Merck & Co., Inc.
Acquisitions
7
Major Deals Covered
$95.2B
Disclosed Deal Value
Merck's largest disclosed acquisition here is Schering-Plough Corporation for $41B in 2009. This page covers 7 major deals from 1993 to 2026, each with its price where disclosed and the reason behind it.
| Company | Year | Price | Purpose |
|---|---|---|---|
| Schering-Plough Corporation | 2009 | $41.0B | Merck acquired Schering-Plough to diversify its pipeline beyond blockbuster drugs facing patent cliffs, gaining access to biologics manufacturing capabilities, the animal health franchise (now Merck Animal Health), and key products including Remicade and the cholesterol franchise. |
| Acceleron Pharma | 2021 | $11.5B | Merck acquired Acceleron to gain sotatercept, a first-in-class treatment for pulmonary arterial hypertension (PAH). The drug targets the underlying biology of PAH rather than just symptoms, representing a potential major shift in treating the disease. |
| Prometheus Biosciences | 2023 | $10.8B | Merck acquired Prometheus to gain PRA023, a TL1A antibody for inflammatory bowel disease (ulcerative colitis and Crohn's disease). TL1A is considered one of the most promising new targets in immunology. |
| Medco Containment Services | 1993 | $6.0B | Merck acquired Medco Containment Services, a pharmacy benefit manager, for $6 billion in 1993 to link drug development with drug distribution and gain insight into prescribing patterns. Merck spun Medco off ten years later, in 2003, as Medco Health Solutions, which Express Scripts bought in 2012. |
| Verona Pharma | 2025 | $10.0B | Added Ohtuvayre (ensifentrine), a first-in-class inhaled maintenance treatment for chronic obstructive pulmonary disease, to Merck's cardiopulmonary portfolio alongside Winrevair. |
| Cidara Therapeutics | 2026 | $9.2B | Added CD388, a late-stage long-acting drug-Fc conjugate designed to prevent influenza, expanding Merck's infectious-disease and vaccine-adjacent pipeline. |
| Terns Pharmaceuticals | 2026 | $6.7B | Added TERN-701 (now MK-4208), an allosteric BCR-ABL inhibitor in development for chronic myeloid leukemia, expanding Merck's hematology pipeline. |
2026
$9.2B
Added CD388, a late-stage long-acting drug-Fc conjugate designed to prevent influenza, expanding Merck's infectious-disease and vaccine-adjacent pipeline.
Merck paid $221.50 per share in cash, a premium of about 109% to Cidara's prior close.
Tender offer completed January 7, 2026.
2026
$6.7B
Added TERN-701 (now MK-4208), an allosteric BCR-ABL inhibitor in development for chronic myeloid leukemia, expanding Merck's hematology pipeline.
Merck recorded a one-time charge of $2.31 per share in Q2 2026, producing a GAAP quarterly loss.
Announced March 25, 2026 at $53.00 per share in cash; completed in the second quarter of 2026.
2025
$10.0B
Added Ohtuvayre (ensifentrine), a first-in-class inhaled maintenance treatment for chronic obstructive pulmonary disease, to Merck's cardiopulmonary portfolio alongside Winrevair.
Gives Merck a marketed, growing respiratory product that does not depend on Keytruda.
Completed in October 2025.
2023
$10.8B
Merck acquired Prometheus to gain PRA023, a TL1A antibody for inflammatory bowel disease (ulcerative colitis and Crohn's disease). TL1A is considered one of the most promising new targets in immunology.
Added a potentially transformative immunology asset to Merck's pipeline, diversifying beyond oncology. If approved, the drug could compete in the $50+ billion immunology market.
In late-stage clinical development. Results expected to determine whether the acquisition justifies its premium price.
2021
$11.5B
Merck acquired Acceleron to gain sotatercept, a first-in-class treatment for pulmonary arterial hypertension (PAH). The drug targets the underlying biology of PAH rather than just symptoms, representing a potential major shift in treating the disease.
Sotatercept (brand name Winrevair) was approved by the FDA in March 2024 and has become one of the most successful drug launches in recent pharmaceutical history, with analysts projecting peak annual sales of $7-10 billion.
successful acquisition. Winrevair reached blockbuster revenue run-rate within months of launch and is expected to become one of Merck's largest products, partially offsetting the eventual Keytruda patent cliff.
2009
$41.0B
Merck acquired Schering-Plough to diversify its pipeline beyond blockbuster drugs facing patent cliffs, gaining access to biologics manufacturing capabilities, the animal health franchise (now Merck Animal Health), and key products including Remicade and the cholesterol franchise.
The merger doubled Merck's revenue base, added a high-quality biologics manufacturing network, and created the Merck Animal Health division. It provided pipeline diversification at a critical moment when Merck's traditional small-molecule blockbusters were losing patent protection.
successful Merck Animal Health alone generates $5.5+ billion annually, and the biologics manufacturing capabilities acquired proved essential for later products. The integration was complex but ultimately delivered the diversification it promised.
