This is an open-label, multicenter, phase II study. The purpose of this study is to evaluate the safety, tolerability and preliminary anti-tumor activity of SKB518 in patients with lung cancer. Eligible subjects will receive SKB518 monotherapy, until radiographic disease progression, intolerable toxicity, discontinuation of study treatment required by the subject, or other protocol-specified treatment discontinuation criteria, whichever occurs first.

Inclusion Criteria:

1. Age between 18 and 75 years old at the time of signing the informed consent form, applicable to both males and females.
2. Non-small cell lung cancer (NSCLC) or small cell lung cancer(SCLC) confirmed by histology or cytology.
3. At least one measurable tumor lesion per RECIST v1.1.
4. Performance status score of 0-1 according to the Eastern Cooperative Oncology Group (ECOG) scale.
5. Expected survival period ≥ 12 weeks.
6. The function of important organs meets the requirements of the protocol.

Exclusion Criteria:

1. Symptomatic or uncontrolled cardiovascular disease
2. History of noninfectious pneumonitis/interstitial lung disease (ILD) that required steroids or has current pneumonitis/ILD;
3. Subjects with the disease that requires systemic corticosteroid therapy (prednisolone or equivalent dose of similar drugs at a dose of >10 mg/d) or other immunosuppressive therapy within 14 days before the first dose.
4. Human immunodeficiency virus (HIV) positive or history of acquired immunodeficiency syndrome (AIDS); known active syphilis infection.
5. The Investigator considers other situations that will interfere with the evaluation of the study intervention or the safety of the subjects or the interpretation of the results of the study.