Efficacy and Safety of KN026 in Combination With HB1801 in the First-line Treatment of Subjects With HER2-positive Recurrent or Metastatic Breast Cancer.

This study tests a combination of two drugs — KN026 and HB1801 — as a first-line treatment for women with HER2-positive breast cancer that has returned or spread to other parts of the body. HER2-positive means the cancer cells have a protein that makes them grow faster, and these drugs specifically target that protein. **You may be eligible if...** - You are 18 or older - You have been diagnosed with HER2-positive breast cancer that is recurrent or metastatic (has spread) - You have not yet received chemotherapy or HER2-targeted therapy for this advanced stage of cancer - You are in good general health (able to carry out normal daily activities) - You have at least one measurable tumor that can be tracked on scans **You may NOT be eligible if...** - You have previously been treated with systemic therapy for metastatic breast cancer - You have active brain metastases (cancer spread to the brain) - You have serious heart, liver, or kidney problems Talk to your doctor to see if this trial is right for you.