This study is a multi-center, open, dose-increasing and dose-expanding phase I clinical study, aiming at evaluating the safety, tolerability, pharmacokinetic characteristics and preliminary anti-tumor activity of LIT-00814 tablets with different doses in China, and preliminarily evaluating the relationship between biomarkers and anti-tumor activity of LIT-00814 tablets.

This study includes two parts: Ia phase (i.e. dose escalation) and Ib phase (i.e. dose expansion).

Inclusion Criteria:

1. The subject or legal representative shall voluntarily sign the informed consent approved by the Ethics Committee before starting any screening procedure.
2. Male or female, age ≥18 years old.
3. Unresectable locally advanced or metastatic solid tumor confirmed by histology or cytology.
4. Subjects with relapsed and/or metastatic advanced solid tumors who have failed or have no standard treatment at present, or who are unable to accept standard treatment.
5. At least one target lesion.
6. ECOG score 0~1.
7. Subjects must have sufficient organ function.
8. Agree to use effective contraceptive measures within 3 months (about 90 days) from the signing of informed consent to the last administration of the study drug.

Exclusion Criteria:

1. The toxicity caused by previous treatment did not recover to ≤1 grade before the first study administration;
2. Known or symptomatic active central nervous system (CNS) metastasis or cancerous meningitis in the screening period;
3. Patients who have undergone surgery within 28 days before the first administration and have not recovered yet;
4. Suffering from uncontrolled or clinically significant cardiovascular diseases;
5. Other malignant tumors occurred within 3 years before the first administration;
6. Patients with active chronic hepatitis B, or patients with active hepatitis C, or patients with human immunodeficiency virus (HIV-Ab positive) or syphilis infection;
7. There are circumstances that affect the subjects' compliance with the research plan;
8. Other circumstances that the researcher thinks are not suitable for participating in this clinical study.