TR115 in ARID1A-Mutated Advanced Solid Tumors

Inclusion Criteria: * Able to understand and provide written informed consent. * Age 18 to 70 years, inclusive. * Histologically or cytologically confirmed advanced solid tumor with ARID1A mutation. * Cohort 1: Platinum-resistant ovarian/fallopian tube/peritoneal clear cell carcinoma with disease progression after ≥1 prior platinum-based regimen. Cohort 2: Endometrial cancer with disease progression after ≥1 prior platinum-based regimen and prior immunotherapy failure or intolerance. Cohort 3: Other advanced solid tumors (including gastric cancer, urothelial carcinoma) with disease progression after ≥1 prior standard systemic therapy. * ECOG performance status 0-1. * Life expectancy ≥3 months. * At least one measurable lesion per RECIST v1.1. * Adequate organ function: ANC ≥1.5×10⁹/L, PLT ≥100×10⁹/L, Hb ≥100 g/L (no growth factor or transfusion support within 14 days prior to first dose), TBIL ≤1.5×ULN, ALT/AST ≤2.5×ULN (≤5×ULN if liver metastasis), CrCl ≥50 mL/min, LVEF ≥50%, QTcF \<450 ms (male) or \<470 ms (female). * Willing to provide archival or fresh tumor tissue for biomarker analysis. * Male and female participants of childbearing potential must agree to use medically approved contraception during the study and for 6 months after the last dose. Exclusion Criteria: * Prior treatment with EZH2 or EZH1/2 inhibitors resulting in disease progression (intolerance permitted). * Third-space fluid accumulation not controllable by drainage or other means. * Systemic corticosteroid therapy (\>10 mg/day prednisone or equivalent) within 14 days prior to first dose, except for inhaled or topical use. * Inability to swallow oral medication or conditions significantly affecting drug absorption. * Known central nervous system (CNS) involvement. * Tumor invasion or encasement of major vessels. * Active infection requiring systemic therapy. * Active hepatitis B or C requiring treatment, or HIV infection. * Active autoimmune disease requiring systemic immunosuppressive therapy. * Significant cardiovascular disease (e.g., myocardial infarction within 6 months, NYHA Class III/IV heart failure, uncontrolled arrhythmia). * Pregnancy, lactation, or positive pregnancy test. * Other primary malignancy within 5 years, except cured non-melanoma skin cancer, carcinoma in situ, or thyroid carcinoma. * Prior anti-tumor therapy-related adverse events not recovered to ≤Grade 1 (CTCAE v6.0), except alopecia or peripheral neuropathy Grade ≤2. * Use of strong or moderate CYP3A4 inhibitors/inducers within 14 days prior to first dose. * Any other condition that in the investigator's opinion makes the participant unsuitable for the study.