Atezolizumab Monotherapy vs Atezolizumab Plus Cobimetinib in Liver Metastases From Colorectal Cancer

This study is for patients with metastatic colorectal cancer who are candidates for resection of metastases. This study will be conducted sequentially with 2 cohorts: 1.) Monotherapy Cohort and 2.) Combination Cohort Pre-metastatectomy * Monotherapy Cohort: The first 10 subjects will receive Atezolizumab 840 mg IV on Day 1 and Day 15 of each 28-day cycle. * Combination Cohort: The next 15 subjects will receive Atezolizumab 840 mg IV on Day 1 and Day 15 and Cobimetinib 60 mg PO on Days 1-21 of each 28-day cycle. Note: Cobimetinib must be held for the 7 days prior to metastatectomy. All subjects will be treated for 2 cycles (8 weeks) prior to metastatectomy Metastatectomy Subjects will undergo liver metastatectomy within 42 days of completion of Cycle 2 of pre-metastatectomy treatment. No study treatment is administered while the patient is healing after surgery. Post-metastatectomy Once the patient has healed from the surgery, adjuvant treatment may be administered at the discretion of the treating physician. Restaging following standards of care for this setting.