A Study to Investigate BGB-3245 (Brimarafenib) With Panitumumab in Participants With Advanced or Metastatic RAS Mutant Colorectal and Pancreatic Ductal Cancers

Key Inclusion Criteria: 1. Participants with histologically confirmed advanced or metastatic solid tumors who have had documented disease progression by RECIST criteria during or after at least 1 prior line of systemic anticancer therapies in the representative population or are unable to receive standard of care therapy(ies) as noted by local guidelines. 2. Part 1 (Dose Finding): Participants with CRC with a known mutation status by local testing and tumor harboring an oncogenic mutation of BRAF, KRAS, or NRAS in the archival tumor sample or fresh tumor biopsy. 3. Part 2 (Dose Expansion): Participants must have a known mutation status by local testing and meet one of the following criteria according to the group they are enrolled into: Group 1: Participants with CRC that harbors KRAS or NRAS mutations in the archival tumor sample or fresh tumor biopsy. Group 2: Participants with PDAC that harbors KRAS mutations in the archival tumor sample or fresh tumor biopsy. 4. Participants must provide archival tumor tissue or a fresh tumor biopsy for retrospective mutation status analysis. 5. Participants must have radiologically measurable disease as defined per RECIST v1.1 at screening. 6. Eastern Cooperative Oncology Group performance status of ≤1 at screening. 7. Adequate hematologic and organ function, as indicated by defined laboratory values, prior to Cycle 1 Day 1. 8. Adequate cardiac function. Key Exclusion Criteria: 1. Participants receiving cancer therapy (chemotherapy or other systemic anticancer therapies, immunotherapy, radiation therapy, or surgery) at the time of Cycle 1 Day 1. 2. Active infection requiring systemic treatment at the start of the study treatment. 3. Clinically significant cardiovascular disease and / or events within 6 months of signing the informed consent form. 4. Participants with toxicities that have not recovered to Grade ≤1 or stabilized and those Grade 2 toxicities listed as permitted in other eligibility criteria. 5. Participants with a history of pneumonitis or interstitial lung disease. 6. Participants with immune-related toxicities that have not resolved with appropriate management. 7. History or presence of gastrointestinal disease or other condition known to interfere with the absorption of drugs. 8. History of ulcerative colitis or Crohn's disease or protracted and ongoing immune-mediated diarrhea from prior checkpoint inhibitor use. 9. History of corneal perforation, keratitis, or severe dry eye. 10. Current evidence of symptomatic central nervous system metastases, leptomeningeal carcinomatosis, or untreated spinal cord compression. 11. Any active malignancy ≤3 years before Cycle 1 Day 1 except for the specific cancer under investigation in this study and any localized or noninvasive cancer that has been treated curatively. 12. Known hypersensitivity to rapidly accelerated fibrosarcoma (RAF) inhibitors, anti-epidermal growth factor receptor (EGFR) monoclonal antibodies, or their excipients. 13. Any known history of Grade ≥3 toxicity lasting \>14 days from another RAF, mitogen activated protein kinase, extracellular signal-regulated kinase, or anti-EGFR antibody inhibitor requiring discontinuation of treatment from these drugs. 14. Receiving any treatment with a strong cytochrome P450 3A4 (CYP3A4) inhibitor or inducer ≤14 days (or 5 half-lives, whichever is longer) before Cycle 1 Day 1 and until completion of dosing with BGB-3245 for at least 5 half-lives. NOTE: Other protocol defined Inclusion/Exclusion criteria apply. Summary of key criteria provided.