A Study to Evaluate YF550 in Participants With Locally Advanced or Metastatic Solid Tumors.

Prior treatment

• Prior or current treatment with the same class of drugs or related therapies as specified in the protocol.
• History of interstitial lung disease (ILD), radiation pneumonitis, immune-related pneumonitis, or non-infectious pneumonitis requiring corticosteroid treatment; active non-infectious pneumonitis or interstitial lung changes, including ILD, radiation pneumonitis, or immune-related pneumonitis, at screening; or hospitalization or treatment with intravenous medications for any active infection within 4 weeks before the first dose of study drug.
• Toxicities resulting from prior anticancer therapy that have not recovered to the level specified in the protocol.
• Major surgery within 4 weeks before administration of the study intervention, or the last dose of palliative radiotherapy within 2 weeks before administration of the study intervention.

Other illness

• Clinically significant cardiovascular or cerebrovascular disease.
• Gastrointestinal (GI) dysfunction or GI disease that may significantly affect the absorption or metabolism of orally administered study drug.
• Positive human immunodeficiency virus (HIV) antibody test; positive hepatitis B surface antigen (HBsAg) with hepatitis B virus deoxyribonucleic acid (HBV DNA) levels exceeding 2,500 copies/mL or 500 IU/mL; or positive hepatitis C virus (HCV) antibody test with hepatitis C virus ribonucleic acid (HCV RNA) levels exceeding the upper limit of normal at the study site.
• Other malignancies diagnosed within 5 years before enrollment.
• Severe neuropsychiatric or psychological disorders, a history of substance abuse, or a history of severe alcohol abuse.
• Any other significant clinical abnormality or medical condition that, in the investigator's judgment, may pose a safety risk to the participant or interfere with study treatment or clinical assessments.

Other

• Unstable or progressive central nervous system (CNS) metastases, carcinomatous meningitis, brainstem metastases, and/or spinal cord compression.
• Participants who are pregnant or breastfeeding, or who currently intend or plan to become pregnant or father a child.

• Aged ≥18 years, male or female, with signed informed consent.
• Histologically or cytologically confirmed locally advanced, unresectable, and/or metastatic solid tumors.
• At least one measurable lesion per RECIST 1.1.
• Availability of an adequate and qualified tumor tissue sample.
• ECOG performance status score of ≤ 1.
• Life expectancy of ≥ 12 weeks.
• Male participants and female participants of childbearing potential must agree to abstinence or use effective contraception from the time of signing the informed consent form (ICF) until 6 months after the last dose of study drug.
• Adequate organ function, as defined in the protocol.