Toripalimab and Gemcitabine in Recurrent or Metastatic Nasopharyngeal Carcinoma.

Inclusion Criteria:

1. Male or female; 18-70 years of age.
2. Subjects diagnosed with pathological confirmed metastatic nasopharyngeal carcinoma, or subjects with recurrent NPC that is unfit for local treatment.
3. did't receive any systemic chemotherapy for recurrent and metastatic lesions.
4. Intolerance to or rejection of platinum-based chemotherapy
5. ECOG performance status of 0 or 1.
6. Life expectancy more than 12 weeks.
7. Subjects enrolled must have measurable lesion(s) according to response evaluation criteria in solid (RECIST) v1.1.
8. Adequate organ function assessed by laboratory parameters during the screening period
9. Female subjects agree not to be pregnant or lactating from beginning of the study screening through at least 3 months after receiving the last dose of study treatment. Both men and women of reproductive potential must be willing and able to employ a highly effective method of birth control/contraception to prevent pregnancy. A highly effective method of contraception is defined as one that results in a low failure rate, that is, less than 1% per year when used consistently and correctly
10. Able to understand and sign an informed consent form (ICF).

Exclusion Criteria:

1. Subjects with any active autoimmune disease or history of autoimmune disease, or history of syndrome that requires systemic steroids or immunosuppressive medications, including but not limited to the following: rheumatoid arthritis, pneumonitis, colitis (inflammatory bowel disease), hepatitis, hypophysitis, nephritis, hyperthyroidism, and hypothyroidism, except for subjects with vitiligo or resolved childhood asthma/atopy. Subjects with the following conditions will not be excluded from this study: asthma that requires intermittent use of bronchodilators, hypothyroidism stable on hormone replacement, vitiligo, Graves' disease, or Hashimoto's disease. Additional exceptions may be made with medical monitor approval;
2. Known history of hypersensitivity to any components of the Toripalimab formulation;
3. Concurrent medical condition requiring the use of immunosuppressive medications, or immunosuppressive doses of systemic or absorbable topical corticosteroids. Doses 10 mg/day prednisone or equivalent are prohibited within 2 weeks before study drug administration. Note: corticosteroids used for the purpose of IV contrast allergy prophylaxis are allowed;
4. Active central nervous system (CNS) metastases (indicated by clinical symptoms, cerebral edema, steroid requirement, or progressive disease);
5. Uncontrolled clinically significant medical condition, including but not limited to the following:

   1. congestive heart failure (New York Health Authority Class \> 2),
   2. unstable angina,
   3. myocardial infarction within the past 12 months,
   4. clinically significant supraventricular arrhythmia or ventricular arrhythmia requiring treatment or intervention;
6. Active infection or an unexplained fever; 38.5°C during screening visits or on the first scheduled day of dosing (at the discretion of the investigator, subjects with tumor fever may be enrolled);
7. History of immunodeficiency including seropositivity for human immunodeficiency virus (HIV), or other acquired or congenital immune-deficient disease;
8. Any other medical (eg, pulmonary, metabolic, congenital, endocrinal, or CNS disease), psychiatric, or social condition deemed by the investigator to be likely to interfere with a subject's rights, safety, welfare, or ability to sign informed consent, cooperate, and participate in the study or would interfere with the interpretation of the results; Evidence of hepatitis B virus (HBV) or hepatitis C virus (HCV) infection or risk of reactivation based on institutional guidelines and tests. Testing may include the following: HBV DNA, HCV RNA, hepatitis B surface antigen, or anti-Hepatitis B core antibody.