This is an open label, single-arm, multi-center, phase II study of SHR-1701 in patients with recurrent/metastatic SCCHN

Inclusion Criteria:

1. Histologically confirmed Recurrent/Metastatic SCCHN,not include NPC
2. Subjects failure after 1 lines of platinum based chemotherapy or failure from anti-PD-1/PD-L1 antibody therapy.
3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 at trial entry.
4. Disease must be measurable with at least 1 uni dimensional measurable lesion by Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.
5. Adequate hematological, hepatic and renal function as defined in the protocol Other protocol-defined inclusion criteria could apply.

Exclusion Criteria:

1. Prior therapy with an anti-PD1, anti-PD-L1, anti-CTLA-4 or a TGFb inhibitor.
2. Anticancer treatment within 28 days before the first dose of study drug.
3. Major surgery within 28 days before start of trial treatment.
4. Systemic therapy with immunosuppressive agents within 7 days prior to the first dose of study drug; or use any investigational drug within 28 days before the start of trial treatment.
5. With any active autoimmune disease or history of autoimmune disease.
6. History of immunodeficiency including seropositive for human immunodeficiency virus (HIV), or other acquired or congenital immunedeficient disease, or any active systemic viral infection requiring therapy.