Main Inclusion Criteria:

          1. Written informed consent and any locally required authorization obtained from the
             subject prior to performing any protocol-related procedures, including screening
             evaluation

          2. Age 18 years or older

          3. Body weight ≥ 35 kg

          4. Subjects must have histologically or cytologically documented NSCLC who present with
             locally advanced, unresectable, Stage III disease

          5. Subjects must have completed, without progressing, definitive cCRT within 42 days
             prior to being randomized into the study:

          6. Provision of tumor tissue sample, when available, from original diagnosis obtained
             before initiation of chemoradiotherapy

          7. Life expectancy ≥ 12 weeks

          8. Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1

          9. Subjects must have at least one previously irradiated tumor lesion that can be
             measured by RECIST v1.1

        Main Exclusion Criteria:

          1. Mixed small cell and non-small cell lung cancer histology

          2. Current or prior use of immunosuppressive medication within 14 days before the first
             dose of study drug.

          3. Prior exposure to any anti-PD1, anti-PD-L1, or anti-CTLA4 antibody for treatment of
             NSCLC

          4. Subjects with history of ≥ Grade 2 pneumonitis from prior chemoradiation therapy

          5. Subjects with a history of venous thrombosis within the past 3 months

          6. Subjects with history of myocardial infarction, transient ischemic attack, or stroke
             in the past 6 months

          7. Congestive heart failure

          8. Active or prior documented autoimmune or inflammatory disorders

          9. History of active primary immunodeficiency

         10. Active infection including tuberculosis, hepatitis B, hepatitis C, or human
             immunodeficiency virus (HIV)

         11. History of allogenic organ transplantation

         12. QTcF interval ≥ 470 ms

         13. History of another primary malignancy

         14. Concurrent enrollment in another therapeutic clinical study or during the follow-up
             period of an interventional study. Enrollment in observational studies will be allowed

         15. Females who are pregnant, lactating, or intend to become pregnant during their
             participation in the study