1993
$6.0B
Merck acquired Medco Containment Services, a pharmacy benefit manager, for $6 billion in 1993 to link drug development with drug distribution and gain insight into prescribing patterns. Merck spun Medco off ten years later, in 2003, as Medco Health Solutions, which Express Scripts bought in 2012.
The acquisition proved misguided. The PBM business had different economics and culture from pharmaceutical R&D, and the vertical integration thesis did not generate the operational efficiencies Merck anticipated.
Merck spun off Medco Health Solutions to shareholders in 2003, ending its PBM experiment after about a decade.
Merck's strategy is to use Keytruda cash flow to build a broader portfolio before 2028. It moved patients toward subcutaneous Keytruda Qlex (FDA-approved September 19, 2025), expanded Keytruda into earlier-stage cancers, and bought late-stage or commercial assets: Verona Pharma for about $10 billion (completed October 2025, adding COPD drug Ohtuvayre), Cidara Therapeutics for about $9.2 billion (completed January 2026, adding influenza preventive CD388), and Terns Pharmaceuticals for about $6.7 billion (completed in Q2 2026, adding CML candidate MK-4208). Earlier deals include Acceleron ($11.5 billion, 2021), Prometheus Biosciences ($10.8 billion, 2023) and the Daiichi Sankyo ADC collaboration (up to $22 billion, 2023).
Merck makes money by selling patent-protected prescription medicines, vaccines and animal health products. The Pharmaceutical segment produced about $58.1 billion of 2025 sales, led by Keytruda/Keytruda Qlex ($31.7 billion), Gardasil ($5.2 billion), Januvia/Janumet ($2.5 billion) and Winrevair ($1.4 billion). Animal Health added about $6.4 billion from companion-animal products such as Bravecto and livestock vaccines. Sales go mainly to wholesalers, hospitals, governments and immunization programs, and the U.S. accounts for more than half of revenue. Merck reinvests heavily, spending $15.8 billion on R&D in 2025, and buys late-stage assets (Verona Pharma, Cidara, Terns) to replace revenue before patents expire.
In 2009, Merck completed a $41.1 billion reverse-merger with Schering-Plough Corporation. While done primarily to combine cholesterol drugs (Zetia and Vytorin), the merger quietly brought an early-stage, overlooked antibody molecule into Merck's pipeline: MK-3475, which became the multi-billion-dollar immunotherapy blockbuster Keytruda.
In November 2021, Merck acquired Acceleron Pharma for $11.5 billion to gain full ownership of sotatercept (now marketed as Winrevair), a major therapy for Pulmonary Arterial Hypertension (PAH), creating an essential new pillar in cardiometabolic rare diseases.
In June 2023, Merck acquired Prometheus Biosciences for $10.8 billion to secure tulisokibart (MK-7240), an anti-TL1A monoclonal antibody for ulcerative colitis and Crohn's disease. The deal instantly positioned Merck as a major player in the multi-billion-dollar global immunology and autoimmune disease market.
In 1993, Merck acquired pharmacy benefit manager (PBM) Medco Containment Services for $6.6 billion to build a vertically integrated pharmaceutical sales channel. However, regulatory scrutiny and divergent business models led Merck to spin off Medco Health Solutions in 2003, which was later acquired by Express Scripts.
In 2023, Merck acquired Imago BioSciences for $1.35 billion, adding bomedemstat (an oral lysine-specific demethylase 1 / LSD1 inhibitor) to its pipeline for treating myeloproliferative neoplasms, including essential thrombocythemia and myelofibrosis.
In 2015, Merck acquired Cubist Pharmaceuticals for $9.5 billion, securing leadership in hospital acute care and antibiotic therapies through Cubicin (daptomycin), a powerful intravenous antibiotic used to treat serious hospital-acquired Gram-positive bacterial infections.
In 2020, Merck acquired OncoImmune for $425 million in cash, gaining MK-7110 (formerly CD24Fc), a recombinant fusion protein designed to target innate immune inflammatory response pathways in severe viral and autoimmune diseases.
Merck pursues targeted, science-led bolt-on acquisitions between $1 billion and $15 billion in oncology, immunology, cardiometabolic disease, and neurology, deliberately avoiding mega-mergers that cause operational disruption and pipeline distractions.
In 2009, Merck completed a $41 billion "reverse merger" with Schering-Plough. While primarily intended to expand cardiovascular and allergy pipelines, hidden inside Schering-Plough's laboratory assets was an obscure experimental PD-1 antibody known as MK-3475. That molecule was prioritized and developed into Keytruda, which went on to generate well over $100 billion in cumulative lifetime oncology revenue.
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