This study is testing if a new drug, **SDX-7320**, works well when combined with a chemotherapy drug called **eribulin** for treating a type of breast cancer called **TNBC** (Triple-Negative Breast Cancer). This cancer does not have certain proteins (estrogen, progesterone, and HER2) that other breast cancers might have. The study also checks if the treatment is safe and has few or mild side effects. ### Key Points: - **Study Length & Participation**: First, 15 patients will try the new treatment. If it's safe, 40 more will join, and some will only receive eribulin. - **Eligibility**: Participants must have TNBC, be 18 or older, and meet specific health criteria, like certain blood and organ function levels. - **Exclusions**: People with more than three prior treatments for TNBC, certain health conditions, or those on certain medications cannot join. This study aims to find a better treatment option for people with TNBC and metabolic issues (like high blood sugar or a high BMI). Participants must fast before treatment days and use birth control if sexually active.