This research study is a multicentre phase Ⅰb/Ⅱ Study to evaluate the efficacy and safety of the combination of Fluzoparib (SHR-3162) and temozolomide with or without SHR-1316 in small cell lung cancer

Inclusion Criteria:

1. Subjects who have recurrent small cell lung cancer confirmed by histology or cytology.
2. Failed one prior line of platinum-based chemotherapy.
3. Subjects must have measurable disease, at least one lesion, by Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) per RECIST 1.1 criteria (within 28 days prior to administration of study treatment) ;
4. Freshly acquired samples or archived specimens within 12 months before randomization must be provided.
5. Eastern Cooperative Oncology Group (ECOG) performance status of 0-1.
6. Participant must have a life expectancy ≥ 12 weeks.

Exclusion Criteria:

1. Active or untreated central nervous system (CNS) metastases.
2. Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures.
3. History of autoimmune disease.
4. Positive test result for human immunodeficiency virus (HIV).
5. Active hepatitis B or hepatitis C.
6. Severe infections.
7. Subjects with a condition requiring systemic treatment with either corticosteroids (>10 mg daily prednisone equivalent) or other immunosuppressive medications within 14 days of first administration of study treatment.
8. Significant cardiovascular disease.
9. History or current evidence of any condition, therapy, or laboratory abnormality that might confound the results of the study, interfere with the subject's participation for the full duration of the study, or is not in the best interest of the subject to participate, in the opinion of the treating investigator.