This is a study of DP303c in patients with HER2-positive advanced breast cancer.
Voluntarily agree to participate in the study and sign the informed consent;
Age≥18 years old;
Patients with unresectable locally advanced or metastatic breast cancer confirmed by histology or cytology;
Confirmed to be HER2 positive by central lab (HER2-positive is defined as IHC 3+ or IHC 2+ with ISH positive);
Pregnant or breastfeeding women;
History of any other malignant tumors within three years
Has not recovered from adverse reactions caused by previous anti-tumor treatments to ≤ grade 1 or baseline (refer to NCI CTCAE 5.0);
The presence of active inflammatory bowel disease, chronic diarrhoea, short bowel syndrome or history of other gastrointestinal diseases or treatments that may affect intestinal absorption;