• Voluntarily sign the informed consent and follow the requirements of the protocol;

• No gender limit;

• Age: ≥18 years old and ≤75 years old (stage Ia); ≥18 years old (stage Ib);

• Expected survival time ≥3 months;

• The pathologic histology and/or cytology diagnosis of locally advanced or metastatic positive HER2 / low expression of the digestive tract tumor and other solid tumor;

• Consent to provide archival tumor tissue samples or fresh tissue samples from primary or metastatic lesions within 2 years;

• Must have at least one measurable lesion according to RECIST v1.1 definition;

• ECOG 0 or 1;

• Toxicity of previous antineoplastic therapy has returned to ≤ grade 1 defined by NCI-CTCAE v5.0;

⁃ No severe cardiac dysfunction, left ventricular ejection fraction ≥50%;

⁃ Organ function level must meet the requirements;

⁃ Coagulation function: international normalized ratio ≤1.5, and activated partial thromboplastin time ≤1.5ULN;

⁃ Urine protein ≤2+ or ≤1000mg/24h;

⁃ For premenopausal women with childbearing potential, a pregnancy test must be performed within 7 days before the initiation of treatment, serum pregnancy must be negative, and must be non-lactating; All the patients (no matter male or female) shall be 6 months after the end of the treatment period and full barrier precautions.