Herombopag Treated T-DM1 Induced Platelet Reduction

This study tests a drug called herombopag — which helps the body produce more platelets (blood cells that help with clotting) — in breast cancer patients who have developed low platelet counts (thrombocytopenia) as a side effect of a treatment called T-DM1. **You may be eligible if...** - You are 18 to 75 years old - You have breast cancer that was previously treated with neoadjuvant anti-HER2 therapy, and you are now receiving T-DM1 as adjuvant therapy - You developed a significant drop in platelet count (grade 2 or higher) during T-DM1 treatment **You may NOT be eligible if...** - You have a platelet disorder unrelated to your cancer treatment - You have liver disease or significant blood clotting problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.