A Study to Evaluate the Safety and Efficacy of Gocatamig (MK-6070) and Ifinatamab Deruxtecan (I-DXd) in Participants With Relapsed/Refractory Extensive-Stage Small Cell Lung Cancer (MK-6070-002)

Inclusion Criteria:

• Has histologically or cytologically confirmed SCLC that is extensive stage (definedas Stage IV (T any, N any, M1a/b/c) following at least 1 prior line of systemictherapy that included platinum-based chemotherapy

• Must be able to provide archival tumor tissue sample or fresh biopsy tissue sample

• Human immunodeficiency virus (HIV) infected participants must have well controlledHIV on antiretroviral therapy (ART)

Exclusion Criteria:

• Pleural effusion, pericardial effusion, or ascites requiring recurrent drainageprocedure

• History of interstitial lung disease (ILD)/pneumonitis irrespective of steroid useor has current or suspected pneumonitis/ILD that cannot be ruled out by imaging atscreening

• Has clinically severe pulmonary compromise resulting from intercurrent pulmonaryillnesses

• Active or history of immune deficiency with the exception of HIV-infectedparticipants with well controlled HIV on ART

• History within 6 months before the first dose of study intervention ofcoronary/peripheral artery bypass graft and/or any coronary/peripheral angioplastyor clinically significant cardiovascular disease such as myocardial infarction,symptomatic congestive heart failure (CHF) (New York Heart Association > class II),and/or uncontrolled cardiac arrhythmia

• History of arterial thrombosis (eg, stroke or transient ischemic attack) within 6months before the first dose of study intervention

• Active clinically significant infection requiring systemic therapy

• History of allogeneic tissue/solid organ transplant

• History of leptomeningeal disease

• Received prior radiotherapy within 2 weeks of start of study intervention, or hasradiation-related toxicities, requiring corticosteroids

• Receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily ofprednisone equivalent) or any other form of chronic immunosuppressive therapy within 7 days prior to the first dose of study intervention

• Known additional malignancy that is progressing or has required active treatmentwithin the past 3 years

• Untreated or symptomatic brain metastases

• Active viral hepatitis, defined as hepatitis A (hepatitis A virus immunoglobulin M [IgM] positive in the setting of associated signs/symptoms), hepatitis B (hepatitisB virus surface antigen [HbsAg] positive and/or detectable hepatitis B virus [HBV]deoxyribonucleic acid [DNA]), or hepatitis C (hepatitis C virus [HCV] antibodypositive and detectable HCV ribonucleic acid). Participants with HBV withundetectable viral load after treatment are eligible. Participants with HCV withundetectable virus after treatment are eligible.

• Part 1 only: Radiation therapy to the lung >30 Gy within 6 months before the startof study intervention

• Part 1 only: Abdominal radiation within 4 weeks before start of study intervention

• Part 1 only: Anticancer hormonal treatment (except luteinizing hormone-releasinghormone [LHRH]) within 2 weeks before start of study intervention

• Part 1 only: Systemic anticancer therapy (except antibody-based anticancer therapy)or investigational agents within 3 weeks or 5 half-lives, whichever is longer

• Part 1 only: Antibody-based cancer therapy within 3 weeks before start of studyintervention

• Part 1 only: Chloroquine/hydroxychloroquine within 2 weeks before start of studyintervention

• Part 1 only: Clinically significant corneal disease

• Part 1 only: Has other uncontrolled or significant protocol-specified cardiovasculardisease