Study of Pegilodecakin (LY3500518) With Pembrolizumab Compared to Pembrolizumab Alone First-line Tx in Participants With Metastatic Non-Small Cell Lung Cancer

1. Participants must have histologically or cytologically confirmed WT NSCLC that is stage IV / metastatic or recurrent 2. Participants with tumor tissue high expression of PD-L1 as defined by Tumor Proportion Score (TPS) ≥ 50% 3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 4. Participants with measurable disease by spiral CT or MRI per RECIST v.1.1 criteria. 5. Participants that have completed prior radiotherapy or radiosurgery at least 2 weeks prior to randomization. 6. Participants must be naïve to therapy for the advanced stage of the disease. Previous neoadjuvant or adjuvant therapy is allowed for participants who successfully underwent complete radical surgery and ONLY if the last treatment was administered more than 12 months prior to the start of the trial treatment

1. Participants with active central nervous system (CNS) metastases or carcinomatous meningitis 2. Participants with any serious or uncontrolled medical disorder or active infection with the hepatitis virus or the human immunodeficiency virus (HIV) 3. Participants with Grade 1 (NCI-CTCAE v.4.03) toxicities attributed to prior anti-cancer therapy other than alopecia and fatigue prior to randomization 4. Participants that have received pembrolizumab 5. Participants with a history of severe hypersensitivity reactions to monoclonal antibodies 6. Pregnant or lactating women 7. Participants receiving any investigational agent within 28 days of first administration of trial treatment 8. Participants that have received therapy with anti-tumor vaccines or other immunostimulatory antitumor agents 9. Participants that have received therapy with anti-PD-1, anti-PD-L1, anti-PD-L-2, anti-CD-137, and/or anti CTLA-4 antibodies