This is a Phase I clinical study of HS-20108. The purpose of this study is to evaluate the safety, tolerability, PK and efficacy of intravenous HS-20108 in patients with advanced solid tumors.

This is a multicenter, open-label Phase I clinical study to evaluate the safety, tolerability, PK and efficacy of intravenous HS-20108 in patients with advanced solid tumors. The study consists of Phase Ia (dose escalation) and Phase Ib (dose expansion). In Phase Ia, dose escalation in monotherapy and combination therapy will conduct to identify the maximum tolerated dose (MTD) in patients with advanced solid tumors. In Phase Ib, potential indications (such as small cell lung cancer or neuroendocrine carcinoma) will be selected for the early proof-of-concept study of HS-20108 at different doses in monotherapy and combination therapy based on the study data from Phase Ia, the translational medicine research data and R&D progress in the field.

Inclusion Criteria:

1. Men or women aged more than or equal to (≥) 18 years.
2. Participants with pathologically confirmed advanced solid tumors.
3. At least one measurable lesion in accordance with RECIST 1.1
4. Fresh or archival tumor tissue available for submission.
5. Eastern Cooperative Oncology Group (ECOG) performance status: 0~1.
6. Estimated life expectancy >12 weeks.
7. Reproductive-age women agree to use adequate contraception and cannot breastfeed while participating in this study and for a period of 6 months after the last dose. Likewise, men also consent to use adequate contraceptive method within the same time limit.
8. Females must have evidence of non-childbearing potential.
9. Signed and dated Informed Consent Form.

Exclusion Criteria:

1. Treatment with any of the following:

   Having received cytotoxic chemotherapy agents, investigational drugs, Chinese medicine treatment with anti-tumor indications, or other anti-tumor therapy (including endocrine therapy, molecular targeted therapy, or biotherapy) within 14 days before the first dose of study treatment.

   Having received macromolecular anti-tumor drug therapy (including immunotherapy, such as monoclonal antibody drugs and bispecific antibody drugs) within 28 days before the first dose of study treatment.

   Local radiotherapy for palliation within 2 weeks of the first dose of study drug, or patients received more than 30% of the bone marrow irradiation, or large-scale radiotherapy within 4 weeks of the first dose.

   Major surgery (including craniotomy, thoracotomy, or laparotomy, etc.) within 4 weeks of the first dose of study drug.

2. Inadequate bone marrow reserve or serious organ dysfunction.

3. Uncontrolled pleural effusion or ascites or pericardial effusion.

4. Known and untreated, or active central nervous system metastases.

5. Active autoimmune diseases or active infectious disease

6. Known to have interstitial pneumonia or immune pneumonia

7. History of severe allergic reaction, serious transfusion reactions or Allergy to any component of HS-20108

8. The subject who is unlikely to comply with study procedures, restrictions, or requirements judged by the investigator.

9. The subject whose safety cannot be ensured or study assessments would be interfered judged by the investigator.

10. Pregnant women, breastfeeding women or woman who has a child-bearing plan during the study.

11. History of neuropathy or mental disorders, including epilepsy and dementia.