Inclusion Criteria:
* Patients eligible for enrollment in this study must meet all of the following criteria:
1. Be able to understand and voluntarily sign the written informed consent form (ICF);
2. Be male or female, aged 18 to 75 years;
3. Have histologically or cytologically confirmed advanced solid tumors for which standard treatment has failed (defined as disease progression during or after treatment or intolerance to treatment-related toxicities), or for which no effective standard treatment is available, or patients who are unwilling to receive standard treatment (applicable to patients in the Phase IIa study);
4. Have histologically or cytologically confirmed advanced, recurrent, or metastatic thymic carcinoma that is unresectable and not amenable to curative radiotherapy, and have failed at least one line of chemotherapy (applicable to patients in the Phase IIb study);
* Definition of treatment failure: Disease progression during or after first-line systemic chemotherapy (which may include platinum- or taxane-based chemotherapy) or intolerance to treatment-related toxicities, with radiographic or clinical evidence confirming disease progression.
* For neoadjuvant/adjuvant therapy (chemotherapy or chemoradiotherapy), disease progression occurring during treatment or within 6 months after discontinuation of treatment will be considered failure of first-line treatment.
5. Have at least one measurable lesion according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. If a lesion that has previously received local treatment (e.g., radiotherapy, ablation, or vascular intervention) is the only measurable lesion, there must be clear radiographic evidence of disease progression in that lesion (applicable to patients in the Phase IIb study);
6. Have an Eastern Cooperative Oncology Group (ECOG) performance status of ≤1 (applicable to patients in the Phase IIa study) or ≤2 (applicable to patients in the Phase IIb study);
7. Have adequate bone marrow, hepatic, and renal function, without blood transfusion, blood product transfusion, granulocyte colony-stimulating factor (G-CSF), or other hematopoietic growth factor support within 2 weeks prior to the first dose:
* Absolute neutrophil count (ANC) ≥1.5 × 10⁹/L;
* Hemoglobin ≥9 g/dL;
* Platelet count ≥90 × 10⁹/L;
* Serum total bilirubin ≤1.5 × the upper limit of normal (ULN);
* Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2.5 × ULN (≤5 × ULN in patients with liver metastases);
* Creatinine clearance ≥50 mL/min, calculated using the Cockcroft-Gault formula (see Appendix 4);
* Urinary protein \<1+. If urinary protein is ≥1+, the quantitative 24-hour urinary protein must be \<1.0 g/24 h;
* International normalized ratio (INR) ≤1.5 and activated partial thromboplastin time (APTT) ≤1.5 × ULN;
8. For females of childbearing potential, have a negative serum or urine pregnancy test within 7 days prior to the first dose. Male patients and female patients of childbearing potential must use adequate contraceptive measures from the time of signing the ICF until 6 months after the last dose of study drug;
