Inclusion Criteria:

          1. Subjects scheduled to be treated with (definitive or adjuvant) radiation therapy in
             combination with chemotherapy once daily for Stage 3A/3B or post-operative Stage 2B
             NSCLC or limited stage SCLC

          2. Treatment plan for subjects show that 5 cm of the esophagus for at least one surface,
             is included in the 60 Gy isodose volume. Dose volume histograms show esophagus dose
             exposure meet V38>30% and/or V60>20%

          3. Age 18 years or older

          4. ECOG performance status ≤ 2

          5. Adequate hematologic, renal and liver function

          6. Use of highly effective contraception

        Exclusion Criteria:

          1. Metastatic disease

          2. Prior radiation therapy to the region of the study cancer

          3. Subjects not receiving chemotherapy

          4. Grade 2 or greater esophagitis at baseline

          5. Inability to provide information in the electronic symptom-reporting device

          6. Receiving any approved or investigational immunotherapy, targeted therapy, hormone
             therapy, or biologic therapy

          7. Participation in another clinical trial or use of another investigational agent within
             30 days of first does of GC4419

          8. Malignant tumors other than the current lung cancer within the last 5 years

          9. Previous diagnosis of pneumonitis

         10. Untreated, active infectious disease requiring systemic anti-infective therapy

         11. Untreated HIV or active hepatitis B/C

         12. Females who are pregnant or breastfeeding

         13. Known allergies or intolerance to chemotherapy and similar platinum-containing
             compounds

         14. Requirement for concurrent treatment with nitrates or other drugs that may create a
             risk for a precipitous decrease in blood pressure

         15. Clinically significant heart disease