Merck & Company, Inc. (NYSE:MRK), based in Rahway, New Jersey, has expanded its collaboration with Moderna, Inc. (NASDAQ:MRNA) around individualized neoantigen therapy, signaling stronger commitment to personalized cancer vaccines. The partnership is developing mRNA-4157 (V940), which is being tested with Merck's Keytruda across multiple tumor types. Earlier studies found that the combination significantly reduced the risk of recurrence or death in patients with high-risk melanoma, prompting broader development in other cancers. The move raises competitive pressure on Pfizer, Inc. (NYSE:PFE), whose partnership with BioNTech SE (NASDAQ:BNTX) includes BNT122, a personalized mRNA vaccine designed to help the immune system recognize mutations specific to a patient's tumor. Both programs aim to complement existing immunotherapies rather than replace them. The investment also reflects a wider shift among pharmaceutical companies toward oncology applications for mRNA technology after the COVID-19 pandemic. Analysts view cancer vaccines as a promising long-term use of mRNA, but clinical data may take years to mature. Future trial results, regulatory milestones and additional partnership investments could determine which companies lead the emerging field.