Surufatinib Combined with Envolizumab As Second-line Treatment for Recurrent/Metastatic HNSCC

envolizumab: 300 mg subcutaneously every 3 weeks (Q3W); Surufatinib : 200 mg orally within 1 hour after breakfast, once daily continuously every 3 weeks as a treatment cycle until intolerable toxicity or disease progression. If any ≥ Grade 2 treatment-related adverse event occurs during treatment, the dose may be adjusted to 100 mg according to the investigator 's clinical assessment.