Merck and Moderna maintain a decade-long collaboration focused on the intismeran autogene mRNA cancer vaccine paired with Keytruda, highlighted by positive Phase 3 melanoma data in August 2026 that drove Moderna’s market value up sharply. This asset-specific partnership, along with Moderna’s independent oncology expansion and Merck’s recent acquisitions of assets like Terns Pharmaceuticals, supports the 92.3% market-implied probability against a full merger announcement in 2026. Differing business models, pipeline priorities, and valuation dynamics further reduce the likelihood of consolidation. A deeper licensing expansion or additional joint trials remain plausible but fall short of corporate-level M&A.