A Phase 1, Multicenter, Open-Label, First-in-Human Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of YL217 in Patients With Advanced Solid Tumors

Inclusion Criteria: * Informed of the study before the start of the study and voluntarily sign their name and date in the ICF * Able and willing to comply with protocol visits and procedures * Age≥ 18 years * ECOG PS of 0 or 1 * Tumor types as below: For Part 1 and Part 2: Pathologically confirmed diagnosis of an advanced solid tumor. For Part 3 (Histologically or cytologically confirmed diagnosis+ locally advanced unresectable or metastatic disease) * Adequate organ and bone marrow function. * Have at least 1 extracranial measurable tumor lesion. * Adequate archival formalin-fixed paraffin embedded （FFPE） tissue from prior biopsy. Exclusion Criteria: * Prior treatment with an agent targeting CDH17 * Prior discontinuation of a topoisomerase I inhibitor due to treatment-related toxicities. * Have received an ADC consisting of a topoisomerase I inhibitor. * Concurrent enrollment in another clinical study, unless it is an observational clinical study. * Inadequate washout period for prior anticancer treatment before the first dose of study drug * Undergone major surgery within 4 weeks before the first dose of study drug or expect major surgery during the study. * Received long term systemic steroids or other immunosuppressive therapy within 2 weeks before the first dose of study drug. * Received any live vaccine within 4 weeks before the first dose of study drug or intend to receive a live vaccine during the study. * Diagnosis or evidence of spinal cord compression or leptomeningeal carcinomatosis. * Uncontrolled or clinically significant cardiovascular and cerebrovascular diseases. * A history of non-infectious interstitial lung disease (ILD)/pneumonitis that requires steroids, current active ILD/pneumonitis. * Have clinically severe pulmonary compromise resulting from intercurrent pulmonary illnesses. * Uncontrolled third-space fluid that requires repeated drainage. * Digestive system disease that may cause bleeding, perforation, jaundice, gastrointestinal obstruction. * An active tuberculosis based on medical history. * Known human immunodeficiency virus (HIV) infection. * Active hepatitis C infection.