Double-blind Study to Evaluate the PK, Efficacy, Safety and Immunogenicity of MB12 Versus Keytruda® in Stage IV NSCLC

This is a randomized, multicenter, multinational, double-blind, and parallel-group study to evaluate the PK, efficacy, safety and immunogenicity of MB12 (proposed pembrolizumab biosimilar) versus Keytruda® in subjects with newly diagnosed stage IV non-squamous NSCLC. This study is planned to be conducted in approximately 48 sites in 7 countries, a total of 174 subjects will be enrolled. Eligible subjects will be randomized in a 1:1 ratio to receive MB12 or Keytruda® at a dose of 200 mg every 3 weeks. Subjects will be stratified by gender (male versus female) and ECOG status (0 versus 1) as both factors are considered to have the potential to influence PK properties of pembrolizumab to some extent. The study will consist of 2 periods defined as follows: * Main Study Period from Screening up to Cycle 6 included. * Extended Treatment Period from Cycle 7 up to Week 52 for those subjects who demonstrate clinical benefit from the treatment (complete response \[CR\], partial response \[PR\], and stable disease \[SD\]). They will continue treatment until disease progression, intolerance to the study drug, treatment discontinuation for other reason, or up to Week 52, whichever occurs first. A Data Safety Monitoring Board (DSMB) will assess the safety data periodically and will recommend to the sponsor whether to continue, modify, or stop the trial on the basis of safety considerations. After the first 10 subjects have received at least 2 cycles of treatment, the DSMB will review the accumulated safety data, and the first meeting will take place. Subsequent meetings will be performed as per the DSMB charter.