A Study of Tislelizumab (BGB-A317) Versus Chemotherapy as Second Line Treatment in Participants With Advanced Esophageal Squamous Cell Carcinoma

Key Inclusion Criteria:

1. Histologically confirmed diagnosis of esophageal squamous cell carcinoma (ESCC)

2. Tumor progression during or after first-line treatment for advanced unresectable /metastatic ESCC

3. At least one measurable/evaluable lesion by Response Evaluation Criteria in SolidTumors (RECIST) v1.1

4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 prior torandomization

Key Exclusion Criteria:

1. Receipt of 2 or more prior systemic treatments for advanced/metastatic unresectableESCC

2. History of gastrointestinal perforation and /or fistula or aorto-esophageal fistulawithin 6 months prior to randomization

3. Tumor invasion into organs located adjacent to the esophageal disease site (eg,aorta or respiratory tract) at an increased risk of fistula in the study treatmentassessed by investigator

4. Uncontrollable pleural effusion, pericardial effusion, or ascites requiring frequentdrainage

5. Received prior therapies targeting programmed death 1 (PD-1) or programmed deathligand 1 (PD-L1)

6. Prior malignancy active within the previous 2 years (exceptions include the tumorunder investigation in this trial, and locally recurring cancers that have undergonecurative treatment, such as resected basal or squamous cell skin cancer, superficialbladder cancer or carcinoma in situ of the prostate, cervix or breast)

7. Active brain or leptomeningeal metastasis.

8. Has active autoimmune disease or history of autoimmune diseases at high risk forrelapse

9. Known history of, or any evidence of interstitial lung disease, non-infectiouspneumonitis, pulmonary fibrosis diagnosed based on imaging or clinical findings, oruncontrolled systemic diseases, including diabetes, hypertension, acute lungdiseases, etc

10. Known history of Human Immunodeficiency Virus (HIV)

11. Has cardiovascular risk factors

12. Pregnant or breastfeeding woman.

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