This is an investigational study. Atezolizumab is FDA approved and commercially available for the treatment of patients with locally advanced or metastatic urothelial carcinoma and patients with metastatic non-small cell lung cancer. Cobimetinib is FDA approved and commercially available for the treatment of patients with unresectable (cannot be removed with surgery) or metastatic melanoma. Eribulin is FDA approved and commercially available for the treatment of patients with metastatic breast cancer.