CTLA4 and non-small cell lung carcinoma: For NSCLC patients with low PD-L1 expression level who are not willing to receive chemotherapy, the CheckMate 227 trial demonstrated that first-line treatment with nivolumab plus ipilimumab that was a monoclonal antibody inhibiting cytotoxic T-lymphocyte antigen-4 (CTLA-4) resulted in a longer duration of overall survival than chemotherapy alone without long-term safety concerns, regardless of PD-L1 expression level.