Amgen, incorporated on April 8, 1980 as Applied Molecular Genetics, is the company that showed recombinant DNA science could be turned into a profitable medicines business. It started with three employees in a shared building in Thousand Oaks, California, as the idea of venture capitalist William K. Bowes Jr. and a group of scientific collaborators, and it hired Abbott Laboratories research executive George B. Rathmann as its first chief executive. The premise was simple and, at the time, unproven: instead of synthesizing drugs chemically, engineer living cells to make human proteins that treat disease.
Epogen and Neupogen
The first three years produced a scattered research record, including a process for making indigo dye in E. coli that reached the cover of Science. The work that mattered was assigned to Fu-Kuen Lin, who cloned the human erythropoietin gene in 1983. That clone became Epogen (epoetin alfa), approved by the FDA on June 1, 1989 for anemia in dialysis patients, which reduced the need for repeated blood transfusions. Its U.S. sales reached about US$148 million in the fiscal year ended March 31, 1990 and about US$305 million a year later. In 1985 Larry Souza and his team cloned granulocyte colony-stimulating factor, which became Neupogen (filgrastim), approved in February 1991 to reduce infection risk in chemotherapy patients. The two products made Amgen the first consistently profitable biotechnology company.
Why biologics are defensible, and why that is changing
Small-molecule drugs are chemical formulas, so a generic manufacturer can copy one exactly once the patent lapses, and the price collapses. Biologics are grown in living cells, and copying one requires rebuilding the process, so competitors file biosimilars rather than generics: a separate regulatory pathway, real clinical work and years of investment. That gave Amgen an unusually long commercial life on its older products. It is not a permanent moat. Biosimilars of Amgen medicines are now on the market, denosumab copies launched globally during 2025, and Amgen sells biosimilars of competitor biologics itself, about US$3.0 billion worth in fiscal 2025.
Buying growth: Immunex, Otezla and Horizon
Amgen completed its US$16 billion purchase of Immunex on July 16, 2002 to take full ownership of Enbrel (etanercept), then the largest deal in biotechnology. Enbrel anchored the company for close to two decades. As it aged, Amgen bought again: Onyx Pharmaceuticals for US$10.4 billion in 2013, worldwide rights to Otezla for US$13.4 billion in 2019, ChemoCentryx for US$3.7 billion in 2022 and Horizon Therapeutics for about US$27.8 billion on October 6, 2023, which added the rare disease medicines Tepezza, Krystexxa and Uplizna. The Horizon deal also left the debt Amgen is now working down, US$54.6 billion outstanding at December 31, 2025 after retiring US$6.0 billion during the year.
Where the money comes from now
Fiscal 2025 revenues were US$36.8 billion, up 10%, with GAAP net income of US$7.7 billion and US$8.1 billion of free cash flow. Fourteen products sold more than US$1 billion each. Prolia led at US$4.41 billion, followed by Repatha at US$3.02 billion, Otezla at US$2.27 billion, Enbrel at US$2.23 billion, Evenity at US$2.10 billion and XGEVA at US$2.08 billion. The split between old and new is the story: Enbrel fell 33% on a 36% lower net selling price and its negotiated Medicare price took effect on January 1, 2026, while Tezspire rose 52%, Repatha 36%, Evenity 34% and Uplizna 73%. Research spending reached US$7.3 billion, up 22%, most of the increase going to late-stage programs including MariTide, the monthly obesity candidate now in six Phase 3 MARITIME studies with a first chronic weight management readout scheduled for 2027.
