This study is testing a new drug combination for people with a kind of breast cancer called Metastatic Triple Negative Breast Cancer. The study is in two parts: Phase I and Phase II. It's checking if the new drug, ProAgio, is safe and works well when used with another drug called gemcitabine. ProAgio is an *anti-αvβ3 Integrin Cytotoxin*, which means it targets specific cells to kill cancer.

The study uses a method called *dose escalation*, which means they start with a low dose and slowly increase it to find the safest amount. Only 20 people will join at first. To be in the study, you must have tried other treatments and be 18 or older. You also need to have certain health conditions checked, like blood and organ health.

• The study is for people who have tried other treatments.
• Participants must be willing to undergo tumor biopsies.
• Requires using contraception during and after the study.

People who have had gemcitabine before or have certain health issues, like heart problems, cannot join. Pregnant or nursing women are also excluded to avoid risks to babies.