• Age ≥ 18 years, male or female;

• Patients with histologically and/or cytologically confirmed small cell lung cancer;

• Disease progression (CTFI ≥ 30 days and ≤ 6 months) occurred after at least 4 cycles of first-line etoposide + platinum two-drug chemotherapy-based treatment, regardless of whether the primary tumor was treated with radiotherapy; the stage of patients with limited stage SCLC should meet more than T1-2, N0, or not suitable for surgery;

• At least one evaluable lesion (according to RECIST 1.1 criteria);

• Expected survival time ≥ 3 months;

• Eastern Cooperative Oncology Group (ECOG) score \< 2;

• Patients who received no liver metastasis; or the number of liver metastases was ≤ 3 and the longest diameter of a single lesion was ≤ 1.5 cm; or although the longest diameter of a single lesion was \> 1.5 cm, the imaging was stable for at least 3 weeks after local treatment control;

• Patients with brain metastasis at baseline should meet all the following conditions: lesions not involving the brainstem, the number of brain metastases ≤ 2 (but patients with only intracranial target lesions should be excluded), imaging stability for at least 3 weeks after local treatment control, and no application of dehydration drugs and hormones before screening,Without any symptoms of brain metastasis;

• Organ function meeting the following criteria at screening: a.Blood routine: neutrophil (ANC) ≥ 1.5 × 109/L, platelet (PLT) ≥ 100 × 109/L, hemoglobin (Hb) ≥ 90 g/L; b.Liver function: total bilirubin (TBIL) ≤ 1.0 × upper limit of normal (ULN); aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.0 × ULN; if liver metastases, AST and ALT ≤ 3 × ULN; serum albumin ≥ 30 g/L; c.Renal function: serum creatinine ≤ 1.5 × ULN or creatinine clearance ≥ 40 mL/min; d.Coagulation function: Prothrombin time - international normalized ratio (PT-INR) \< 1.5;

⁃ Has fully understood and voluntarily signed a written informed consent form for this study and is able to comply with the requirements and restrictions listed in the informed consent form;

⁃ Female subjects of childbearing potential and male subjects with partners of childbearing potential agree to use reliable contraceptive measures during the study and within 6 months after the infusion of study drug.