• Signed Informed Consent Form

• Male or female, 18 years of age or older

• ECOG performance status of 0 or 1

• Histologically or cytologically confirmed ES-SCLC (per the Veterans Administration Lung Study Group (VALG) staging system

• No prior treatment for ES-SCLC

• Patients with a history of treated asymptomatic CNS metastases are eligible, provided they meet all of the following criteria:

∙ Only supratentorial and cerebellar metastases allowed (i.e., no metastases

‣ to midbrain, pons, medulla or spinal cord)

‣ No ongoing requirement for corticosteroids as therapy for CNS disease

‣ No stereotactic radiation within 7 days

‣ No evidence of interim progression between the completion of CNS- directed therapy and the screening radiographic study.

‣ Patients with new asymptomatic CNS metastases detected at the screening scan must receive radiation therapy and/or surgery for CNS metastases. Following treatment, these patients may then be eligible without the need for an additional brain scan prior to randomization, if all other criteria are met.

• Measurable disease, as defined by RECIST v1.1 Previously irradiated lesions can only be considered as measurable disease if disease progression has been unequivocally documented at that site since radiation and the previously irradiated lesion is not the only site of disease.

• Adequate hematologic and end organ function, defined by the following laboratory results obtained within 14 days prior to randomization:

• ANC ≥ 1500 cells/μL without granulocyte colony-stimulating factor support; Lymphocyte count ≥ 500/μL; Platelet count ≥ 100,000/μL without transfusion; Hemoglobin ≥ 9.0 g/dL; Patients may be transfused to meet this criterion. INR or aPTT ≤ 1.5 × upper limit of normal (ULN) This applies only to patients who are not receiving therapeutic anticoagulation; patients receiving therapeutic anticoagulation should be on a stable dose. AST, ALT, and alkaline phosphatase ≤ 2.5 × ULN, with the following exceptions: Patients with documented liver metastases: AST and/or ALT ≤ 5 × ULN Patients with documented liver or bone metastases: alkaline phosphatase

• 5 × ULN. Serum bilirubin ≤ 1.25 × ULN Patients with known Gilbert disease who have serum bilirubin level ≤ 3 × ULN may be enrolled. Serum creatinine ≤ 1.5 × ULN

‣ Patients must submit a pre-treatment tumor tissue sample during the study. Any available tumor tissue sample can be submitted. The tissue sample may be submitted after enrollment.

⁃ For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods that result in a failure rate of \< 1% per year during the treatment period and for at least 90 days after the last dose of study treatment.