NK Cells Plus ICI for SCLC Maintenance

Inclusion Criteria: * 1: Male or female, aged 18 years or above 2: ECOG score 0-2 3: metastatic or extensive-stage small cell lung cancer (SCLC) confirmed by histology or cytology, followed by 4 cycles of platinum-based doublet-chemotherapy with at least 2 cycles of immune checkpoint inhibitor plus chemotherapy. And stable disease (SD), partial response (PR), or complete response (CR) as assessed by imaging (RECIST1.1 criteria) after the last treatment. (The checkpoint inhibitors used were those recommended by the NCCN, ESMO, and CSCO guidelines for extensivestage SCLC, including but not limited to: Duvalumab, atezolizumab, slulizumab, adbelimumab, toripalimab, etc.) 4: After standard concurrent chemoradiotherapy, LS-SCLC could be enrolled in this study if sensitive relapse (relapse more than 6 months after the end of first-line treatment) progressed to extensive-stage (Ed) and met the inclusion criteria No.3; 5: At least 4 weeks after major surgery or trauma, and the wound must be completely healed; At least 1 week after minor surgical procedures or trauma (e.g., tissue biopsy or fine-needle aspiration); 6: Objective measurable lesions according to RECIST 1.1 criteria; 7: predicted survival time ≥1 year; 8: bone marrow function: ANC≥1.5×109/L, HB≥70 g/L (blood transfusion allowed), PLT≥80×109/L; 9: Liver function: ALT≤3×ULN, AST≤3×ULN, TBIL≤2×ULN (patients with liver metastasis ALT≤5×ULN, AST≤5×ULN, TBIL≤2×ULN) Child-Pugh score ≤7; Renal function: uric acid \<500 μmol/L, serum creatinine \<1.7 mg/dL, proteinuria ≤2+ or ≤2g/24h, glomerular filtration rate (GFR) ≥60 ml/min/1.73m2; 10: no history of autoimmune diseases or current autoimmune diseases; 11: The subjects voluntarily participated in the study, signed the informed consent form, communicated well with the investigators, and completed the study in accordance with the protocol. Exclusion Criteria: * 1:Participate in other clinical trials or use other research drugs or equipment within 4 weeks of the first treatment. 2: During the screening period and previous imaging evaluation, active or untreated CNS metastasis was found by CT scanning or MRI. Patients with asymptomatic CNS metastasis who had been treated in the past can participate in this study as long as they meet all the following criteria: corticosteroids are not needed to treat CNS diseases, and imaging examination has not found any progress from the end of CNS directional treatment to the screening period。 If new asymptomatic CNS metastases are found in patients during the screening period, they must undergo radiotherapy and/or CNS metastasis surgery 3: The effusion in the third space with clinical symptoms needs repeated drainage (for example, less than once every four weeks), such as pericardial effusion, pleural effusion and peritoneal effusion that are still uncontrollable after pumping or other treatments 4: Live vaccine was inoculated within 30 days before the first administration of the study drug. Live vaccines include but are not limited to measles, mumps, minute needle, chickenpox/herpes zoster, rabies, BCG, typhoid vaccine, etc. Seasonal influenza vaccine for injection is generally inactivated virus vaccine, which is allowed to be used. 5: The patient is known to have other malignant tumors, which are progressing or need active treatment in the past 3 years (except for in situ cancer or localized prostate cancer supplemented by PSA test) 6: Received major surgery, open surgical biopsy or severe traumatic injury 28 days before joining the group. 7: Clinically related or preexisting interstitial lung disease 8: Severe unhealed wound, ulcer or fracture 9: Suffering from autoimmune diseases requiring systemic treatment in the past 2 years 10: Unstable systemic concomitant diseases (active infection, moderate and severe chronic obstructive pulmonary disease, poorly controlled hypertension, unstable angina pectoris, congestive heart failure, myocardial infarction, cerebrovascular accident, pulmonary embolism or untreated history of Grade 3 deep vein thrombosis (DVT) within 6 months, serious mental disorder requiring drug control, liver, kidney or other metabolic diseases, neuropsychiatric diseases such as Alzheimer's disease). 11: According to the judgment of the researcher, there are patients with accompanying diseases that seriously endanger the safety of patients or affect the completion of the study.