06 Dec 2025 SEC Filing 424B5 Financing $MRK Pending Review AI-Generated Merck & Co., Inc. (MRK) Files 424B5: Offering $8 Billion in Notes Merck & Co., Inc. (MRK) filed a 424B5 prospectus supplement for an $8 billion debt offering, with proceeds potentially funding the acquisition of Cidara Therapeutics.