Amgen Inc.
Biotechnology / BiopharmaceuticalsFounded 1980- Updated July 2025
Reviewed by Swet Parvadiya
Last reviewed: July 2025
CorpDigest
Amgen Inc.
Company History
Founded 1980 in Thousand Oaks, California
Last reviewed: 2025-07-15 · By Swet Parvadiya
Amgen Inc. is a Biotechnology / Biopharmaceuticals company with $33.4B in 2024 revenue and 24K employees worldwide. Amgen Inc. Was established at the dawn of the biotechnology era and has grown to become the archetype of what a successful independent biotech company can achieve. Operating from its sprawling campus in Thousand Oaks, California — a city that barely existed when Amgen moved there in 1981 and has since grown significantly in part because of Amgen's presence — the company employs approximately 24,000 people globally and maintains research, development, and manufacturing operations across the United States, Europe, and Asia-Pacific. The company is organized into research and development divisions focused on oncology, cardiovascular and metabolic diseases, inflammation, bone health, rare diseases, and neuroscience. Its commercial organization operates separate U.S. And international business units, with the U.S. Segment accounting for approximately 75% of product revenues in 2024. Amgen's manufacturing organization is among the most sophisticated in the biopharma industry, running validated large-scale biologic production at facilities in Thousand Oaks, California; West Greenwich, Rhode Island; Juncos, Puerto Rico; Breda, Netherlands; and Singapore. Amgen trades on the Nasdaq Stock Market under the ticker symbol AMGN and has been a component of the Dow Jones Industrial Average since 2020, when it replaced Pfizer in the index — a symbolic recognition of the biotech industry's ascent to the center of American commercial healthcare. With a market capitalization of approximately $153 billion and a dividend yield of approximately 3%, Amgen occupies a unique position as both a growth story and an income investment within the healthcare sector.
George B. Rathmann is widely credited as the intellectual architect of Amgen's founding culture and strategic identity. Born in 1927, Rathmann demonstrated a rare combination of scientific discipline and entrepreneurial instinct that he deployed in building Amgen from a venture-funded startup into the first biotech company to achieve genuine commercial scale. After guiding Amgen through its most formative decade — including the development and launch of Epogen and Neupogen — Rathmann stepped down as CEO in 1988 and subsequently became a director on Amgen's board. He went on to found ICOS Corporation, a biopharmaceutical company that developed Cialis (tadalafil) in collaboration with Eli Lilly, demonstrating that his entrepreneurial capabilities extended beyond Amgen. Rathmann received numerous industry honors and is remembered by colleagues as the person most responsible for establishing the cultural norms — scientific rigor, commercial ambition, and ethical accountability — that defined Amgen for decades. He passed away in 2012 at the age of 84.
William K. Bowes Jr. Was the venture capital strategist whose vision catalyzed Amgen's formation. His approach to building Amgen differed from most biotech founding stories in that he began with the commercial and organizational framework — experienced management, sufficient capital, a culture that valued both science and business — and then recruited the scientific leadership rather than the other way around. This top-down approach to company formation, unusual in an industry dominated by scientist-founders, proved prescient: Amgen's early organizational discipline helped it survive the financially devastating pre-commercial years that destroyed many of its contemporaries. Bowes remained on Amgen's board for many years after the company's commercial launch, providing governance continuity during the company's critical growth phase. His legacy in the biotech industry extends beyond Amgen — he was an early investor in multiple pioneering biotechs and helped establish the venture capital model for funding science-based startups that became the template for Silicon Valley health technology investing.
William Bowes and George Rathmann incorporated Amgen (originally Applied Molecular Genetics) on April 8, 1980, in Newbury Park, California. The company raised $19 million in venture capital funding from investors including Abbott Laboratories. Rathmann assembled an initial team of molecular biologists, biochemists, and process engineers to pursue multiple recombinant protein research programs simultaneously.
Amgen completed its initial public offering on June 17, 1983, at $18 per share, raising approximately $43 million. The IPO was conducted before the company had any meaningful commercial revenue, reflecting investor enthusiasm for the biotech sector. Scientist Fu-Kuen Lin had successfully cloned the human erythropoietin gene earlier that year, providing the scientific foundation for what would become Amgen's first blockbuster product.
Amgen entered a landmark licensing agreement with Kirin Brewery Company of Japan, granting Kirin rights to manufacture and sell recombinant EPO in Japan and Korea. The deal provided Amgen with critical cash infusion and milestone payments that extended its operational runway during the costly clinical development phase. The Kirin relationship would persist for decades, with the two companies later forming Kirin-Amgen, a joint venture that managed EPO rights in specific territories.
The FDA approved Epogen (epoetin alfa) on June 1, 1989, for the treatment of anemia in patients with chronic kidney failure undergoing dialysis. Epogen was the first commercial recombinant human erythropoietin and represented the culmination of nearly a decade of scientific and manufacturing development. The drug generated approximately $1 billion in its first year of sales, establishing a commercial record that had no precedent in the biotechnology industry and transforming Amgen from a development-stage company into a profitable commercial enterprise.
