• Voluntarily sign the informed consent and follow the requirements of the protocol;

• Age ≥18 years old;

• Expected survival time ≥3 months;

• Patients with recurrent small-cell lung cancer after failure of anti-PD-1/PD-L1 monoclonal antibodies and platinum-based chemotherapy;

• Consent to provide archival tumor tissue samples or fresh tissue samples of primary or metastatic lesions within 3 years;

• Must have at least one measurable lesion according to RECIST v1.1 definition;

• ECOG 0 or 1;

• Toxicity of previous antineoplastic therapy has returned to ≤ grade 1 defined by NCI-CTCAE v5.0;

• No severe cardiac dysfunction, left ventricular ejection fraction ≥50%;

⁃ The organ function level must meet the requirements on the premise that blood transfusion is not allowed within 14 days before the screening period, and no cell growth factor drugs are allowed;

⁃ A serum pregnancy test must be performed within 7 days before the start of treatment for premenopausal fertile women, and the result must be negative and must not be lactating; All enrolled patients should take adequate barrier contraception during the entire treatment cycle and for 6 months after the end of treatment.