Study of Denikitug (GS-1811) Given Alone or With Nivolumab or With Chemotherapy in Adults With Advanced Colorectal Cancer

Key Inclusion Criteria: Medical History/Physical Characteristics * Histologically or cytologically confirmed unresectable, recurrent, or locally advanced or metastatic microsatellite stable colorectal cancer (MSS CRC) (adenocarcinoma, excluding appendix cancer). * Documented MSS or proficient mismatch repair (pMMR) disease by local assessment using a validated polymerase chain reaction (PCR) (microsatellite status) and/or immunohistochemistry (IHC) mismatch repair (MMR) assay is required. * Has received up to 2 prior lines of systemic therapy for advanced or metastatic CRC, which must have included at least fluoropyrimidine-, oxaliplatin-, irinotecan-based chemotherapies if indicated; and if applicable: anti-vascular endothelial growth factor (VEGF) therapy, anti epidermal growth factor receptor (EGFR) therapy, encorafenib or adagrasib/sotorasib. * Documented progressive disease (PD) by computed tomography (CT) or magnetic resonance imaging (MRI) during or after the most recent therapy per RECIST Version 1.1 criteria by investigator assessment. * Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1. Laboratory Assessments * Have adequate organ function. Key Exclusion Criteria with: Medical Conditions/History: * Significant cardiovascular disease. * History of autoimmune disease or active autoimmune disease that has required systemic treatment within 2 years. * History of (noninfectious) pneumonitis/interstitial lung disease or current pneumonitis/ interstitial lung disease. * History of gastrointestinal (GI) perforation, permanent ileostomy, abdominal abscess or fistula within 6 months, active or uncontrolled GI bleeding within 4 weeks, or any condition associated with significant risk of bleeding or perforation (eg, untreated varices, tumor erosion, recent GI surgery). Prior/Concurrent Therapy or Clinical Study Experience Prior treatment with: * Trifluridine-tipiracil, regorafenib, or fruquitinib. * Any immuno-oncology therapy. * Anticancer biologic agent within 4 weeks prior to randomization or have had prior chemotherapy, targeted small molecule therapy, or radiation therapy within 2 weeks prior to randomization and have not recovered (ie, Grade 2 or less) from AEs from prior anticancer therapy at the time of randomization. Individuals in observational studies are eligible. * Allogeneic tissue/solid organ transplantation, including allogeneic stem cell transplantation. Exception: prior corneal transplant without requirement for systemic immunosuppressive agents is allowed. Note: Other protocol defined Inclusion/Exclusion criteria may apply.