This is a first-in-human (FIH), open-label, and multi-center Phase I study designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of CS5007 as monotherapy in participants with advanced solid tumors. The study is comprised of a Phase Ia dose escalation and Phase Ib dose expansion.

Inclusion Criteria:

• Evidence of a personally signed and dated informed consent document.
• Willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures.
• Being ≥ 18 years of age on the day of signing informed consent.
• Pathologically or cytologically confirmed, unresectable advanced solid tumors.
• Participants must have at least one measurable lesion according to RECIST Version1.1.
• Eastern Cooperative Oncology Group (ECOG) Performance Score of 0 or 1.
• Adequate organ function.
• Life expectancy ≥ 3 months.
• Fertile men and women of childbearing potential must agree to use an effective method of birth control from providing signed consent and for 180 days after the last study drug administration

Exclusion Criteria:

• Has disease that is suitable for local treatment administered with curative intent.
• Has a history of a second malignancy active within the previous 3 years except for locally curable cancers that have been apparently cured.
• Known primary central nervous system (CNS) tumor or solid tumor CNS metastasis that is symptomatic, untreated, or requires therapy.
• Has life-threatening bleeding event or severe bleeding within 3 months prior to first dose.
• Has uncontrolled pleural effusion, pericardial effusion, or ascites.
• Has immune deficient disease or received systemic immunosuppressive treatment.
• Has intestinal obstruction,or history of inflammatory bowel disease,or chronic diarrhea.
• Has history of (non-infectious) interstitial lung disease/pneumonitis that required steroids.
• Has active infections requiring systemic therapy.
• Has significant cardiovascular disease or cerebrovascular accident within specified timeframes prior to first dose.
• Insufficient washout from prior anti-tumor therapy.
• Received live vaccine within 28 days prior to first dose.
• History of allogeneic organ or hematopoietic stem cell transplantation.
• History of hypersensitivity to excipients of study drug or any monoclonal antibody.
• Any toxic effects of prior therapy unresolved to Grade ≤1.
• Active alcohol or drug abuse.
• Pregnant or breastfeeding women.
• Other acute or chronic medical or psychiatric conditions that may increase risk or interfere with study results, in the investigator's judgment.