This study is testing a new treatment for a type of breast cancer called **metastatic triple negative breast cancer**. This cancer doesn't have three typical proteins (ER, PR, HER2) that can be targeted by common treatments. The study is checking if a new drug, **ProAgio**, works well with another drug, **gemcitabine**. ProAgio targets a specific protein to kill cancer cells. The study is in two phases, called **Phase I/II**, which means it first checks safety and then how well the treatment works.

Participants must be **18 or older** and have had previous treatments for their cancer. They need to agree to provide tumor samples for research. The study will test different doses to find the best one. A total of **20 patients** will be involved, starting with low doses and increasing if it's safe.

Key Points:

• The study involves multiple visits for treatment and tests.
• Participants must not have used gemcitabine previously for metastatic cancer.
• Women must use birth control during and after the study.