Acquisitions, Research Collaborations and Licensing Agreements	6 Months Ended
	Jun. 30, 2025
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Acquisitions, Research Collaborations and Licensing Agreements	Acquisitions, Research Collaborations and Licensing Agreements The Company continues to pursue acquisitions and the establishment of external alliances such as research collaborations and licensing agreements to complement its internal research capabilities. These arrangements often include upfront payments; expense reimbursements or payments to the third party; milestone, royalty or profit share arrangements contingent upon the occurrence of certain future events linked to the success of the asset in development; and can also include option and continuation payments. The Company also reviews its marketed products and pipeline to examine candidates which may provide more value through out-licensing and, as part of its portfolio assessment process, may also divest certain assets. Pro forma financial information for acquired businesses is not presented if the historical financial results of the acquired entity are not significant when compared with the Company’s financial results. 2025 Transactions In July 2025, Merck entered into a definitive agreement to acquire Verona Pharma plc (Verona Pharma), a biopharmaceutical company focused on respiratory diseases, for $107 per American Depository Share (each of which represents eight Verona Pharma ordinary shares) for a total transaction value of approximately $10 billion. Through this acquisition, Merck will acquire Ohtuvayre (ensifentrine), a first-in-class selective dual inhibitor of phosphodiesterases 3 and 4 (PDE3 and PDE4), which was approved in the U.S. in June 2024 for the maintenance treatment of chronic obstructive pulmonary disease (COPD) in adult patients and is also being evaluated in clinical trials for the treatment of non-cystic fibrosis bronchiectasis. Closing of the acquisition is expected in the fourth quarter of 2025, but is subject to certain conditions, including approval under the Hart-Scott-Rodino Antitrust Improvements Act, approval of Verona Pharma’s shareholders, sanction by the High Court of Justice of England and Wales and other customary conditions. If the proposed transaction closes, the Company expects to capitalize most of the purchase price as an intangible asset for Ohtuvayre. In May 2025, Merck and Jiangsu Hengrui Pharmaceuticals Co., Ltd. (Hengrui Pharma) closed an exclusive license agreement for MK-7262 (HRS-5346), an investigational oral small molecule Lipoprotein(a) inhibitor, which is currently being evaluated in a Phase 2 clinical trial in China. Under the agreement, Hengrui Pharma granted Merck exclusive rights to develop, manufacture and commercialize MK-7262 (HRS-5346) worldwide, excluding the Greater China region. The agreement provides for an upfront payment of $200 million, which was recorded as a charge to Research and development expenses in the second quarter of 2025. Hengrui Pharma is also eligible to receive future contingent developmental milestone payments of up to $92.5 million, regulatory milestone payments of up to $177.5 million and sales-based milestone payments of up to $1.5 billion, as well as tiered royalties ranging from a mid-single-digit rate to a low-double-digit rate on future net sales of MK-7262 (HRS-5346), if approved. In March 2025, Merck acquired the Dundalk, Ireland facility of WuXi Vaccines (a wholly owned subsidiary of WuXi Biologics), which was accounted for as an asset acquisition. Merck paid $437 million at closing which, combined with previous consideration transferred under a prior manufacturing arrangement with WuXi Vaccines related to this facility, resulted in $759 million being recorded as assets under construction within Property, Plant and Equipment. There are no future contingent payments associated with the acquisition. 2024 Transactions In March 2024, Merck acquired Harpoon Therapeutics, Inc. (Harpoon), a clinical-stage immunotherapy company developing a novel class of T-cell engagers designed to harness the power of the body’s immune system to treat patients suffering from cancer and other diseases, for $765 million and also incurred $56 million of transaction costs. Harpoon’s lead candidate, gocatamig (MK-6070, formerly HPN328), is a T-cell engager targeting delta-like ligand 3 (DLL3), an inhibitory canonical Notch ligand that is expressed at high levels in small-cell lung cancer and neuroendocrine tumors. The transaction was accounted for as an asset acquisition since gocatamig represented substantially all of the fair value of the gross assets acquired (excluding cash and deferred income taxes). Merck recorded net assets of $165 million, as well as a charge of $656 million to Research and development expenses in the first six months of 2024 related to the transaction. There are no future contingent payments associated with the acquisition. In August 2024, Merck and Daiichi Sankyo expanded their existing global co-development and co-commercialization agreement to include gocatamig. See Note 3 for more information on Merck’s collaboration with Daiichi Sankyo.