This is a non-randomized, phase II, open label study of apatinib mesylate tablets plus tegafur gimeracil oteracil potassium capsules in recurrent/metastatic squamous cell carcinoma of head and neck. The primary purpose of this study is to evaluate the efficacy of apatinib mesylate tablets plus tegafur gimeracil oteracil potassium capsules in recurrent/metastatic squamous cell carcinoma of head and neck

Inclusion Criteria:

1. Histologically / cytologically confirmed diagnosis of recurrent or metastatic squamous cell carcinoma of head and neck origin not amenable to curative intent therapy; both human papillomavirus (HPV)(+) and HPV(-) tumors are eligible; tumors (squamous histology) of unknown primary that are clearly related to the head and neck area are eligible

2. Presence of measurable lesions (RECIST V1.1)

3. Eastern Cooperative Oncology Group (ECOG) performance status =< 2

4. Absolute neutrophil count (ANC) >= 1.5 x 10^9/L

   • Platelets >= 100 x 10^9/L
   • Hemoglobin (Hb) > 9 g/dL
   • Total calcium (corrected for serum albumin) within normal limits
   • Magnesium >= the lower limit of normal for the institution
   • Potassium within normal limits for the institution
   • Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) within 1.5 x normal range (or =< 3.0 x upper limit of normal [ULN] if liver metastases are present)
   • Serum bilirubin within normal range (or =< 1.5 x ULN if liver metastases are present; or total bilirubin =< 3.0 x ULN with direct bilirubin within normal range in patients with well documented Gilbert syndrome)
   • Serum creatinine =< 1.5 x ULN or 24-hour clearance >= 50 mL/min
   • Serum amylase =< ULN
   • Serum lipase =< ULN
   • Fasting plasma glucose =< 120 mg/dL (6.7 mmol/L)

5. Negative serum pregnancy test within 72 hours before starting study treatment in women with childbearing potential

6. Signed informed consent

Exclusion Criteria:

1. Patients with poor-controlled arterial hypertension (systolic pressure ≥ 140 mmHg and/or diastolic pressure ≥ 90 mm Hg) despite standard medical management;
2. Suffered from grade II or above myocardial ischemia or myocardial infarction, uncontrolled arrhythmias (including QT interval male ≥ 450 ms, female ≥ 470 ms). Grade III-IV cardiac insufficiency according to New York Heart Association (NYHA) criteria or echocardiography check: left ventricular ejection fraction (LVEF)<50%;
3. Patients who have had prior allergic reaction to Apatinib;
4. The subject has had another active malignancy within the past five years except for cervical cancer in site, in situ carcinoma of the bladder or non-melanoma carcinoma of the skin;
5. Clinically significant and uncontrolled major medical conditions including but not limited to: active uncontrolled infection, symptomatic congestive heart failure, Unstable angina pectoris or cardiac arrhythmia, psychiatric illness/ social situation that would limit compliance with study requirements; any medical condition, which in the opinion of the study investigator places the subject at an unacceptably high risk for toxicities;
6. Patients undergoing therapy with other investigational agents.
7. Women who are pregnant or breastfeeding;
8. Patients with any other concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for participation in the study.