Vactosertib in Combination With Pembrolizumab for PD-L1 Positive Non-small Cell Lung Cancer (NSCLC) Subjects

Inclusion Criteria:

1. Have a histologically- or cytologically-documented NSCLC advanced or stage IV lung cancer
2. Have confirmation that EGFR, ALK, BRAF, ROS1-directed therapy is not indicated
3. Have measurable disease based on RECIST 1.1
4. PD-L1 expression is ≥1% as determined by the PD-L1 IHC 22C3 pharmDx assay
5. Have a life expectancy of at least 3 months.
6. ECOG 0 or 1
7. Subjects must be able to swallow tablets and absorb vactosertib.
8. Have adequate organ function as indicated by the following laboratory values in

Exclusion Criteria:

1. Is currently participating in a study of an investigational agent
2. Has received prior systemic cytotoxic chemotherapy for metastatic disease/ antineoplastic biological therapy /Had major surgery / radiation therapy to the lung
3. Has received a live vaccine within 30 days prior to the first dose of study drug.
4. Is taking prohibited medications
5. Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy
6. Has known active central nervous system (CNS) metastases and/or carcinomatous meningitis.
7. Had a severe hypersensitivity reaction to treatment with another mAb previously.
8. Has severe hypersensitivity to vactosertib and/or any of its excipients