A Study of IBI129 in Subjects With Unresectable, Locally Advanced or Metastatic Solid Tumors

Inclusion Criteria: 1. Subjects with the ability to understand and give written informed consent for participation in this trial, including all evaluations and procedures as specified by this protocol; 2. At least 1 evaluable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1.; 3. Male or female subjects ≥ 18 years old; 4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1; 5. Anticipated life expectancy of ≥ 12 weeks; 6. Adequate bone marrow and organ function Exclusion Criteria: 1. Participate in any other interventional clinical research except observational (non-interventional) study or in the follow-up phase of the interventional study; 2. Received previous anti-tumor therapy within 4 weeks or 5 half-lives of the anti-tumor regimens before the first administration of study drug, whichever is shorter. 3. Progressed refractory to an antibody drug conjugate that consists of an exatecan derivative that is a topoisomerase I inhibitor. 4. Plan to receive other antitumor therapy during the study excluding palliative radiotherapy for the purpose of symptom (like pain) relief that must also do not have impact on tumor assessment throughout the study; 5. Known symptomatic central nervous system (CNS) metastases.