Inclusion Criteria:

          -  Age ≥ 18 years with histologically- or cytologically-confirmed, extensive-stage,
             chemotherapy-naïve SCLC

          -  DLL3-expressing SCLC based on central immunohistochemistry (IHC) assessment. Positive
             is defined as staining in ≥75% of tumor cells.

          -  Eastern Cooperative Oncology Group performance status of 0 or 1.

          -  Minimum life expectancy of at least 12 weeks.

          -  Recovery to Grade 1 of any clinically significant toxicity (excluding alopecia) prior
             to initiation of study drug.

          -  Satisfactory laboratory parameters within defined parameters (ANC, platelet count, Hb,
             total bilirubin, ALT, AST and GFR)

          -  Subjects with a history of CNS metastases must have completed definitive treatment
             prior to first dose of study treatment, off or on a stable dose of corticosteroids

          -  Use of effective contraception method during and for 1 year following study drug
             dosing if female of childbearing potential or sexually active male

        Exclusion Criteria:

          -  Prior systemic chemotherapy, small molecule inhibitors, immune checkpoint inhibitors,
             other monoclonal antibodies, antibody-drug conjugates, radioimmunoconjugates, T-cell
             or other cell-based or biologic therapies, or any other anticancer therapy for the
             treatment of (limited or extensive) SCLC.

          -  Any significant medical condition, that, in the opinion of the investigator or
             sponsor, may place the subject at undue risk from the study.

          -  Documented history of a cerebral vascular, unstable angina, myocardial infarction, or
             cardiac symptoms consistent with New York Heart Association (NYHA) Class III-IV within
             6 months prior to their first dose of study drug.

          -  Recent or ongoing serious infection.

          -  Women who are pregnant or breastfeeding.

          -  History of another invasive malignancy that has not been in remission for at least 3
             years. Exceptions: nonmelanoma skin cancer, curatively treated localized prostate
             cancer, and cervical cancer in situ on biopsy or squamous intraepithelial lesion on
             PAP smear.

          -  Prior exposure to a pyrrolobenzodiazepine (PBD)-based drug, or known hypersensitivity
             to rovalpituzumab tesirine or excipient contained in the drug formulation