A Study of PEP08 in Patients With MTAP-Del Advanced or Metastatic Solid Tumors

Inclusion Criteria: * Participants must be adults (≥18 years) and sign informed consent before undergoing any study-related procedures. * Eligible participants must have advanced or metastatic solid tumors that are not treatable with surgery or radiation, and show evidence of MTAP gene homozygous deletion or MTAP protein loss based on tumor tissue analysis. * Participants must have previously received standard treatment for their cancer type, and either experienced disease progression, be refractory, or be intolerant to such therapies. * At least one measurable lesion is required, evaluated by standard imaging criteria (RECIST v1.1). * Good general physical condition (ECOG performance status 0-1 for dose escalation; broader range allowed for other parts). * Adequate function in key organs. * Able to swallow oral medication and comply with study requirements. * Women of childbearing potential and men with reproductive potential must use effective contraception during and after the study. Exclusion Criteria: * Recent cancer treatment, immunotherapy, or investigational drugs are not allowed before starting the study. * Live vaccines received shortly before treatment are not allowed. * Previous use of drugs with similar mechanisms to the study treatment is not allowed. * Active or unstable brain or meningeal metastases, unless previously treated and stable without needing local treatment or high-dose steroids. * History of other cancers within the last 2 years, unless low-risk and treated (e.g., in situ or certain skin cancers). * Uncontrolled disease-related complications (e.g., abnormal calcium levels, fluid buildup around organs). * Active HIV, hepatitis B or C infections that are not well-controlled. * Ongoing serious infections or systemic conditions requiring isolation. * Significant heart disease, such as recent heart failure, ischemia, or arrhythmias. * History of severe digestive conditions or surgeries affecting drug absorption. * Recent major surgery. * Unresolved serious side effects from prior cancer treatment. * Currently pregnant or breastfeeding. * Poorly controlled blood pressure or lung conditions. * Other serious illnesses (e.g., severe anemia, psychiatric or social issues affecting study compliance). * Any condition that may pose a safety risk or interfere with the study, as judged by the investigator. * Known drug or substance abuse that may affect study participation. * Allergy to the study drug or any of its components.