Trastuzumab Deruxtecan (DS-8201a) is a medication used in this clinical trial. It is an anti-HER2-antibody drug conjugate, which means it is designed to target and attach to HER2 proteins on cancer cells. Once attached, it delivers a chemotherapy drug directly to the cancer cells, helping to destroy them. This medication is being tested for its effectiveness in treating HER2-positive, unresectable, and/or metastatic breast cancer in patients who have already been treated with trastuzumab and a taxane.

Ado-Trastuzumab Emtansine (T-DM1) is another medication involved in the trial. It is also an anti-HER2-antibody drug conjugate, similar to trastuzumab deruxtecan. It works by binding to the HER2 proteins on cancer cells and delivering a chemotherapy drug to these cells. This medication is used as a comparison to evaluate the effectiveness of trastuzumab deruxtecan in the study. It is intended for patients with HER2-positive, unresectable, and/or metastatic breast cancer who have previously received treatment with trastuzumab and a taxane.

Metastatic breast cancer – This is a type of breast cancer that has spread beyond the breast to other parts of the body, such as the bones, liver, lungs, or brain. It is considered an advanced stage of breast cancer, often referred to as stage IV. The disease progresses as cancer cells travel through the bloodstream or lymphatic system to form new tumors in other organs. Symptoms can vary depending on where the cancer has spread, but may include bone pain, difficulty breathing, or neurological symptoms. The progression of metastatic breast cancer can be influenced by factors such as the cancer’s hormone receptor status and HER2 status. It is a chronic condition that requires ongoing management to control the spread and alleviate symptoms.