FDA approval of Neupogen (filgrastim) in February 1991 gave Amgen its second major commercial product. Neupogen stimulates white blood cell production, dramatically reducing the risk of potentially fatal infections in cancer patients undergoing chemotherapy-induced neutropenia. The drug's launch validated Amgen's strategy of focusing on serious, life-threatening conditions with large unmet medical needs and created the company's second billion-dollar product franchise within three years.
The U.S. Court of Appeals for the Federal Circuit upheld Amgen's core EPO patents against challenges by Genetics Institute, ending a decade-long intellectual property dispute that had threatened the company's commercial foundation. The ruling affirmed Amgen's rights to the recombinant EPO molecule and its production method, providing ironclad legal protection for its largest revenue source and establishing an important precedent for biologic drug patent protection.
Aranesp (darbepoetin alfa), a longer-acting version of Epogen with modified glycosylation that extends its half-life, received FDA approval, extending Amgen's erythropoietin franchise. Aranesp enabled less frequent dosing than Epogen, improving patient convenience and providing a commercial vehicle to migrate patients to a newer, higher-priced product ahead of eventual Epogen biosimilar competition. The drug generated over $3 billion annually at its peak.
Amgen completed its $16 billion acquisition of Immunex Corporation, at the time the largest acquisition in biotechnology history. The deal gave Amgen full ownership of Enbrel (etanercept), a TNF inhibitor that had been approved for rheumatoid arthritis in 1998. Enbrel became Amgen's most valuable product for the following two decades, generating peak U.S. Revenues exceeding $5 billion annually and establishing the company as a major player in the immunology and inflammation therapeutic categories.
FDA approval of Prolia (denosumab) for post-menopausal osteoporosis in June 2010, followed by XGEVA (also denosumab) for prevention of skeletal-related events in cancer patients in November 2010, gave Amgen a dominant position in bone health biologics. Denosumab, a RANK ligand inhibitor, represented a genuinely novel mechanism of action for bone resorption and quickly became a standard-of-care option, eventually generating combined revenues of nearly $5 billion annually by the early 2020s.
Amgen acquired Otezla (apremilast), a PDE4 inhibitor for plaque psoriasis and psoriatic arthritis, from Celgene Corporation for $13.4 billion. The acquisition was required by the FTC as a condition of Celgene's merger with Bristol Myers Squibb. Otezla provided Amgen with a differentiated oral small-molecule drug — unusual in its biologic-heavy portfolio — addressing a large commercially attractive immunology market where it competed directly with AbbVie's Humira and J&J's Stelara.
Amgen replaced Pfizer in the Dow Jones Industrial Average on August 31, 2020, becoming one of the index's 30 component companies. Admission to the Dow, which tracks thirty of America's largest and most historically significant public companies, represented a symbolic milestone acknowledging Amgen's status as a pillar of American industrial enterprise. The inclusion also brought passive index fund demand from the large universe of Dow-tracking investment products.
Amgen completed its acquisition of Horizon Therapeutics plc for $27.8 billion on October 6, 2023, following FTC litigation that was resolved through a consent decree requiring limited behavioral commitments. The deal gave Amgen a diversified rare disease portfolio including Tepezza (teprotumumab-trbw) for thyroid eye disease, Krystexxa (pegloticase) for refractory gout, and Uplizna (inebilizumab) for neuromyelitis optica. It represented Amgen's largest acquisition by a substantial margin and significantly reshaped its revenue profile and debt structure.
Amgen acquired Seattle-based Immunex Corporation in July 2002 for approximately $16 billion in stock, the largest acquisition in biotechnology history at that time. The primary strategic objective was to acquire full ownership rights to Enbrel (etanercept), a TNF inhibitor that Immunex had co-developed with Wyeth Pharmaceuticals and which had received FDA approval for rheumatoid arthritis in 1998. The acquisition also brought Immunex's research capabilities in cytokine biology and its scientific leadership team, including key researchers in the inflammation field.
Amgen acquired the Otezla (apremilast) business from Celgene Corporation in November 2019 for $13.4 billion in cash. The FTC required this divestiture as a condition for approving Celgene's merger with Bristol Myers Squibb. The acquisition gave Amgen an oral PDE4 inhibitor with approximately $1.6 billion in annual revenues at the time of acquisition, FDA approvals in plaque psoriasis and psoriatic arthritis, and an ongoing development program in additional indications including Behcet's disease oral ulcers.
Amgen acquired South San Francisco-based Five Prime Therapeutics in March 2021 for approximately $1.9 billion, primarily to gain access to bemarituzumab, an anti-FGFR2b antibody in development for gastric and gastroesophageal junction cancers in patients with FGFR2b overexpression. The acquisition represented Amgen's effort to build depth in solid tumor oncology beyond its existing supportive care franchise. Five Prime's technology platform and scientific expertise in receptor biology and antibody engineering were secondary motivations for the deal.
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.
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.