This study will evaluate the safety, tolerability, pharmacokinetics and treatment effect of CS1001 in combination with Donafenib in patients with advanced solid tumors.

This trail uses an open, multi-center study design, Contains two parts: a dose escalation part and a dose expansion part.

Inclusion Criteria:

• Fully understand this study and voluntarily sign ICF;
• 18 to 75 years old (including 18 and 75 years old), male or female;
• Subjects with advanced solid tumors, including:

Phase I study:

subjects with advanced solid tumors confirmed by histology or cytology that are not suitable for surgical resection, or have failed or tolerated standard treatment, or have no standard treatment. Including but not limited to Cholangiocarcinoma , head and neck squamous cell carcinoma (HNSCC) and endometrial cancer.

Exclusion Criteria:

• Any history of active autoimmune diseases or autoimmune diseases; patients with vitiligo or asthma that has been completely relieved in childhood, and patients who do not need any intervention after adulthood can be included;
• Participants with any condition that impairs their ability to take oral medication, such as lack of physical integrity of the upper gastrointestinal tract or malabsorption syndrome.
• Patients with uncontrolled pleural effusion, pericardial effusion, or ascites requiring repeated drainage and need to retain a catheter;
• Human immunodeficiency virus (HIV) antibody positive;
• Patients who are simultaneously infected with hepatitis B virus and hepatitis C virus;
• Lactating women. If they are willing to stop breastfeeding, they can also be included in this study.