Study of Platinum Plus Etoposide With or Without Tislelizumab in Participants With Untreated Extensive-Stage Small Cell Lung Cancer

Key Inclusion Criteria

• Age≥18 years old, male or female, signed Informed Consent Form (ICF).
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
• Histologically or cytologically confirmed ES-SCLC
• No prior systemic treatment for ES-SCLC
• Adequate hematologic and end organ function

Key Exclusion Criteria

• Active leptomeningeal disease or uncontrolled, untreated brain metastasis;
• Prior therapy with an antibody or drug against immune checkpoint pathways, including but not limited to, anti program death receptor-1 (anti-PD-1), anti-PD-L1, or anti cytotoxic T lymphocyte associated antigen 4 (anti CTLA-4) antibody;
• Was administered a live vaccine ≤ 4 weeks before randomization;
• Active autoimmune diseases or history of autoimmune diseases that may relapse
• Any condition that required systemic treatment with either corticosteroids or other immunosuppressive medication ≤ 14 days before randomization;
• With a history of interstitial lung disease, non-infectious pneumonitis, or uncontrolled systemic diseases;
• Severe chronic or active infections requiring systemic antibacterial, antifungal or antiviral therapy within 2 weeks prior to randomization, including but not limited to tuberculosis infection;
• Participant with untreated hepatitis B virus (HBV)/hepatitis C virus (HCV), or a known history of HIV infection;
• Participants with toxicities (as a result of prior anticancer therapy) which have not recovered to baseline or stabilized at the time of randomization;
• Clinically significant pericardial effusion, or Clinically uncontrolled pleural effusion

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply.