A Phase II Study of HLX22 in Combination With Trastuzumab and Chemotherapy in HER2-Positive Locally Advanced or Metastatic Breast Cancer Patients

Inclusion Criteria:

• Aged ≥ 18 years (or the legal age of adulthood per country-specific regulation) at the time of signing the ICF, male or female.
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or - Life expectancy of ≥ 6 months.
• Histologically confirmed breast cancer with radiologically or otherwise documented locally advanced unresectable and/or metastatic disease.
• HER2 positive confirmed by central laboratory.
• Hormone receptor (HR) status confirmed by local laboratory.
• Patients who have progressed after treatment containing within HER2 ADC
• Presence of at least one measurable lesion according to the RECIST v1.1.
• Adequate organ function

Exclusion Criteria:

• History of any other malignancy within 2 years prior to signing the ICF.
• Prior use of doxorubicin with a cumulative in vivo dose of > 360 mg/m2.
• Adverse events from prior anti-tumor treatment that have not resolved to Grade ≤ 1 or baseline level according to CTCAE v6.0.
• Uncontrolled or severe cardiovascular disease.
• History of cerebrovascular accident within 6 months prior to randomization.
• Current (non-infectious) interstitial lung disease (ILD)/pneumonia that requires steroid treatment.
• Active infection.
• Active tuberculosis.
• Presence of spinal cord compression or clinically symptomatic central nervous system metastases.
• Receipt of systemic anti-tumor treatment and immunotherapy, within 4 weeks prior to randomization
• Pregnant or lactating women or women who plan to become pregnant during the study period.
• History of immunodeficiency or history of organ transplantation.