A Study of AK104 in Subjects With Locally Advanced Unresectable or Metastatic MSI-H/dMMR Solid Tumors

Inclusion Criteria: * Have signed written informed consent form voluntarily. * Male or female, age ≥ 18 years on the day of signing informed consent form. * ECOG of 0 or 1. * Estimated life expectancy of ≥3 months. * Histologically or cytologically documented locally advanced unresectable or metastatic solid tumors. * Confirmed MSI-H/dMMR status by the central laboratory. * Have experienced documented disease progression during or after at least first-line therapy. * Have radiologically measurable disease based on RECIST 1.1. * Adequate organ function. * Have agreed to take effective contraception from the date of signing the informed consent form until 120 days after the last administration. Exclusion Criteria: * Prior use of investigational products or devices within 4 weeks prior to C1D1 (Cycle 1 Day 1, the first dose of study drug). * Presence of active autoimmune disease that have received systematic treatment in the past 2 years; or that is judged to be possibly relapsed or requires planned treatment by investigators. * Active inflammatory bowel disease or that required treatment (e.g. Crohn's disease, ulcerative colitis or chronic diarrhea). * Prior use of systematic corticosteroid (\> 10 mg daily prednisone equivalents) or other immunosuppressive medications within 14 days prior to C1D1. * Prior exposure to tumor immunotherapy, such as checkpoint inhibitors (eg. anti-PD-1, anti-PD-L1, anti-CTLA-4 antibody), checkpoint agonists or cellular therapy. * Known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation. * Known presence or history of interstitial lung disease. * History of gastrointestinal perforation and/or fistula within 6 months prior to C1D1. * Serious infections within 4 weeks prior to C1D1. * Known presence of active tuberculosis. * Known untreated chronic hepatitis B or chronic hepatitis B virus DNA exceeding 1000 IU/ mL or active hepatitis C virus. * Receipt of recent radiotherapy or anti-tumor treatment within 4 weeks prior to C1D1. * Presence of meningeal metastasis, spinal cord compression, leptomeningeal disease or central nervous system metastasis, with some exceptions. * Uncontrolled pleural effusion, pericardial effusion, or ascites requiring repeated drainage. * Unresolved toxicities from prior anticancer therapy, defined as having not resolved to NCI CTCAE v5.0 Grade 0 or 1, or to levels dictated in the inclusion/exclusion criteria. Hair loss is excluded * Known history of sever hypersensitivity reaction to other monoclonal antibodies. * Known history of allergy or hypersensitivity to AK104 or any of its components. * Any conditions that, in the investigator's opinion, may put subjects treated with the study drug at risks, or interfere with the evaluation of study drug or subject safety, or the interpretation of results.