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Amgen Inc.

Biotechnology / BiopharmaceuticalsFounded 1980
Reviewed by Swet Parvadiya
Company data updated: September 2026

Acquisitions

Amgen Acquisitions

7

Major Deals Covered

$73.6B

Disclosed Deal Value

What are Amgen's biggest acquisitions?

Amgen's largest disclosed acquisition here is Horizon Therapeutics plc for $27.8B in 2023. This page covers 7 major deals from 2002 to 2023, each with its price where disclosed and the reason behind it.

Major deals covered
7
Largest deal
Horizon Therapeutics plc ($27.8B)
First deal
2002
Most recent
2023
CompanyYearPricePurpose
Immunex Corporation2002$16.0BAmgen acquired Seattle-based Immunex Corporation for about US$16 billion in stock and cash, completing the deal on July 16, 2002. It was the largest acquisition in biotechnology to that point. The objective was full ownership of Enbrel (etanercept), a TNF inhibitor that Immunex had developed with Wyeth and that the FDA approved for rheumatoid arthritis in 1998. The deal also brought Immunex cytokine biology research and its scientific staff.
DeCODE Genetics2012$415.0MAmgen acquired Reykjavik, Iceland-based deCODE Genetics in December 2012 for approximately $415 million. DeCODE had built one of the world's largest and most scientifically valuable human genetics databases, with genetic and health data from a substantial proportion of Iceland's 320,000-person population. The acquisition gave Amgen access to this unique genomic resource as a tool for identifying genetic variants associated with human diseases variants that could point to novel drug targets or help predict which patient populations would respond to specific therapies.
Onyx Pharmaceuticals, Inc.2013$10.4BAmgen agreed in August 2013 to buy South San Francisco based Onyx Pharmaceuticals for US$125 per share, a purchase price of US$10.4 billion or US$9.7 billion net of estimated Onyx cash, and completed the tender offer on October 1, 2013. The main asset was Kyprolis (carfilzomib), a proteasome inhibitor for multiple myeloma, which Amgen took worldwide. The deal also brought royalties on Bayer's Nexavar and Stivarga.
Celgene Otezla Business2019$13.4BAmgen agreed in August 2019 to acquire worldwide rights to Otezla (apremilast) from Celgene Corporation for US$13.4 billion in cash, or about US$11.2 billion net of the present value of US$2.2 billion of anticipated future cash tax benefits, and closed the transaction on November 21, 2019. The FTC had required the divestiture as a condition of the Bristol Myers Squibb merger with Celgene. Otezla was an oral PDE4 inhibitor with roughly US$1.6 billion of annual sales, approved in plaque psoriasis and psoriatic arthritis.
Five Prime Therapeutics2021$1.9BAmgen agreed on March 4, 2021 to buy South San Francisco based Five Prime Therapeutics for US$38.00 per share, an equity value of about US$1.9 billion, and completed the tender offer and merger on April 16, 2021. The lead asset was bemarituzumab, a first-in-class anti-FGFR2b antibody ready for Phase 3 in gastric and gastroesophageal junction cancer. Five Prime's work in receptor biology and antibody engineering was a secondary motivation.
ChemoCentryx, Inc.2022$3.7BAmgen acquired ChemoCentryx for US$52 per share in cash, aggregate merger consideration of about US$3.7 billion, completing the deal on October 20, 2022. The asset was Tavneos (avacopan), an orally administered selective complement 5a receptor inhibitor that the FDA approved in October 2021 as adjunctive therapy for adults with severe active ANCA-associated vasculitis. Three early-stage chemoattractant receptor programs came with it.
Horizon Therapeutics plc2023$27.8BAmgen acquired Horizon Therapeutics plc in October 2023 for approximately $27.8 billion in the largest acquisition in Amgen's history. The deal's strategic purpose was threefold: diversifying into rare diseases with high-pricing, durable commercial profiles; acquiring Tepezza's leadership position in thyroid eye disease, a condition affecting an estimated 200,000 patients in the U.S. With a treatment market estimated to ultimately exceed $3 billion; and adding Krystexxa's dominance in refractory gout a condition affecting approximately 100,000 patients annually who do not respond to standard urate-lowering therapy.
What companies has Amgen bought?
Major acquisitions by Amgen documented here include Horizon Therapeutics plc (2023), Immunex Corporation (2002), Celgene Otezla Business (2019), Onyx Pharmaceuticals, Inc. (2013) and ChemoCentryx, Inc. (2022).
What is Amgen's most recent acquisition?
The most recent Amgen acquisition documented here is Horizon Therapeutics plc, in 2023, for $27.8B.

Horizon Therapeutics plc

2023

$27.8B

Why

Amgen acquired Horizon Therapeutics plc in October 2023 for approximately $27.8 billion in the largest acquisition in Amgen's history. The deal's strategic purpose was threefold: diversifying into rare diseases with high-pricing, durable commercial profiles; acquiring Tepezza's leadership position in thyroid eye disease, a condition affecting an estimated 200,000 patients in the U.S. With a treatment market estimated to ultimately exceed $3 billion; and adding Krystexxa's dominance in refractory gout a condition affecting approximately 100,000 patients annually who do not respond to standard urate-lowering therapy.

Impact

The Horizon medicines reshaped the revenue mix, adding roughly US$3.5 billion of annualised revenue in 2024 and about US$4.6 billion in fiscal 2025 across Tepezza, Krystexxa, Uplizna and the ultra-rare products. The cost was the balance sheet: debt outstanding was US$60.1 billion at the end of 2024 and US$54.6 billion at December 31, 2025 after US$6.0 billion of retirements, with US$2.8 billion of net interest expense in fiscal 2025. The FTC consent decree also imposed ongoing compliance obligations.

Outcome

Two years after closing, the Horizon assets are growing. Uplizna rose 73% in fiscal 2025 to US$655 million after approvals in IgG4-related disease and generalized myasthenia gravis, Krystexxa rose 13% to US$1.34 billion, and Tepezza rose 3% to US$1.90 billion. The ultra-rare group declined 5% as Ravicti met generic competition. Investor attention has shifted from the acquisition premium to the pace of deleveraging.

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ChemoCentryx, Inc.

2022

$3.7B

Why

Amgen acquired ChemoCentryx for US$52 per share in cash, aggregate merger consideration of about US$3.7 billion, completing the deal on October 20, 2022. The asset was Tavneos (avacopan), an orally administered selective complement 5a receptor inhibitor that the FDA approved in October 2021 as adjunctive therapy for adults with severe active ANCA-associated vasculitis. Three early-stage chemoattractant receptor programs came with it.

Impact

Tavneos added an oral medicine to the inflammation and nephrology portfolio and a rare autoimmune indication that fit the rare disease commercial model Amgen later expanded with Horizon. Sales grew 62% in fiscal 2025 to US$459 million.

Outcome

The program is now contested. On January 16, 2026 the FDA asked ChemoCentryx to withdraw Tavneos from the U.S. market, citing the process used to re-adjudicate primary endpoint results for 9 of the 331 patients in the pivotal trial together with the known hepatotoxicity risk. Amgen told the agency on January 28, 2026 that it did not intend to withdraw the medicine and is working with the FDA on a path forward.

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Five Prime Therapeutics

2021

$1.9B

Why

Amgen agreed on March 4, 2021 to buy South San Francisco based Five Prime Therapeutics for US$38.00 per share, an equity value of about US$1.9 billion, and completed the tender offer and merger on April 16, 2021. The lead asset was bemarituzumab, a first-in-class anti-FGFR2b antibody ready for Phase 3 in gastric and gastroesophageal junction cancer. Five Prime's work in receptor biology and antibody engineering was a secondary motivation.

Impact

Bemarituzumab gave Amgen a biomarker-defined solid tumor program to set beside its supportive-care oncology business, selecting patients by FGFR2b overexpression rather than by tumor type alone.

Outcome

On June 30, 2025 Amgen reported that the Phase 3 FORTITUDE-101 trial of first-line bemarituzumab plus mFOLFOX6 chemotherapy met its primary endpoint of overall survival at a pre-specified interim analysis in FGFR2b-positive, HER2-negative gastric and gastroesophageal junction cancer. That is the first positive Phase 3 result for an FGFR2b-targeted antibody and the clearest evidence so far that the acquisition will pay for itself.

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Celgene Otezla Business

2019

$13.4B

Why

Amgen agreed in August 2019 to acquire worldwide rights to Otezla (apremilast) from Celgene Corporation for US$13.4 billion in cash, or about US$11.2 billion net of the present value of US$2.2 billion of anticipated future cash tax benefits, and closed the transaction on November 21, 2019. The FTC had required the divestiture as a condition of the Bristol Myers Squibb merger with Celgene. Otezla was an oral PDE4 inhibitor with roughly US$1.6 billion of annual sales, approved in plaque psoriasis and psoriatic arthritis.

Impact

Otezla diversified Amgen into dermatology and rheumatology and gave it a significant oral small-molecule product for the first time, which suited a commercial organization built around specialists. Sales grew from about US$1.6 billion at acquisition to US$2.27 billion in fiscal 2025.

Outcome

Otezla has held formulary access against newer biologics and JAK inhibitors, but the economics have changed: after Otezla was selected for Medicare price setting under the Inflation Reduction Act, Amgen recorded US$1.2 billion of intangible asset impairment charges in 2025.

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Onyx Pharmaceuticals, Inc.

2013

$10.4B

Why

Amgen agreed in August 2013 to buy South San Francisco based Onyx Pharmaceuticals for US$125 per share, a purchase price of US$10.4 billion or US$9.7 billion net of estimated Onyx cash, and completed the tender offer on October 1, 2013. The main asset was Kyprolis (carfilzomib), a proteasome inhibitor for multiple myeloma, which Amgen took worldwide. The deal also brought royalties on Bayer's Nexavar and Stivarga.

Impact

Kyprolis gave Amgen a hematology-oncology franchise it had not built internally, and the Onyx commercial and development staff became the base of its solid tumor and hematology organization. Kyprolis generated US$1.41 billion of sales in fiscal 2025, down 6% year over year on lower volume.

Outcome

Kyprolis has not reached the peak sales some analysts projected in 2013, but it remains a billion-dollar product more than a decade later and the oncology organization built around it went on to launch Blincyto, Lumakras and Imdelltra.

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DeCODE Genetics

2012

$415M

Why

Amgen acquired Reykjavik, Iceland-based deCODE Genetics in December 2012 for approximately $415 million. DeCODE had built one of the world's largest and most scientifically valuable human genetics databases, with genetic and health data from a substantial proportion of Iceland's 320,000-person population. The acquisition gave Amgen access to this unique genomic resource as a tool for identifying genetic variants associated with human diseases variants that could point to novel drug targets or help predict which patient populations would respond to specific therapies.

Impact

DeCODE has become one of Amgen's most intellectually important research assets, generating multiple drug discovery insights including confirmation of the PCSK9 target's role in cardiovascular disease protection (natural loss-of-function variants in PCSK9 are associated with reduced cardiovascular event rates, a biological observation that informed Repatha's development). DeCODE's published genomic discoveries have appeared in the world's most prestigious scientific journals, enhancing Amgen's scientific credibility.

Outcome

The deCODE acquisition is widely viewed as one of the most prescient moves in biopharmaceutical history. For an acquisition cost of $415 million, Amgen gained a research asset that contributed scientifically to the development of Repatha a drug generating over $2 billion annually and continues to generate novel drug target hypotheses across multiple therapeutic categories. The acquisition established Amgen as a pioneer in genetics-informed drug discovery, a research methodology now standard across the pharmaceutical industry.

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Immunex Corporation

2002

$16.0B

Why

Amgen acquired Seattle-based Immunex Corporation for about US$16 billion in stock and cash, completing the deal on July 16, 2002. It was the largest acquisition in biotechnology to that point. The objective was full ownership of Enbrel (etanercept), a TNF inhibitor that Immunex had developed with Wyeth and that the FDA approved for rheumatoid arthritis in 1998. The deal also brought Immunex cytokine biology research and its scientific staff.

Impact

The Immunex acquisition transformed Amgen from a company dependent on its EPO and G-CSF franchises into a broadly diversified biologic company with a major position in the immunology and inflammation market. Enbrel became Amgen's largest revenue contributor within years of the acquisition, eventually generating peak U.S. Revenues exceeding $5 billion annually. The deal also gave Amgen the Bothell, Washington research and manufacturing facilities that supported its inflammation biology research for years.

