A Study to Assess Overall Response Rate by Inducing an Inflammatory Phenotype in Metastatic BReast cAnCEr With the Oncolytic Reovirus PeLareorEp in CombinaTion With Anti-PD-L1 Avelumab and Paclitaxel - BRACELET-1 Study

The purpose of this study is to find out the possible anti-cancer effect of pelareorep in combination with chemotherapy \[paclitaxel\] and avelumab in treating a type of breast cancer called Hormone Receptor positive (HR+)/Human Epidermal Growth Factor Receptor 2 negative(HER2-) breast cancer, which is either locally advanced or has metastasized (cancer that has spread in your body). The study will investigate if pelareorep in combination with paclitaxel and avelumab is more effective than paclitaxel alone, or pelareorep and paclitaxel. The safety of the combination treatments will also be evaluated.