Key Inclusion Criteria:  Patients must have histologically confirmed unresectable Stage III or metastatic Stage IV NSCLC and measurable disease by RECIST v1.1. Note: Patients in Cohort 1 do not have to have measurable disease. Patients in Cohorts 2 and 4 must be able to tolerate additional anti-PD-1 therapy (i.e., did not permanently discontinue anti-programmed death protein 1 (PD-1) / programmed death ligand 1 (PD-L1) therapy due to toxicity) and must have recovered to stage 1 or 0 from any previous PD-1/PD-L1-related toxicity or be on a stable hormone substitute therapy. Patients in Cohorts 2 and 3 must have an Eastern Cooperative Oncology Group performance status (ECOG-PS) ≤1. Patients in Cohort 1 and 4 with an ECOG-PS of 0-2 are eligible.  Cohort-specific inclusion criteria:  Cohort 1:  Patients' prior therapy must have included at least a PD-1/PD-L1 inhibitor and a platinum-based chemotherapy regimen as well as one other line of systemic therapy (except if a patient is not candidate for a platinum-based chemotherapy and/or PD-1/PD-L1 inhibitor and/or another line of systemic therapy).  Cohort 2:  Patients must present with PD-L1 expression of tumor proportion score (TPS) ≥50% in tumor cells (as determined locally prior to inclusion in this trial).  Patients must present with progressive disease either  in the advanced or metastasized stage of NSCLC: while on a PD-1/PD-L1 inhibitor therapy or within 6 months of termination of this treatment as first-line treatment. Or be refractory to ongoing adjuvant therapy with a PD-1/PD-L1 inhibitor that has been given for at least 3 months in monotherapy (i.e., after an initial combination therapy) before being enrolled into this trial.  Cohort 3:  Patients' prior therapy must have included at least a PD-1/PD-L1 inhibitor and a platinum-based chemotherapy regimen (except if a patient is not candidate for a platinum-based chemotherapy and/or PD-1/PD-L1 inhibitor).  Cohort 4:  Patients' who are not candidates for chemotherapy as first-line treatment for the advanced or metastasized stage of NSCLC may be enrolled if presenting with PD-L1 expression: TPS ≥1% in tumor cells.  Key Exclusion Criteria:  Ongoing active systemic treatment against NSCLC. Presence of a driver mutation for which approved target therapies are available. Ongoing or recent evidence (within the last 5 years) of significant autoimmune disease that required treatment with systemic immunosuppressive treatments which may suggest risk for immune-related adverse events. Note: Patients with autoimmune-related hyperthyroidism, autoimmune-related hypothyroidism who are in remission, or on a stable dose of thyroid-replacement hormone, vitiligo, or psoriasis may be included. Current evidence of new or growing brain or spinal metastases during screening. Patients with leptomeningeal disease are excluded. Patients with known brain or spinal metastases may be eligible if they: had radiotherapy or another appropriate therapy for the brain or spinal bone metastases, AND have no neurological symptoms that can be attributed to the current brain lesions, AND have stable brain or spinal disease on the computed tomography (CT) or magnetic resonance imaging (MRI) scan within 4 weeks before signing the informed consent (confirmed by stable lesions on two scans at least 4 weeks apart), AND do not require steroid therapy for the treatment of brain or spinal metastases within 14 d before the first dose of trial treatment. Note: Spinal bone metastases (i.e., of the vertebrae) are allowed, unless imminent fracture or cord compression is anticipated. Systemic immune suppression: Current use of chronic systemic steroid medication (≤5 mg/day prednisolone equivalent is allowed); patients using physiological replacement doses of prednisone for adrenal or pituitary insufficiency are eligible. Other clinically relevant systemic immune suppression within the last 3 months before trial enrollment. Known history of seropositivity for human immunodeficiency virus (HIV) with CD4+ T-cell (CD4+) counts <350 cells/µL and with a history of acquired immunodeficiency syndrome (AIDS)-defining opportunistic infections. Prior splenectomy.