This is a randomized, multicenter, multinational, double-blind, integrated pharmacokinetics (PK) and efficacy similarity study to compare the PK, efficacy, safety, and immunogenicity of MB12 versus Keytruda® in combination with pemetrexed-platinum chemotherapy as first-line treatment in patients with metastatic non-squamous NSCLC.

Inclusion Criteria:

1. Adult male/female patients ≥18 years old at the time of signing the informed consent form (ICF).
2. Histologic or cytologic diagnosis of advanced NSCLC, stage IV (defined by the 8th edition of the Tumor Node Metastasis [TNM] classification), with no EGFR sensitizing (activating) mutation or ALK translocation, and who have not received prior systemic treatment for metastatic NSCLC. In those patients in whom the pleural or pericardial effusion is the only location of metastatic disease, confirmation of its malignant etiology is required.
3. At least 1 radiographically measurable lesion according to response evaluation criteria in solid tumors (RECIST) 1.1.
4. Known status of PD-L1 expression.
5. Performance based on the Eastern Cooperative Oncology Group (ECOG) performance status ≤1.
6. Adequate hepatic, renal, hematologic, endocrine, and coagulation function.

Exclusion Criteria:

1. Predominantly squamous cell histology NSCLC. Mixed tumors will be categorized by the predominant cell type; if small cell elements are present, the patient is not eligible.
2. Known history of central nervous system metastases and/or carcinomatous meningitis.
3. Prior anti-programmed cell death (PD)-1, anti-PD-L1, anti-PD-L2, anti-CD137, or anti-cytotoxic T lymphocyte associated protein (CTLA)-4 therapy (including ipilimumab or any other antibody or drug that specifically targets co-stimulation of T-cells or immune checkpoints).
4. Major surgery within 3 weeks of the first dose of study treatment.
5. Active autoimmune disease that has required systemic treatment in the last 2 years.
6. Contraindication and/or intolerance to the administration of pembrolizumab or known sensitivity to any component of pembrolizumab.
7. Has a known sensitivity to any component of cisplatin, carboplatin, or pemetrexed.