• A voluntarily signed and dated informed consent must be obtained from the subject in accordance with regulations and institutional guidelines before performing any protocol-related procedures other than routine care;

• Aged 18-75;

• Patients with pathologically or cytologically confirmed adenocarcinoma of the colon or rectum with evidence of locally advanced lesions or metastases that could not be resected;

• ECOG performance status score is 0-1;

• Detection of HER2-positive tumor tissue at any time before screening; HER2 positive was defined as the presence of HER2 3+ positive staining in more than 50% of tumor cells on IHC. Or patients with a HER2 score of 2+ should also be tested by FISH: HER2/CEP17 ratio ≥2.0.

• Appropriate organ function based on the following laboratory test values obtained during the screening period:

• Neutrophil count ≥1.5×109/L, platelet count ≥75×109/L, serum total bilirubin ≤ 1.5× upper normal limits, UNL), aspartate aminotransferase ≤ 2.5×UNL, alanine aminotransferase ≤ 2.5×UNL, serum creatinine ≤ 1.5×UNL;

• Previous chemotherapy including oxaliplatin, irinotecan, and fluorouracil failed, including the following:

• Subjects using oxaliplatin as adjuvant therapy should have treatment progression within 6 months of completion of adjuvant therapy; Patients who refused standard chemotherapy because of unacceptable toxicity to treatment will be admitted to the study;

• Previous or no previous anti-HER2-targeted therapy, disease progression or intolerable toxicity during or within 3 months after treatment;

• Measurable lesions, according to the Response Evaluation Criteria for Solid Tumors (RECIST) version 1.1;