This study is a multicenter, open-label, phase II study of YL202 in China to evaluate the efficacy, safety, and PK characteristics of YL202 in the following selected patients with advanced solid tumors.

This study is a multicenter, open-label, phase II study of YL202 in China to evaluate the efficacy, safety, and PK characteristics of YL202 in the advanced NSCLC/BC/HNSCC/colorectal cancer/HER2-positive gastric cancer/cervical cancer/ovarian cancer and etc.

Inclusion Criteria:

1. Subjects who are aware of relevant trial information before the start of the trial, and voluntarily sign and date on the informed consent form (ICF).
2. Subjects aged from 18-75 (inclusive) years.
3. Histologically or cytologically confirmed at diagnosis of NSCLC/BC/HNSCC/other locally advanced or metastatic solid tumors including but not limited to colorectal cancer, HER2-positive gastric cancer, cervical cancer, ovarian cancer, etc..
4. At least one extracranial measurable lesion according to RECIST 1.1.
5. Archived or fresh tumor tissue samples can be provided.
6. With Eastern Cooperative Oncology Group performance status (ECOG PS) score of 0 or 1.
7. The function of organs and bone marrow meets the requirements within 7 days before the first dose.
8. Female subjects of childbearing potential must agree to adopt highly effective contraceptive measures from screening throughout the study period and within at least 6 months after the last dose of the investigational product. Male subjects must agree to adopt highly effective contraceptive measures from screening throughout the study period and within at least 6 months after the last dose of the investigational product.
9. With expected survival ≥ 3 months.
10. Be capable of and willing to comply with the visits and procedures stipulated in the study protocol.

Exclusion Criteria:

1. With prior drug therapy targeting HER3 (including antibodies, antibody-drug conjugates [ADCs]), chimeric antigen receptor T-cell immunotherapy (CAR-T), and other drugs).
2. Previously intolerant to topoisomerase I inhibitors or ADC therapy composed of topoisomerase I inhibitors.
3. Are participating in another clinical study, unless it is an observational (non-interventional) clinical study or in the follow-up period of an interventional study.
4. The washout period from the previous anti-tumor therapy is insufficient before the first dose of the investigational product.
5. Patients who have received major surgery (excluding diagnostic surgery) within 4 weeks before the first dose of the investigational product or those who are expected to receive major surgery during the study.
6. Prior treatment with allogeneic bone marrow transplantation or solid organ transplantation.
7. Prior treatment with systemic steroids (prednisone > 10 mg/day or equivalent) or other immunosuppressive treatment within 2 weeks before the first dose of the investigational product.
8. Patients who have received any live vaccine within 4 weeks before the first dose of the investigational product or those who plan to receive live vaccine during the study period.
9. With meningeal metastasis or cancerous meningitis.
10. With brain metastasis or spinal cord compression.
11. Patients with uncontrolled or clinically significant cardiovascular diseases.
12. Clinically significant complicated pulmonary disorders.
13. Patients diagnosed with Gilbert syndrome.
14. Those with uncontrolled effusion in the third space requiring repeated drainage.
15. With a medical history of gastrointestinal perforation and/or fistula within 6 months before the first dose, or with active gastric and duodenal ulcers, ulcerative colitis, or other gastrointestinal diseases that may lead to hemorrhage or perforation according to the investigator.
16. With serious infection before the first dose.
17. With known human immunodeficiency virus (HIV) infection.
18. With active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection.
19. With a medical history of any other primary malignancies within 5 years before the first dose of the investigational product.
20. Unrelieved toxicity of previous anti-tumor therapy.
21. With a history of severe hypersensitivity to inactive ingredients in the raw materials and drug product or other monoclonal antibodies.
22. Lactating women, or women who are confirmed pregnant via a pregnancy test within 3 days before the first dose.
23. With any diseases, medical conditions, organ system dysfunction, or social conditions that may interfere with the ability of subjects to sign the ICF, adversely affect the ability of subjects to cooperate and participate in the study, or affect the interpretation of study results, including but not limited to mental illness or substance/alcohol abuse, in the opinion of the investigator.