This first-in-human open-label, multicenter, dose-escalation and expansion study is designed to evaluate the safety, tolerability, and primary efficacy of IBI321 in participants with locally advanced, recurrent, or metastatic incurable tumors for whom standard therapy does not exist, has proven to be ineffective or intolerable.

Inclusion Criteria:

1. Subjects able to give voluntary informed consent, understand the study and are willing to follow and complete all the test procedures.
2. Patients with advanced solid tumors who had failed standard treatment.
3. Male or female subjects ≥18 years and ≤75 years.
4. At least one measurable lesion per RECIST version 1.1
5. Eastern Cooperative Oncology Group (ECOG) Performance Status ≤1
6. Life expectancy of ≥ 12 weeks.
7. Adequate hematologic and end organ function

Exclusion Criteria:

1. Any anti-cancer therapy, whether investigational or approved, including chemotherapy, hormonal therapy, targeted therapy, or immunotherapy.
2. Failure to recover from adverse events from the most recent anti-tumor
3. Acute or chronic hepatitis B, hepatitis C or human immunodeficiency virus (HIV) infection.
4. Subjects with CNS metastasis unless they are asymptomatic or adequately treated with radiotherapy and/or surgery and subjects are neurologically stable with minimal residual symptoms/signs.
5. Any other serious underlying medical (e.g., uncontrolled hypertension, active uncontrolled infection, active gastric ulcer, uncontrolled seizures, cerebrovascular incidents, gastrointestinal bleeding, severe signs and symptoms of coagulation and clotting disorders, other serious cardiac conditions not listed in exclusion criteria), psychiatric, psychological, familial or geographical condition that, in the judgment of the investigator, may interfere with the planned staging, treatment and follow-up, affect patient compliance or place the patient at high risk from treatment-related complications.
6. Pregnancy, lactation, breastfeeding.