First Line Therapy for Extensive SCLC Patients, Treated with Chemo+Keytruda Followed by Keytuda+Trodelvy

Inclusion Criteria:

1. Male/female participants who are at least 18 years of age on the day of signinginformed consent with histologically or cytologically confirmed diagnosis of ES SCLCwill be enrolled in this study.

2. The participant has not been previously treated with systemic therapy for ES SCLC (i.e., the disease is treatment naïve). Note: Participants previously treated for limited SCLC will be allowed withdisease-free survival (DFS) of 6 months after completion of all treatment.

3. Participants who have AEs due to previous anticancer therapies must have recoveredto ≤Grade 1 or baseline. Participants with endocrine-related AEs who are adequatelytreated with hormone replacement or participants who have ≤Grade 2 neuropathy areeligible.

4. The participant (or legally acceptable representative if applicable) provideswritten informed consent for the trial.

5. Has measurable disease based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. Lesions situated in a previously irradiated area are consideredmeasurable if progression has been demonstrated in such lesions.

6. Archival tumor tissue sample or newly obtained [core, incisional or excisional]biopsy of a tumor lesion not previously irradiated has been provided. Note:Participants with asymptomatic brain metastases will be eligible. Formalin-fixed,paraffin embedded (FFPE) tissue blocks are preferred to slides. Newly obtainedbiopsies are preferred to archived tissue.

7. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. Evaluationof ECOG is to be performed within 3 days prior to the first dose of studyintervention.

8. Life expectancy >3 months.

9. Has adequate organ function as defined in the following table (Table 2). Specimensmust be collected within 10 days prior to the start of study intervention.

10. A female participant is eligible to participate if she is not pregnant (refer to theClinical Trials Facilitation and Coordination Group [CTFG] "Recommendations relatedto contraception and pregnancy testing in clinical trials", Appendix 5), notbreastfeeding, and at least one of the following conditions applies:

11. Not a woman of childbearing potential (WOCBP) as defined by CTFGRecommendations (Appendix 5) or

12. A WOCBP who agrees to follow the contraceptive guidance per CTFGRecommendations (Appendix 5) during the treatment period and for at least 120days (corresponding to time needed to eliminate any study treatments) after thelast dose of study treatment.

Exclusion Criteria:

1. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti PD L2 agent orwith an agent directed to another stimulatory or co-inhibitory T-cell receptor (e.g., CTLA-4, OX 40, CD137).

2. Has received prior systemic anti-cancer therapy including biologic agents orinvestigational agents or an investigational device within 4 weeks prior totreatment initiation.

3. Has received prior radiotherapy, chemotherapy, or targeted small molecule therapywithin 2 weeks of start of study intervention and have not recovered from AEs at thetime of study entry (i.e., ≥Grade 2 is considered not recovered), orradiation-related toxicities requiring corticosteroids. Note: Two weeks or fewer ofpalliative radiotherapy for non-central nervous system (CNS) disease is permitted.The last radiotherapy treatment must have been performed at least 7 days before thefirst dose of study intervention.

4. Have not recovered (i.e., ≥Grade 2 is considered not recovered) from AEs due to apreviously administered agent. Note: participants with any grade neuropathy or alopecia are an exception to thiscriterion and will qualify for the study.

5. Have previously received topoisomerase 1 inhibitors.

6. Has received a live vaccine or live-attenuated vaccine within 30 days before thefirst dose of study intervention. Administration of killed vaccines is allowed. (Refer to Section 5.5 for information on COVID-19 vaccines).

7. Use of other investigational drugs (drugs not marketed for any indication) within 28days or 5 half-lives (whichever is longer) of first dose of study drug.

8. Has a known hypersensitivity to any of the study treatments, their metabolites, orformulation excipients.

9. Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form ofimmunosuppressive therapy within 7 days prior to the first dose of study drug.

10. Known additional malignancy that is progressing or has required active treatmentwithin the past 3 years. Note: Participants with basal cell carcinoma of the skin,squamous cell carcinoma of the skin or carcinoma in situ, excluding carcinoma insitu of the bladder, that have undergone potentially curative therapy are notexcluded. Participants with low-risk early-stage prostate cancer (T1-T2a, Gleasonscore ≤6, and PSA <10 ng/mL) either treated with definitive intent or untreated inactive surveillance with stable disease are not excluded.

11. Has known active CNS metastases and/or carcinomatous meningitis. Participants withpreviously treated brain metastases may participate provided they are radiologicallystable, i.e. without evidence of progression for at least 4 weeks by repeat imaging (note that the repeat imaging should be performed during study screening),clinically stable and without requirement of steroid treatment for at least 14 daysprior to first dose of study intervention.

12. Has active autoimmune disease that has required systemic treatment in the past 2years except replacement therapy (e.g., thyroxine, insulin, or physiologiccorticosteroid).

13. Has a history of (non-infectious) pneumonitis/interstitial lung disease thatrequired steroids or has current pneumonitis/interstitial lung disease.

14. Has an active infection requiring systemic therapy.

15. Has an active chronic inflammatory bowel disease (ulcerative colitis, Crohn'sdisease) or gastrointestinal perforation within 6 months of enrollment.

16. Have a history of, or active hepatitis B virus (HBV) or hepatitis C virus (HCV). Note: Testing for Hepatitis B or C is not required unless mandated by local healthauthority.

17. Has not adequately recovered from major surgery or has ongoing surgicalcomplications.

18. Has a history or current evidence of any condition, therapy, or laboratoryabnormality or other circumstance that might confound the results of the study,interfere with the participant's participation for the full duration of the study,such that it is not in the best interest of the participant to participate, in theopinion of the treating investigator.

19. Has known psychiatric or substance abuse disorders that would interfere withcooperation with the requirements of the trial.

20. Is pregnant or breastfeeding or expecting to conceive or father children within theprojected duration of the study, starting with the screening visit through 120 daysafter the last dose of trial treatment.

21. Has had an allogenic tissue/solid organ transplant.

22. History of HIV infection. Note: HIV testing is not required unless mandated by localhealth authority.