This is a Phase II trial designed to determine the optimal dose and evaluate the effectiveness of TL938 and trastuzumab in treating patients with HER2+ colorectal cancer that has metastasized or recurred and is inoperable.

Inclusion Criteria:

1. Age 18 years old and above, male or female;
2. Her2-positive, RAS wild-type, unresectable or metastatic colorectal cancer and prior treatment with fluoropyrimidine, oxaliplatin, irinotecan, and an anti-vascular endothelial growth factor (VEGF) monoclonal antibody (mAb). Patients whose tumors were deficient in mismatch repair (dMMR) proteins or were microsatellite instability-high (MSI-H) must also have received an ant-programmed cell death protain-1 mAb;
3. At least one measurable lesion;
4. Eastern Cooperative Oncology Group (ECOG) score of 0, 1, or 2;
5. A minimum life expectancy of >3 months;
6. Adequate bone marrow reserve, hepatic, renal, and coagulation function;
7. Other inclusion criteria apply for participating in the Study. -

Exclusion Criteria:

1. Prior anti-HER2 targeting therapy;
2. Any systemic ant-tumor therapy such as chemotherapy and radiation therapy (including curative radiotherapy or spinal radiotherapy portion >30%) used within 3 weeks prior to enrollment; immunotherapy within 4 weeks; any palliative radiotherapy for nan-target lesions used to relieve symptoms within 2 weeks prior to enrollment;
3. Participation in another interventional clinical trial 2 weeks prior to enrollment or within 5haIf-lives from the last dose of IP (whichever is shorter);
4. Surgical operation (excluding aspiration biopsy) of main organs or a significant injury within 4 weeks prior to enrollment;
5. Any unresolved toxicities from prior therapy greater than Grada 1, at the time of screening;
6. Active central nervous system (CNS) metastases. Asymptomatic CNS metastases with no steroid use within the last 30 days prior to enrollment is eligible;
7. Any other primary malignant tumors within 3 years (except for cured skin basal cell carcinoma and carcinoma in situ of cervix, low risk cancer such as low grade prostate cancer or ductal carcinoma in situ of the breast;
8. Any active infection which has not been controlled at screening;
9. Other exclusion criteria apply for participating in the Study. -