TBCRC 045/AVIATOR: Comparing Trastuzumab and Vinorelbine in Combination with Avelumab or Avelumab + Utomilumab in Patients with HER2-positive Metastatic Breast Cancer (H-44362)

This study is being done to evaluate the safety and effectiveness of three different drug combinations for patients with HER2-positive metastatic breast cancer:

1. trastuzumab and vinorelbine,
2. trastuzumab, vinorelbine and avelumab
3. trastuzumab, vinorelbine, avelumab and utomilumab

The immune system is your  body's natural defense against disease - it sends T-cells throughout your body to detect and fight infections and diseases, including cancers. One way your immune system controls the activity of T-cells is through the PD-1 pathway. However, some cancer cells hide from T-cell attack by taking control of the PD-1 pathway, which stops T-cells from attacking cancer cells.

Avelumab (an IV infusion approved by the FDA for other types of cancer) is a type of drug known as an antibody, which is designed to block the PD-1 pathway and help the immune system detect and fight cancer cells. Utomilumab (investigational IV infusion) is also an antibody that is designed to stimulate the body's immune system to fight cancer cells.