A Phase lb/lI Clinical Study in Advanced or Metastatic Esophageal Squamous Cell Carcinoma

Inclusion Criteria: 1. age:18-75 years old, Male or female patients 2. Histologically or cytologically confirmed esophageal squamous cell carcinoma (including the gastroesophageal junction), (Adenosquamous carcinoma with squamous cell carcinoma components-based is allowed to be included) 3. Irretrievably resected, local advanced, relapsed or metastatic esophageal squamous cell carcinoma 4. Previously received platinum-based systemic anti-tumor first-line therapy; Or received Neoadjuvant, adjuvant therapy, or radical chemoradiotherapy for ESCC, but disease recurrence or progression within 6 months after completion of treatment; no restrictions on prior immunotherapy treatment choice. 5. Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 to 1 6. At least one measurable lesion (RECIST1.1) 7. Life expectancy of more than 3 months; 8. Women of childbearing age were required to have had a negative pregnancy test (serum or urine) within 14 days before enrollment and to voluntarily use an appropriate method of contraception during the observation period and for 8 weeks after the last dose of the study drug.For men, either surgical sterilization or consent to use an appropriate method of contraception during the observation period and for 8 weeks after the last dose of the study drug was given 9. Have fully understood and voluntarily sign the ICF for this study; 10. Willingness and ability to comply with scheduled visits, treatment plans, laboratory tests, and other study procedure; 11. Adequate hepatic, renal, heart, and hematologic functions Exclusion Criteria: 1. Have had other malignancies within the past 5 years, except for curatively treated radical skin basal cell or squamous cell carcinoma, Or cervical carcinoma in situ; 2. Have received major surgical procedures (such as craniotomy, thoracotomy, or laparotomy) within 4 weeks before enrollment or are excepted to uddergo major surgery during the study treatment; received laparoscopic exploration within 2 weeks before enrollment; received central venous catheterization within 7 days prior to enrollment 3. Have received chemotherapy, targeted therapy, traditional Chinese herbal medicine with anti-tumor indications or immunomodulatory drugs (including thymosin, interferon, interleukins, etc.) within the first 4 weeks prior to enrollment, or are still within 5 half-lives of such medications 4. Have symptomatic central nervous system metastases (with stable brain metastases confirmed by imageology for more than 3 months were eligible) 5. Severe infection ((≥CTCAE grade 2 infection) occurred within 4 weeks before the first dose of study drug, such as severe pneumonia requiring hospitalization, bacteremia, and infectious complications;Baseline chest imaging suggested active pulmonary inflammation with clinically relevant symptoms or signs;the presence of signs and symptoms of infection within 2 weeks before the first dose of the study drug ,or the need for treatment with oral or intravenous antibiotics was excluded if prophylactic antibiotics were used; 6. Previous and current presence of interstitial pneumonia, pneumoconiosis, drug-related pneumonia, and severely impaired pulmonary function may interfere with the detection and management of suspected drug-related pulmonary toxicity in subjects;Subjects with radiation pneumonitis within 6 months 7. Had active pulmonary tuberculosis by medical history or CT examination, or who had a history of active pulmonary tuberculosis within 1 year before enrollment ,or who had a history of active pulmonary tuberculosis more than 1 year before enrollment but had not received regular treatment 8. Congenital or acquired immune deficiency, such as human immunodeficiency virus (HIV) infection, active hepatitis B (HBV DNA ≥ 500 IU/ml), hepatitis C (hepatitis C antibody positive, and HCV-RNA above the detection limit of the assay) or co-infection with hepatitis B and C; 9. Known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation 10. With thrombotic diseases or receiving anticoagulant drugs; 11. Patients at risk of gastrointestinal hemorrhage or obstruction; 12. Unable to swallow the experimental drug; 13. Patients who have previously experienced immune-related myocarditis, pneumonitis, colitis, hepatitis, nephritis, etc.were judged to be at greater risk for immunotherapy retreatment by the investigator; 14. Patients with complications who require long-term use of immunosuppressive drugs or those who need systemic or local administration of corticosteroids with immunosuppressive effects 15. Patients considered unsuitable for inclusion in this study by the investigator