The main purpose of this study is to evaluate the safety and tolerability of IBI3020 and to determine the maximum tolerated dose (MTD) and/or the recommended dose for expansion (RP2D) of IBI3020.

Inclusion Criteria:

Participants must satisfy all of the following criteria to be enrolled into the study:

1. Participants have 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. Male or female participants ≥ 18 years old. For Part 1, age ≥ 18 years and ≤ 75 years;
3. Histologically or cytologically confirmed unresectable, locally advanced or metastatic solid tumors which have received available standard therapies and have disease progression, or unacceptable toxic effects, or contraindications;
4. At least 1 measurable lesion as defined per RECIST v1.1 within 28 days prior to the first dose of IBI3020;
5. Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0-1;
6. Minimum life expectancy of 12 weeks;
7. Adequate bone marrow and organ function confirmed at screening period;
8. Participants, both male and female, who are not of childbearing potential or who agree to use at least 1 highly effective method of contraception during the study.

Exclusion Criteria:

Participants who meet any of the following criteria will be disqualified from entering the study:

1. Previous treatment with CEACAM5-targeted therapy;
2. Prior anti-cancer therapy within the wash-out period;
3. Received live vaccines within 4 weeks or cancer vaccine within 3 months;
4. Potent cytochrome P450 3A4 (CYP3A4) inhibitors within 2 weeks or 5 half-lives;
5. Has adverse reactions resulting from previous anti-tumor therapies, which have not resolved to Grade 0 or 1 toxicity according to NCI CTCAE v5.0;
6. Known allergies, hypersensitivity, or intolerance to IBI3020 or its excipients;
7. Undergone major surgery within 4 weeks, or who have severe unhealed wounds;
8. Known symptomatic central nervous system (CNS) metastases;
9. Uncontrolled diseases or conditions;
10. History of pneumonitis requiring corticosteroids therapy, or history of clinically significant lung diseases;
11. History of thromboembolic event within 6 months;
12. Under neurological, psychiatric or social condition;
13. Women who are pregnant, have positive results in pregnancy test or are lactating;
14. Not eligible to participate in this study at the discretion of the investigator;
15. Participating in any other interventional clinical research.