A phase II study to assess the efficacy and safety of Surufatinib combined with Sintilimab as a second-line treatment in patients with advanced MSS-Type CRC.

Inclusion Criteria:

1. For inclusion in study, patient must provide a written informed consent.
2. Male or female, age18-75 years.
3. Pathologically confirmed unresectable locally advanced or advanced MSS-Type metastatic colorectal adenocarcinoma .
4. The patient had previously failed standard first-line systemic chemotherapy,Prior adjuvant and neo-adjuvant therapy is permitted (chemotherapy, radiotherapy, investigational agents) if 6 months or more have passed since completion of therapy.
5. Eastern Cooperative Oncology Group (ECOG) performance status: 0 or 1.
6. Life expectancy > 12 weeks.
7. Have measurable disease based on RECIST 1.1.

Exclusion Criteria:

1. Any therapy with anti-PD-1, or anti-PD-L1/l2 antibodies or anti-cytotoxic T lymphocyte associated antigen-4 (CTLA-4) antibody (or any other antibody acting on T cell costimulatory or checkpoint pathway) or fruquintinib treatment in previous.
2. Prior receipt of Surufatinib.
3. History of any active autoimmune disease or autoimmune disease, including but not limited to interstitial pneumonia, uveitis, inflammatory bowel disease, hepatitis, pituitary inflammation, vasculitis, systemic lupus erythematosus, etc. (except patients with hypothyroidism that can be controlled only by hormone replacement therapy and patients with type I diabetes who only need insulin replacement therapy).
4. History of gastrointestinal perforation and/or fistula, ileus, inflammatory bowel disease, or extensive enterotomy (partial colectomy or extensive enterotomy with chronic diarrhea), Crohn's disease, ulcerative colitis, or chronic diarrhea within 6 months prior to first dosing.
5. Any life-threatening bleeding event or grade 3 or 4 bleeding requiring blood transfusion, endoscopy, or surgery with 3 months prior to dosing.