Study of the Kinesin Oral Molecular Degrader BBI-940 in Subjects With Advanced or Metastatic Breast Cancer

This study tests a new oral drug called BBI-940, which works by breaking down a protein (kinesin) that cancer cells need to divide. It is being studied in adults with advanced or metastatic breast cancer — including hormone receptor-positive breast cancer and a specific type of triple-negative breast cancer. **You may be eligible if...** - You are an adult with locally advanced or metastatic breast cancer - You have hormone receptor-positive, HER2-negative (ER+/HER2-) disease that has been treated with endocrine therapy and a CDK4/6 inhibitor - Or you have triple-negative breast cancer of the luminal androgen receptor subtype (with androgen receptor expression of at least 10%) - Your cancer can be measured on imaging scans (per RECIST criteria) - You are in good enough health to take part (ECOG 0 or 1) - You have adequate blood counts and organ function **You may NOT be eligible if...** - You have previously been treated with a kinesin inhibitor or degrader - You have a heart condition causing prolonged QT interval - You recently had a major blood clot in the lungs (within 6 weeks) - You are pregnant or breastfeeding - You have unresolved serious side effects from prior treatment Talk to your doctor to see if this trial is right for you.