Inclusion Criteria:

          -  Subject has provided informed consent prior to initiation of any study-specific
             activities/procedures

          -  Age greater than or equal to 18 years old at the time of signing the informed consent

          -  Histologically or cytologically confirmed Small Cell Lung Cancer (SCLC):

          -  Part A, C, D, E and F: RR SCLC who progressed or recurred following platinum-based
             regimen;

          -  Part B: ED SCLC with ongoing clinical benefit (stable disease [SD], partial response
             [PR], or complete response [CR]) following no more than 6 cycles of first-line
             platinum-based chemotherapy with the last dose of chemotherapy greater than or equal
             to 28 days prior to the study day 1 (first-line consolidation setting)

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0-2

          -  Subjects with treated brain metastases are eligible provided they meet defined
             criteria

          -  Adequate organ function as defined in protocol

        Exclusion Criteria:

          -  History of other malignancy within the past 2 years prior to first dose of AMG 757
             with exceptions

          -  Major surgery within 28 days of first dose AMG 757

          -  Untreated (includes new lesions or progression in previously treated lesions) or
             symptomatic brain metastases and leptomeningeal disease

          -  Prior anti-cancer therapy: at least 28 days must have elapsed between any prior
             anti-cancer therapy and first dose of AMG 757

        Exceptions:

          -  Subjects who received conventional chemotherapy are eligible if at least 14 days have
             elapsed and if all treatment-related toxicity has been resolved to Grade less than or
             equal to 1

          -  Prior palliative radiotherapy must have been completed at least 7 days before the
             first dose of AMG 757

          -  Subjects who experienced severe, life-threatening or recurrent (Grade 2 or higher)
             immune-mediated adverse events or infusion-related reactions including those that lead
             to permanent discontinuation while on treatment with immune-oncology agents.

          -  Has evidence of interstitial lung disease or active, non-infectious pneumonitis

          -  Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any
             other form of immunosuppressive therapy within 7 days prior to the first dose of AMG
             757

          -  Part C only: history of solid organ transplantation or active autoimmune disease that
             has required systemic treatment within the past 2 years