Inclusion Criteria:
1. 18 years old ≤ 75 years old; Both male and female;
2. ECOG 0-1;
3. Histologically or cytologically confirmed non-small cell lung cancer;
4. Progression with brain metastasis after previous first-line anti-tumor therapy;
5. Requirements for brain metastases: ① measurable brain metastases without radiotherapy; ②SRS/FSRT: the maximum tumor volume of brain metastases was less than 10cm3, the single diameter was less than 3cm, and the total volume of brain metastases involved was less than 15 cm3.
6. Response to previous checkpoint inhibitor therapy on the initial response assessment;
7. If a metastatic lesion of the head has been irradiated, the cumulative radiation dose does not exceed the tolerated dose to all structures.
8. For patients with measurable CNS lesions, the longest diameter on MRI images is ≥10mm, which is suitable for repeated and accurate measurement.
9. Subjects were evaluated for all extracranial disease sites (e.g., by computed tomography (CT) scan and bone scan or positron emission tomography (PET-CT) within 14 days before the first dose.
10. Subjects had to have a baseline brain MRI scan within 14 days before the first dose of medication.
11. Estimated survival time \> 12 weeks.
12. Participants of childbearing age must agree to use effective contraception during the trial; In women of childbearing age, a serum or urine pregnancy test must be negative.
13. Patients who are not lactating.
14. Have definite and good organ functions:
15. Provide informed consent voluntarily, and be willing and able to comply with the follow-up, treatment, laboratory testing, and other study requirements specified in the study schedule.
Exclusion Criteria:
Subjects who meet any of the following criteria are not eligible to participate in the study:
1. Experienced grade 3-4 intracranial toxicity (pituitary or central nervous system toxicity);
2. No measurable intracranial metastatic lesions without radiotherapy;
3. Meningeal metastasis;
4. If receiving chemotherapy or targeted therapy, the washout period should not exceed 3 weeks; if receiving brain metastasis resection, the washout period should not exceed 2 weeks;
5. Have significant autoimmune diseases
6. Prior treatment with a cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitor.
7. Previous (within 5 years) or concurrent other malignant tumors
8. History of anaphylaxis to any monoclonal antibody and/or study drug component.
9. A history of or current noninfectious pneumonia/interstitial lung disease requiring systemic glucocorticoids.
10. Serious infection within 4 weeks before the first dose.
11. Known history of allogeneic organ transplantation and allogeneic hematopoietic stem cell transplantation.
12. Subjects required systemic treatment with corticosteroids (\>10mg prednisone equivalent per day) or other immunosuppressive drugs within 14 days before taking the study drug.
13. Patients with clinically significant cardiovascular disease
14. Enroll in another clinical study at the same time, unless it is an observational, noninterventional clinical study or a follow-up of an interventional study.
15. Received live vaccine within 30 days before the first dose, or planned to receive live vaccine during the study.
16. Known history of mental illness, substance abuse, alcohol or drug abuse.
17. Pregnant or lactating women.
18. The presence of any past or current medical conditions, treatments, or laboratory abnormalities may confound the results of the study, interfere with the full participation of the subject in the study, or may not be in the best interest of the subject to participate in the study.
