A Phase I Study of SY-9453 in Patients With Advanced Solid Tumors

Inclusion Criteria: Patients must meet all of the following criteria to be eligible for this study: 1. Subjects voluntarily participated in this study and signed the written informed consent (ICF); 2. Age ≥ 18 years at the time of signing the Informed Consent Form (ICF); 3. Histologically or cytologically confirmed locally advanced solid tumor and disease progression or intolerance after adequate standard treatment, or lack of standard treatment options. For subjects participating in the dose escalation phase (only for dose groups of 30 mg and above) and the dose expansion phase: be able to provide a previous test report confirmed by NGS or IHC to be homozygous deletion of the MTAP gene approved by the investigator, or agree to provide sufficient archived or baseline tumor tissue samples, confirmed to be homozygous deletion of the MTAP gene by central laboratory testing. 4.At least one measurable extracranial lesion as defined by Response Evaluation Criteria in Solid Tumors (RECIST) v 1.1 criteria or mRECIST V1.1（Mesothelioma subjects only）(subjects participating in accelerated titration phase are not required to meet this requirement). 5.Expected survival of \>3 months. 6.Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1. 7.Organ function levels must meet the following requirements: 1. No blood products, hematopoietic growth factors (e.g., G-CSF, thrombopoietin, erythropoietin, platelet transfusion, whole blood transfusion, red blood cell transfusion), or other drugs that correct abnormal blood counts for at 14 days before first dosing and the following blood counts: ANC ≥ 1.5 × 10\^9/L, PLT count ≥ 100 × 10\^9/L, Hb ≥ 90 g/L. 2. Renal function: Creatinine clearance (Ccr) ≥ 60 mL/min (calculated using the Cockcroft and Gault formula). 3. Liver function: TBIL ≤ 1.5 × upper limit of normal (ULN), and AST and ALT ≤ 2.5 × ULN; in the presence of liver metastases, AST and ALT ≤ 5.0 × ULN, and serum albumin ≥ 30 g/L. 4. Coagulation function: Activated Partial Thromboplastin Time (APTT) ≤ 1.5 × ULN, and International normalized ratio (INR) or prothrombin time (PT) ≤ 1.5 × ULN (except for patients receiving anticoagulant therapy). 8.Female patients with reproductive potential must have a negative serum pregnancy test within 7 days prior to the first dose, male and female patients of childbearing potential must be willing to completely abstain or agree to use an appropriate method of contraception during the entire study duration and for at least 3 months after the last dose of study medication. Exclusion Criteria: 1\. Patients previously treated with a MAT2A inhibitor or PRMT5 inhibitor. 2. History of allergy to any component or excipient of SY-9453 capsules. 3. Received the following treatments prior to the first dose: 1. Small-molecule targeted drugs within 2 weeks(or 5 half-lives, whichever is shorter). 2. Hormonal anti-tumor therapy within 2 weeks or as judged by the investigator. 3. Chinese herbal medicine or preparations with indications for anti-tumor therapy or tumor adjuvant therapy within 2 weeks or as judged by the investigator. 4. Radiotherapy within 4 weeks (with 2 weeks if the radiotherapy was palliative stereotactic radiotherapy that did not involve the lungs, abdomen and pelvis) 5. Chemotherapy: fluorouracil, leucovorin, and/or weekly paclitaxel with 2 weeks; nitrosourea or mitomycin C with 6 weeks; other chemotherapy with 3 weeks. 6. Other investigational drugs with 4 weeks. 7. Biotherapy within 4 weeks(or 5 half-lives, whichever is longer) 8. Immunotherapy within 4 weeks. 9. Major surgery within 4 weeks (excluding central venous catheter insertion, bone marrow biopsy and gastric tube insertion). 10. Radioactive Particle Therapy within 3 months. 11. Radionuclide therapy within 3 months. 12. Autotransplantation (including CAR-T therapy and other similar treatments) within 3 months. 4.Adverse events from prior anti-cancer therapies have not recovered to Grade ≤1 as defined by the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) v5.0 (except for toxicities assessed by the investigator as posing no safety risk, such as alopecia and Grade 2 peripheral neuropathy). 5.Other malignancies within 3 years before screening, with the following exceptions: cured cervical carcinoma in situ, squamous cell carcinoma of the skin, and cured basal cell carcinoma(except for the subjects participating in accelerated titration phase). 6.Dysphagia, or presence of a gastrointestinal disorder or other malabsorption condition that affects drug absorption, such as intestinal obstruction, Crohn's disease, ulcerative colitis, severe peptic ulcer, gastrointestinal perforation, or acute gastrointestinal bleeding. 7\. Presence of active central nervous system (CNS) disease (if the clinical performance is stable assessed by the investigator at least 4 weeks before the first dose of SY-9453, and steroid treatment has been discontinued for ≥14 days, the patients can be included. 8.Hepatitis B during screening (positive results for hepatitis B surface antigen \[HBsAg\] and/or hepatitis B core antibody \[HBcAb\] with HBV-DNA ≥1000 IU/mL; patients whose HBV-DNA levels drop to below 1000 IU/mL after regular antiviral treatment can be included), or active hepatitis C (HCV RNA \> central detection upper limit of normal \[ULN\]), active syphilis (positive for both Treponema pallidum-specific and non-specific antibodies); history of tuberculosis (evidence of active tuberculosis infection within 1 year), Human immunodeficiency virus (HIV) positive during screening, or known history of other immunodeficiency diseases. 9.Presence of other underlying medical conditions as assessed by the investigator may put the subject at risk or affect the assessment of the toxicity of SY-9453 or AEs. 10\. History of neurological or mental disorders, such as dementia. 11. Presence of the following clinically significant comorbidities, including but not limited to: