Open Label Study to Evaluate the Safety and Efficacy of AK101 Injection Subcutaneously in Subjects With Psoriasis

Key Inclusion Criteria: * Applicable for subjects who have completed the previous Akeso trial (AK101-302) with AK101 injection: 1. Subjects can continue to participate in this study based on assessment of investigator. 2. Subjects voluntarily participate in this study. 3. Subjects who are women of childbearing potential must be practicing an adequate, medically acceptable method of birth control during the treatment period and for at least 6 months after the last study drug administration. * Applicable for subjects newly enrolled: 1. Male or female subjects aged ≥ 18 years old. 2. Subjects diagnosed with moderate-to-severe plaque psoriasis and are applicable to systematic treatment. 3. At screening and baseline, PASI score ≥ 12, Body Surface Area BSA (BSA) ≥ 10%, sPGA ≥ 3. 4. Subjects who are applicable for biological agents, based on the assessment of investigator. 5. Subjects who are women of childbearing potential must have a negative pregnancy test at screening and must be practicing an adequate, medically acceptable method of birth control for at least 6 months after the last study drug administration. Key Exclusion Criteria: * Applicable for subjects who have completed the previous Akeso trial (AK101-302) with AK101 injection: 1. Subjects who have severe AE or SAE occurred in an Akeso trial with AK101 injection. 2. Subjects who used prohibited drugs in an Akeso trial with AK101 injection. 3. Subjects performed poor compliance in an Akeso trial with AK101 injection, based on the assessment of investigator. 4. Subjects with any other disease, abnormal physical examination or abnormal laboratory examination leading to inapplicable for participating this study, based on the assessment of investigator. * Applicable for subjects newly enrolled: 1. Forms of psoriasis other than chronic plaque-type psoriasis. 2. History or evidence of active TB. Patients with evidence of latent tuberculosis may enter the trial after sufficient treatment had initiated and maintained according to protocol. 3. Positive results of confirmatory test for hepatitis B, hepatitis C, human immunodeficiency virus (HIV) or syphilis. 4. History of repeated chronic infection, had any serious infection or systemic infection within 2 months before screening. 5. History of prohibited psoriasis treatments within 2/4 weeks before randomization. 6. History of IL-12/23 or IL-23 inhibitors therapy. 7. Inadequate washout period of prior biological therapy. 8. History of malignant tumour within 5 years before screening. 9. Any medical or psychiatric condition, laboratory, or ECG parameter which, in the opinion of the Investigator would place the subject at risk, interfere with participation or interpretation of the study.