A Clinical Trial Comparing HLX10 With Placebo Combined With Chemotherapy (Cisplatin + 5-fu) in the First-line Treatment of Locally Advanced/Metastatic Esophageal Squamous Cell Carcinoma (ESCC)

Inclusion Criteria: * Subjects who meet all of the following criteria are allowed to be enrolled into this study: * Volunteer to participate in this clinical study; completely understand and know this study as well as sign the informed consent form (ICF); be willing to follow and be able to complete all study procedures; * Age ≥ 18 years and ≤ 75 years when ICF is signed; * Never received systemic anti-tumor drug therapy before.Exception: for patients who have received neoadjuvant/adjuvant treatment, the time from the last treatment to recurrence or progression can be screened for more than 6 months;For patients who have received radical concurrent chemoradiotherapy or radiotherapy for esophageal cancer, the time from the last chemotherapy/radiotherapy to the recurrence or progression time is more than 12 months. * According to the curative effect evaluation criteria in solid tumors (RECIST) v1.1, assessed by the center image with at least one measurable lesions (such as esophageal cavity structure not as measurable lesions), measurable lesions should be not received radiotherapy, etc (lesions located in the usual radiation area, if confirm progress, can also be selected as the target lesion); * PD-L1 positive subjects (CPS 1%).The subject must provide tumor tissue for pd-l1 expression level determination; * Within 7 days before the first use of the study drug, ECOG: 0 \~ 1; * Expected survival 12 weeks; * The functions of the vital organs meet the following requirements (no blood transfusion, cytokine growth factor, or platelet raising drugs are allowed within 14 days before the first use of the study drugs); H. Absolute neutrophil count (ANC) ≥1.5 109/L I. platelet≥ 100 109/L; J. Hemoglobin≥ 9g/dL; K. Serum albumin≥ 3.0g/dL; L. Total bilirubin≤ 1.5 ULN, ALT, AST and/or ALP≤ 2.5 ULN;ALT and/or AST≤ 5 ULN in the presence of liver metastasis;If there is liver metastasis or bone metastasis ALP≤ 5 ULN; M. Serum creatinine ≤1.5 ULN or creatinine clearance \> 60 mL/min (Cockcroft-Gault formula); N. APTT, INR and PT ≤1.5 ULN; * For fertile female subjects, the serum pregnancy test must be negative within 7 days before the first dose.With fertile women subjects, and the partner for childbearing age women of male subjects, needs during the therapy, and after the last use HLX10 / placebo at least 3 months and the last time to use at least 6 months after chemotherapy using an approved by the medical contraception (such as intrauterine device, the pill or condoms); * Subjects voluntarily participated in this study and signed the informed consent, with good compliance and follow-up. Exclusion Criteria: * Subjects who meet any of the following criteria are not allowed to be enrolled in this study: * 1\. BMI \< 17.5kg /m2; * 2\. A history of gastrointestinal perforation and/or fistula within 6 months prior to the first administration; * 3\. Obvious invasion of tumor into adjacent organs (aorta or trachea) of esophageal lesions leads to high risk of bleeding or fistula;3. Subjects after endotracheal stent implantation; * 4\. Uncontrollable pleural effusion, pericardial effusion or ascites requiring repeated drainage; * 5\. Previous allergies to monoclonal antibody, HLX10, 5-fu, cisplatin and other platinum drugs; * 6.Have received any of the following treatments: A. Previous treatment with anti-pd-1 or anti-pd-L1 antibodies; B. Have received any research drugs within 4 weeks before the first use of the study drugs; C. Be enrolled in another clinical study at the same time, unless it is an observational (non-interventional) clinical study or a follow-up interventional clinical study; D. Receive the final anticancer treatment within 4 weeks before the first use of the study drug;Palliative radiotherapy for bone metastases was allowed and was completed 2 weeks before the first dose.Radiotherapy covering more than 30% of the bone marrow area is not allowed within 28 days before the first dose. E. Subjects who require systemic treatment with corticosteroids (\> 10 mg/ day prednisone therapeutic dose) or other immunosuppressive agents within 14 days prior to the first use of the study drug;In the absence of active autoimmune disease, inhalation or topical use of steroids is permitted, and the therapeutic dose of prednisone 10mg/ day is allowed. F. Those who have received the anti-tumor vaccine or the live vaccine within 4 weeks before the first dose of the study drug; G. Have undergone major surgery within 28 days prior to the first use of the study drug. Major surgery in this study is defined as requiring at least 3 weeks of postoperative recovery time before being able to receive the surgery treated in this study.Tumor puncture or lymph node biopsy were allowed.