A Cancer Vaccine (STEMVAC) in Combination With Chemotherapy for the Treatment of PD-L1 Negative Metastatic Triple-Negative Breast Cancer

This study is testing a cancer vaccine called STEMVAC combined with standard chemotherapy for people with a hard-to-treat form of advanced breast cancer called triple-negative breast cancer (TNBC) that does not have a specific immune marker called PD-L1. The goal is to see if adding this vaccine helps the immune system attack the cancer. **You may be eligible if...** - You are 18 or older with confirmed triple-negative breast cancer that has spread to other parts of the body - Your tumor tests negative for PD-L1 - You have not received immunotherapy in the metastatic (spread) setting - You are otherwise healthy enough to receive chemotherapy - You are willing to have up to two biopsies during the study **You may NOT be eligible if...** - You have already received more than one line of treatment for metastatic disease - You have a serious heart condition or active autoimmune disease - You are pregnant, breastfeeding, or have HIV, hepatitis B, or hepatitis C - You have had major surgery in the past 4 weeks - You are enrolled in another treatment-based clinical trial Talk to your doctor to see if this trial is right for you.