Inclusion Criteria:

          -  Subject has histologic or cytologic confirmation of metastatic NSCLC. Subjects must
             have a TPS score available as determined by an FDA approved test. Subject has stable
             disease or disease progression and is being treated with pembrolizumab therapy as
             standard of care by the Investigator.

          -  Subject is male or female and at least 18 years of age.

          -  Subject has at least 1 measurable lesion per RECIST v1.1 criteria by computed
             tomography (CT) scan or magnetic resonance image (MRI).

          -  Subject provides consent for fresh paired tumor biopsy samples to be obtained at
             screening and after 4 weeks of treatment (not required for run-in cohort or expansion
             of run-in cohort).

          -  Subject has a life expectancy of at least 12 weeks

          -  Subject has adequate organ function as determined by the following laboratory values:

               -  ANC* ≥ 1500/mm³ (≥ 1.5 x 10^9/L)

               -  Platelets* ≥ 100,000/mm³ (≥ 100 x 10^9/L)

               -  Lymphocytes* ≥ 500/mm³ (≥ 0.5 x 10^9/L)

               -  Hemoglobin* ≥ 9.0 g/dL

               -  Serum Creatinine or Creatinine Clearance** ≤ 1.5 x ULN, > 50 mL/min

               -  Total Serum Bilirubin ≤ 1.5 x ULN (< 3.0 mg/dL if subject has Gilbert's syndrome)

               -  Liver Transaminases (ALT/AST) ≤ 2.5 x ULN, ≤ 5.0 x ULN if liver metastases
                  present

                    -  (* = without ongoing growth factor or transfusion support)

                    -  (** = calculated by Cockcroft and Gault's formula)

                    -  (ALT = alanine aminotransferase, AST = aspartate aminotransferase, ULN =
                       upper limit of normal)

        Exclusion Criteria:

          -  Subjects may not have genomic aberrations such as ALK, EGFR, or BRAF for which there
             are FDA-approved targeted therapies available. Subjects may not have ROS1 aberration
             in accordance with the pembrolizumab label.

          -  Subject has received an investigational drug in the 28 day period before the first
             dose of study drug (or within 5 half-lives if longer) or is currently participating in
             another interventional clinical trial.

          -  Subject has known symptomatic brain metastases or leptomeningeal involvement as
             assessed by CT scan or MRI. Subjects with stable asymptomatic brain metastases or
             leptomeningeal disease are eligible provided that they have not required new
             treatments for this disease in a 28 day period before the first dose of study drug,
             and anticonvulsants and steroids have not been administered for a period of 2 weeks
             prior to the first dose of study drug.

          -  Subject has not recovered from adverse reactions to prior cancer treatment or
             procedures (surgery, chemotherapy, immunotherapy, radiation therapy) to CTCAE Grade 2
             or better.

          -  Subject has a previous (within 5 years) or current malignancy other than the target
             cancer with the exception of curatively treated local tumors such as carcinoma in situ
             of the breast or cervix, basal or squamous cell carcinoma of the skin, or prostate
             cancer with Gleason Grade < 6 and prostate-specific antigen within normal range.