9. Have a body weight ≥40 kg;
10. Have a life expectancy of ≥12 weeks, as judged by the investigator.
Exclusion Criteria:
* Patients who meet any of the following criteria will be excluded from the study:
1. Have unresolved toxicities related to previous anticancer treatment that have not recovered to ≤Grade 1 according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE), except for alopecia and ≤Grade 2 peripheral neuropathy due to oxaliplatin;
2. Have had other malignancies within the past 5 years, except for adequately controlled basal cell carcinoma of the skin or carcinoma in situ of the cervix;
3. Have central nervous system (CNS) metastases requiring clinical intervention or tumor-related epilepsy. Patients with previously treated and stable CNS metastases for ≥3 months without the need for corticosteroids or antiepileptic drugs, as well as patients with asymptomatic CNS metastases, may be enrolled;
4. Have received systemic anticancer therapy within 2 weeks prior to the first dose, including chemotherapy, molecularly targeted therapy, immunotherapy, biological therapy, hormone therapy, or traditional Chinese medicine for anticancer treatment (according to the indications specified in the relevant traditional Chinese medicine package insert). Patients who have completed a 2-week washout period may be eligible for enrollment;
5. Have received definitive radiotherapy within 4 weeks prior to the first dose (including radiotherapy involving \>25% of the bone marrow), or local palliative radiotherapy for bone metastases within 2 weeks prior to the first dose;
6. Have previously received treatment with a vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitor or programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) inhibitor;
7. Have clinically uncontrolled serous effusion, such as pleural effusion that cannot be adequately controlled by drainage or other interventions;
8. Have any of the following cardiovascular conditions:
* Congestive heart failure of New York Heart Association (NYHA) functional class ≥II;
* Serious cardiac arrhythmia requiring pharmacological treatment;
* Acute myocardial infarction, severe or unstable angina pectoris, or coronary or peripheral arterial bypass surgery within 6 months prior to the first dose;
* Left ventricular ejection fraction (LVEF) \<50%;
* Corrected QT interval (QTc) \>450 ms in males or \>470 ms in females, or risk factors for torsades de pointes, such as clinically significant hypokalemia as judged by the investigator, a family history of long QT syndrome, or a family history of inherited arrhythmias (e.g., Wolff-Parkinson-White syndrome);
* Uncontrolled hypertension, defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg despite standardized antihypertensive treatment;
9. Have experienced an arterial/venous thrombotic or embolic event within 6 months prior to the first dose, such as stroke (including transient ischemic attack), deep vein thrombosis, or pulmonary embolism;
10. Have known human immunodeficiency virus (HIV) infection, active hepatitis B, or active hepatitis C. Active hepatitis B is defined as hepatitis B surface antigen (HBsAg) positivity with HBV DNA ≥10³ copies/mL or ≥200 IU/mL. Active hepatitis C is defined as positive hepatitis C virus (HCV) antibody and positive HCV RNA by polymerase chain reaction (PCR);
11. Have an active bacterial, fungal, or viral infection requiring systemic treatment within 1 week prior to the first dose;
12. Have received a strong cytochrome P450 (CYP) 2C8 and/or CYP3A4 inhibitor or a strong CYP3A4 inducer within 1 week or 5 half-lives of the drug, whichever is longer, prior to the first dose, or require continued treatment with any of these medications during the study;
13. Be unable to discontinue medications that may cause QTc prolongation or torsades de pointes (e.g., antiarrhythmic drugs) during the study;
14. Have experienced a bleeding event of ≥Grade 3 according to CTCAE within 4 weeks prior to the first dose or have a bleeding tendency. Patients with active duodenal ulcers, ulcerative colitis, intestinal obstruction, or other conditions considered by the investigator to potentially cause gastrointestinal bleeding or perforation are also excluded. Patients with a history of intestinal perforation or intestinal fistula that has not completely healed are also excluded;
15. Have multiple factors that may affect the absorption, distribution, metabolism, or elimination of oral study drug, such as inability to swallow medication, frequent vomiting, or chronic diarrhea;
16. Have any clinically significant systemic disease requiring treatment, as judged by the investigator, including but not limited to autoimmune diseases (except those requiring inhaled or topical treatment), thyroid disorders (patients with stable thyroid function on hormone replacement therapy may be enrolled), interstitial lung disease of ≥Grade 2 according to CTCAE, organ transplantation, or a history of psychiatric drug abuse, alcohol abuse, or illicit drug use;
17. Have poorly healing wounds, severe ulcers, or fractures; or have undergone major surgery (in China, major surgery is defined as Grade 3 or Grade 4 surgery according to the Administrative Measures for the Clinical Application of Medical Technologies, effective May 1, 2009) or experienced significant traumatic injury within 28 days prior to the first dose of study drug;
18. Have a known or suspected hypersensitivity to the study drug and/or any of its excipients;
19. Be pregnant or breastfeeding;
20. Be receiving treatment in another interventional clinical trial within 4 weeks prior to the first dose. Patients participating in a non-interventional clinical trial (e.g., an epidemiological study) may be eligible for enrollment. Patients who have entered the survival follow-up period of an interventional clinical trial may also be eligible for enrollment;
21. Have any other disease or medical condition that, in the investigator's judgment, is unstable or may affect patient safety or compliance with the study.
