics and efficacy of AK101 in subjects with moderately to severely active ulcerative colitis.

This is a phase Ib, randomized, double-blind, placebo-controlled, dose-escalation, two-phase study evaluating the safety, tolerability, pharmacokinetics, and pharmacodynamics of AK101 in subjects with moderately to severely active ulcerative colitis. The study consists of two parts. Part 1 is single-ascending-dose induction phase study, and Part 2 is a multiple subcutaneous maintenance therapy study followed by a single-dose induction treatment.

Key Inclusion Criteria:

• Body mass index (BMI) ≥ 18 and ≤ 28 kg /m2 for male or female patients aged between 18 and 65 years (including upper and lower limits).
• Confirmed diagnosis of ulcerative colitis (UC) for at least 3 months before screening, and the diagnosis of UC must be confirmed by endoscopic and histological evidence.
• Has moderately to severely active UC,defined as the adapted Mayo score (excluding PGA) of 5-9 (including upper and lower limits), Mayo endoscopic subscore ≥ 2 within 10 days before the first administrationof study drug and rectal bleeding subscore ≥ 1.
• Have evidence of ulcerative colitis extending proximal to the rectum (≥15 cm of involved colon).
• Demonstrated intolerance or inadequate response to conventional therapy and tofacitinib (not a biologic) and biologic therapies.
• For women with fertility, the serum pregnancy test must be negative during the screening period; Or women without fertility.If male and female subjects with sexual life and fertility voluntarily take contraceptive measures during the treatment and at least 6 months after the last Administration.

Key Exclusion Criteria:

• Suspected or confirmed Crohn's disease (CD), undiagnosed type of colitis.
• Suffering from severe generalized colitis.
• Previous colectomy (total or subtotal resection) with ileal pouch, Kock pouch or ileostomy for ulcerative colitis.
• Patients who have received IL-12 / 23 or IL-23 target drug treatment.
• Received Natalizumab or other drugs that regulate B cells or T cells within 12 months before randomization, such as Rituximab, Alemtuzumab, Abatacept treatment.
• Received infliximab and adalimumab 2 months before randomization, and received Vedolizumab and other biological treatments 3 months before randomization.
• Patients with active hepatitis B virus (HBV) infection or active hepatitis C virus (HCV).
• Suffering from human immunodeficiency virus (HIV) or syphilis.
• Active tuberculosis or Latent tuberculosis infection.
• Has a history of, or ongoing, chronic or recurrent infectious disease.,
• Suffering from any mental illness, or suffer from a serious or active disease, the investigators think may interfere with the subject's treatment, evaluation or compliance with the study protocol.
• Patients with malignant tumors (except skin basal cell carcinoma and cervical carcinoma in situ that have been cured and have no signs of recurrence) or lymphoproliferative diseases, and cervical diseases caused by HPV.