A Study to Evaluate YF087 in Subjects With MSI-H or dMMR Advanced Solid Tumors

Inclusion Criteria: * Subjects with locally advanced (unresectable) or metastatic solid tumors; * dMMR/MSI-H status demonstrated in tumor tissue, blood, or other samples containing cancer cells or DNA; * Subjects must have experienced disease progression after the most recent therapy for advanced disease (prior therapy must include at least one PD-1/PD-L1 inhibitor treatment). * Presence of at least 1 measurable lesion that can be measured by CT or MRI based on RECIST V1.1 criteria; * ECOG≤1 Exclusion Criteria: * Prior treatment with a WRN inhibitor such as HRO760, RO7589831, GSK4418959 and NDI-219216; * Prior to the first dose of study intervention, receipt of any anticancer treatment (including chemotherapy, targeted therapy, immunotherapy, etc.) or any other investigational medicinal product within 14 days or 3 half-lives (whichever is shorter); * Subjects with unstable or symptomatic or progressive central nervous system (CNS) metastases and/or leptomeningeal carcinomatosis and/or brainstem metastases and/or spinal cord compression; * Subjects with clinically significant cardiovascular and cerebrovascular disease * Subjects with concomitant medical conditions that the investigator believes may increase the risk of toxicity, such as serious cardiovascular, respiratory or neurological diseases; * Use of, or planned use of, any of the following medications that has not been discontinued for at least 14 days or 5 half-lives (whichever is shorter) before the first study drug administration: 1. Strong CYP3A4 inducers or inhibitors; 2. Drugs known to prolong the QT interval. * Pregnant or lactating females;