• All subjects or legal representatives must sign the informed consent form approved by the Ethics Committee in writing prior to the start of any screening procedures;

• Age ≥ 18 years, male or female;

• Histologically or cytologically confirmed small cell lung cancer patients who have recurrent or advanced disease after at least two lines of systemic regimen (including first-line platinum-based therapy, second-line monotherapy or other therapies \*);

• At least one measurable tumor lesion according to RECIST 1.1 \*\*;

• Expected survival time of at least 12 weeks;

• ECOG (PS) score of 0 to 2;

• Subject has adequate organ and bone marrow function and meets the following laboratory criteria:

‣ Blood routine test (without red blood cell or platelet transfusion or hematopoietic factor drug correction within 14 days before screening): absolute neutrophil count (ANC) ≥ 1.5 × 10\^9/L (1500/mm3), platelets ≥ 80 × 10\^9/L; hemoglobin ≥ 9.0 g/dL;

⁃ Liver function: serum total bilirubin ≤ 1.5 × ULN (upper limit of normal), except for patients with Gilbert 's syndrome (persistent or recurrent hyperbilirubinemia, manifested as unconjugated bilirubin elevation in the absence of hemolysis or pathological evidence of liver); alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 2.5 × ULN for patients without liver metastasis, and ALT and AST ≤ 5 × ULN for patients with liver metastasis;

⁃ Renal function: Serum creatinine ≤ 1.5 × ULN and estimated standard cendogenous creatinine clearance rate ≥ 60 ml/min by Cockcroft-Gault formula, Ccr (ml/min) = \[(140-age) × body weight (kg)\]/\[72 × Scr (mg/dl)\], calculated for females × 0.85;

⁃ Coagulation function: international normalized ratio (INR) ≤ 1.5;

⁃ Left ventricular ejection fraction (LVEF) \> 50% at screening. 8.1) Female: For female subjects of childbearing potential, they must have a negative serum pregnancy test within 7 days prior to enrollment and agree to use a medically approved method of contraception (condom, sponge, gel, diaphragm, IUD, oral or injectable contraceptive, subcutaneous implant, etc.) during and for 3 months after treatment; they must be non-pregnant and lactating. Female subjects are considered fertile if they are menopausal but have not reached post-menopausal status (menopause of 12 consecutive months or more, with no cause other than menopause) and have not undergone sterilization (removal of ovaries and/or uterus). Their sexual partner agrees to use a medically licensed method of contraception during the subject's treatment and for 3 months after completion; 2) Males: surgical sterilization or agreement to use medically licensed contraception during and for 3 months after the end of treatment; their sexual partners agree to use medically licensed contraception during and for 3 months after the end of the subject's treatment;

∙ 9\. Capable and willing to comply with protocol requirements during the study and subsequent procedures.