This phase I trial is testing different doses (amounts) of a new targeted therapy in adults with HER2-positive cancerA Phase 1, First-In-Human, Multicenter, Open-Label, Study of GQ1001, a HER2 Targeted Antibody-Drug Conjugate, Administered Intravenously, in Adult Patients With HER2-Positive Advanced Solid Tumors

Inclusion

1. Signed informed consent form and able to comply with the protocol;
2. Male and female subjects ≥18 years of age;
3. ECOG PS of 0 or 1, the estimated life expectancy ≥ 3 months;
4. LVEF ≥ 50% as determined by echocardiography (ECHO);

5. Patients must have pathologically documented advanced/unresectable or metastatic solid tumor with HER2-positive (as defined below) that is relapsed or refractory to standard therapy or for which there is no standard therapy and progressed. Patients must have a least one measurable disease lesion. Tumor specimens to identify HER2 status should be obtained within the past 6 months.

   Definition of HER2-positive

   • Advanced/unresectable or metastatic breast cancer: immunohistochemistry (IHC) 3+, or IHC 2+ and in situ hybridization positive (ISH+)*;
   • Advanced/unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma: IHC 3+, or IHC 2+ and ISH+*;

   • Other HER2-positive advanced/unresectable or metastatic solid malignant tumor: determined by IHC, ISH, Next Generation Sequencing, or other analysis techniques as appropriate;

     • ISH: fluorescence in situ hybridization (FISH) or dual in situ hybridization (DISH); ISH positivity is defined as a ratio of ≥ 2.0 for the number of HER2 gene copies to the number of signals for CEP17. ISH assay is not required when IHC result is 3+. ISH assay should be performed to confirm HER2 positivity when IHC result is 2+.

6. Adequate organ function confirmed at screening and within 7 days before the first treatment, as evidenced by:

   Platelet count: ≥ 100,000/mm3 ; Hemoglobin : ≥ 9 g/dL; Absolute neutrophil count (ANC): ≥ 1500/mm3 ; Serum creatinine: ≤ 1.5 × ULN (upper limit of normal), or creatinine clearance ≥ 60 mL/min (using Cockcroft Gault formula) ; Aspartate aminotransferase (AST)/alanine aminotransferase (ALT) : ≤ 2.5 × ULN (≤ 5 × ULN if liver metastases are present); Total bilirubin : ≤ 1.5 × ULN (except for patients with Gilbert's Syndrome); Prothrombin time and activated partial thromboplastin time: ≤ 1.5 × ULN.

7. Adequate washout period before the first treatment as defined by:

   Major surgery: ≥ 4 weeks. Radiation therapy: ≥ 4 weeks (≥ 2 weeks for palliative stereotactic radiation therapy without abdominal). Autologous transplantation: ≥ 3 months.

   Hormonal therapy: ≥ 2 weeks or per Investigator's discretion for breast cancer patients.

   Chemotherapy or targeted therapy (including antibody drug therapy): ≥ 3 weeks (≥ 2 weeks for 5 flourouracil-based agents, folinate agents, and/or weekly paclitaxel; ≥ 2 weeks (or 5 half-lives, whichever is shorter) for tyrosine kinase inhibitors; ≥ 4 weeks for HER2-directed biologic therapies; ≥ 6 weeks for nitrosoureas or mitomycin C). Immunotherapy: ≥ 4 weeks. Strong cytochrome P450 enzyme 3A4 (CYP3A4) inhibitor: ≥ 3 elimination half-lives . Any investigational agents or treatments: ≥ 4 weeks.

8. Patients without a history of acquired immunodeficiency syndrome (AIDS)-defining opportunistic infections or with a history of AIDS-defining opportunistic infections and have not had an opportunistic infection within the past 12 months may be enrolled per the discretion of the Investigator.