Surufatinib in Combination With Tislelizumab in Subjects With Advanced Solid Tumors

Inclusion Criteria:

1. Willing and able to provide informed consent
2. ≥18 years of age
3. Part 1-have evaluable lesions (according to Response Evaluation Criteria in Solid Tumors version 1.1 \[RECIST v1.1\])
4. Part 2-have measurable lesions (according to RECIST v1.1)
5. Have a performance status of 0 or 1 on the ECOG scale
6. For female subjects of childbearing potential and male patients with partners of childbearing potential, agreement to use a highly effective form(s) of contraception

   Dose Escalation:
7. Histologically or cytologically documented, locally advanced or metastatic solid malignancy of any type,.

   Dose Expansion:
8. Histologically or cytologically documented, locally advanced or metastatic:

Cohort A: adenocarcinoma of the colon or rectum that is microsatellite stable. Subjects must have progressed on, or had intolerable toxicity to, at least 3 prior regimens of standard chemotherapy.

Cohort B: progressive, low or intermediate grade (grade 1 or grade 2) NETs of thoracic or GEP origins. Subjects must have radiological documentation of progression of disease in the last 6 months and must have progressed on at least one line of standard therapy for metastatic disease.

Cohort C: SCLC that has progressed on standard first line chemotherapy treatment.

Cohort D: adenocarcinoma of the stomach or gastroesophageal junction and have progressed on at least 2 prior lines of therapy. Tumor stain for PD-L1 by Combined Positive Score (CPS) ≥5%.

Cohort E: ASPS or UPS. Subjects must have radiological documentation of disease progression in the last 3 months and have progressed on at least one line of standard therapy or refused standard frontline cytotoxic chemotherapy.

Cohort F: Anaplastic thyroid cancer that is considered not curable by resection. Patients with a BRAFV600E mutation must have previously been treated with 1 line of systemic therapy with a BRAF-targeted therapy.

Exclusion Criteria:

1. Adverse events (AEs) due to previous anti-tumor therapy has not recovered to Common Terminology Criteria for Adverse Event (CTCAE) ≤Grade 1;
2. Part 2 subjects with CRC , NETs and STS any previous treatment with anti-PD-1, anti PD-L1/L2 antibodies, anti-cytotoxic T lymphocyte associated antigen-4 (CTLA-4) antibody, or any other antibody acting on T cell costimulatory or checkpoint pathway;
3. Previous treatment with surufatinib;
4. Uncontrollable hypertension;
5. History or presence of a serious hemorrhage (\>30 ml within 3 months), hemoptysis (\>5 ml blood within 4 weeks) or life threatening thromboembolic event within 6 months;
6. Clinically significant cardiovascular disease;
7. Any clinically significant active infection, including, but not limited to, known human immunodeficiency virus (HIV) infection;
8. Brain metastases and/or leptomeningeal disease and/or spinal cord compression untreated with surgery and/or radiotherapy, and without clinical imaging evidence of SD for 14 days or longer; subjects requiring steroids within 4 weeks prior to start of study treatment will be excluded;
9. Active autoimmune diseases or history of autoimmune diseases that may relapse with the following exceptions:

   1. Controlled Type 1 diabetes
   2. Hypothyroidism (provided it is managed with hormone-replacement therapy only)
   3. Controlled celiac disease
   4. Skin diseases not requiring systemic treatment (eg, vitiligo, psoriasis, or alopecia)
   5. Any other disease that is not expected to recur in the absence of external triggering factors.
10. Arterial thrombosis or thromboembolic events (including stroke and/or transient ischemic attack) within 12 months prior to first dosing;
11. History of deep venous thrombosis within 6 months;
12. Female patients who are pregnant or breastfeeding;
13. Any condition by which investigators judge patients not suitable to participate in this study.