Outcome

The Immunex deal is generally judged one of the most value-creating transactions in the industry. Despite a premium that drew analyst skepticism, Enbrel revenues repaid the purchase price within roughly five to six years. Enbrel still generated US$3.32 billion of sales in 2024 and US$2.23 billion in fiscal 2025, more than two decades later, although Medicare Part D redesign and 340B mix have now cut its net price sharply.

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Amgen Inc.'s Growth & Acquisition Strategy

Amgen's growth plan has two parts: scale the newer medicines and buy what the pipeline does not supply. Recent launches and acquired products drove the 10% revenue growth in fiscal 2025, with Tezspire up 52% to US$1.48 billion, Repatha up 36% to US$3.02 billion, Evenity up 34% to US$2.10 billion, Uplizna up 73% to US$655 million and Imdelltra reaching US$627 million in its second year. The company is pushing into obesity with MariTide, now in six Phase 3 MARITIME studies, and runs a biosimilars business that produced about US$3.0 billion of fiscal 2025 sales across Pavblu, Mvasi, Amjevita and Wezlana.

How Amgen Inc. Makes Money

Amgen operates a high-risk, high-reward biopharmaceutical business model. It spends heavily on research to discover and engineer new biologic drugs: US$7.3 billion in fiscal 2025, or 20.7% of product sales. Once a drug is approved by the FDA, Amgen secures a patent, granting them a temporary monopoly to sell the drug at a premium price. Because biologic drugs are grown from living cells rather than chemically synthesized, they are much harder for competitors to copy, resulting in slightly longer and more defensible monopolies than traditional pills.

Amgen Acquisitions FAQ

When and for how much did Amgen acquire Horizon Therapeutics?

Amgen completed its acquisition of Horizon Therapeutics on October 6, 2023 for US$116.50 per share in cash, an equity value of about US$27.8 billion, the largest acquisition in its history.

What was the strategic importance of acquiring Immunex Corporation in 2002?

Amgen acquired Seattle-based Immunex Corporation in July 2002 for $16 billion in stock and cash, gaining full ownership of blockbuster TNF inhibitor Enbrel (etanercept), which became one of the bestselling biologic drugs in global history.

When did Amgen acquire Onyx Pharmaceuticals and what drug did it add?

Amgen acquired Onyx Pharmaceuticals in October 2013 for $10.4 billion in cash, adding multiple myeloma proteasome inhibitor Kyprolis (carfilzomib) to anchor its expanding hematology-oncology commercial portfolio.

When did Amgen acquire Celgene's Otezla (apremilast)?

In November 2019, Amgen acquired oral psoriasis treatment Otezla from Celgene for $13.4 billion in cash, a divestiture mandated by the FTC to allow Bristol Myers Squibb to complete its acquisition of Celgene.

When did Amgen acquire deCODE Genetics and how has it shaped R&D?

Amgen acquired Reykjavik-based deCODE Genetics in December 2012 for $415 million in cash, integrating population-scale human genomics into target validation and doubling the clinical success rate of early discovery programs.

When and for how much did Amgen acquire ChemoCentryx?

In October 2022, Amgen acquired ChemoCentryx for $3.7 billion in cash, gaining Tavneos (avacopan), an orally administered first-in-class treatment for severe active anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis.

What oncology platform did Amgen acquire through Micromet in 2012?

Amgen acquired German biotech Micromet in January 2012 for $1.16 billion, gaining the proprietary Bispecific T-cell Engager (BiTE) antibody platform and lead therapy Blincyto (blinatumomab).

When did Amgen acquire Five Prime Therapeutics?

Amgen agreed to buy Five Prime Therapeutics on March 4, 2021 for US$38.00 per share, an equity value of about US$1.9 billion, and completed the deal on April 16, 2021. The lead asset was bemarituzumab, a first-in-class anti-FGFR2b antibody for FGFR2b-positive gastric and gastroesophageal junction cancer.

What companies has Amgen acquired?

Amgen aggressively acquires smaller biotech firms to replenish its pipeline, most notably executing a massive $27.8 billion buyout of rare-disease specialist Horizon Therapeutics.

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Content is for informational purposes only. Not financial advice. Data sourced from SEC filings, annual reports, and public records. See our full disclaimer and methodology.