Small cell lung cancer (SCLC), who failed or intolerant to available standard treatments;

Tissue sample positive for DLL3 expression;

Life expectancy ≥ 3 months;

Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1;

Female and Male patients must agree to use a reliable form of contraception during the study treatment period and for at least 6 months after the last dose of the study drug.

Patients having received any of the following treatments:

Chemotherapy, biotherapy, endocrine therapy (except for hormone replacement), and biological targeted medicines ≤ 4 weeks before the study entry. Local palliative radiotherapy and a small molecule targeted therapy ≤ 2 weeks (or 5 half-lives, whichever is longer) before the study entry;

Systemic immunosuppressive medications, such as corticosteroid (doses > 10 mg/day prednisone or equivalent dose) within 14 days prior to the study entry;

Use of any vaccines against viral infections (COVID-19, influenza, varicella, etc.) within 4 weeks of study entry;

Patients received any blood transfusion, EPO, G-CSF, albumin infusion and renal replacement therapy within 14 days prior to study entry;

A history of severe, life-threatening immune-mediated adverse events or infusion-related reactions during previous anti-tumor immunotherapy, including events that led to permanent discontinuation of treatment;

Active infection (such as acute bacterial infection, tuberculosis, active hepatitis B/C, active syphilis, or active human immunodeficiency virus infection);

Known allergy to other mAbs or any antibody excipients; the history of a severe allergic reaction, anaphylactoid or other hypersensitivity reactions to humanized antibodies or fusion proteins;

A female who is pregnant or nursing;

Patients were deemed unsuitable for participating in the study by the investigator for any reason.