KN046 in Patients With Recurrent or Metastatic Esophageal Squamous Cell Carcinoma

Inclusion Criteria:

* Signed inform consent form(ICF)
* Age ≥ 18 years and ≤ 75 years, male or female
* Histologically or cytologically documented recurrent or metastatic esophageal squamous cell carcinoma, with indications of radiotherapy and without prior systemic treatment
* At least one measurable lesion according to Response Evaluation Criteria In Solid Tumors（RECISIT） v 1.1
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
* Adequate organ function
* Female patients and males with partners of childbearing potential should be using highly effective contraceptive measures (failure rate of less than 1% per year). Contraception should be continued for a period of 24 weeks after dosing has been completed.
* Ability to comply with treatment, procedures and pharmacokinetics (PK) sample collection and the required study follow-up procedures

Exclusion Criteria:

* Known brain metastasis or another Central Nervous System (CNS) metastasis that is either symptomatic or untreated.
* Patients who are participating or have participated in a study of an investigational drug within 4 weeks prior to the first dose of trial treatment.
* Patients who have received immune checkpoint proteins/antibody/medicine for treatment.
* Patients who have interstitial lung disease, or a history of pneumonitis that required oral or intravenous glucocorticoids to assist with management.
* Subjects with active autoimmune diseases or history of autoimmune diseases should be excluded
* Active Hepatitis B Virus (HBV) or Hepatitis C Virus (HCV) infection.
* Known HIV infection or known history of acquired immune deficient syndrome (AIDS)
* Any unresolved the Common Terminology Criteria for Adverse Events (CTCAE) Grade ≥ 2 toxicities from prior anti-cancer therapy except for vitiligo, alopecia
* Patients who have serious hypersensitive reaction to monoclonal antibodies and have history of uncontrolled allergic asthma