Amgen makes medicines for serious diseases like cancer, arthritis, bone loss, and heart disease. Patients take these drugs repeatedly, sometimes for the rest of their lives, which means revenue keeps coming in as long as doctors keep prescribing and insurers keep paying. The company sells its products through three large wholesalers, McKesson, Cencora, and Cardinal Health, which together handle 77% of worldwide gross revenues. Amgen earns money from product sales, royalties, and partnerships, with 73% of product sales coming from the United States. The diagram below traces where the money goes.
Five years of financial data tell a story of growth layered on top of rising complexity. Revenue climbed from $26.0 billion in 2021 to $36.8 billion in 2025, a 42% increase over the period. But that growth came with a cost. Amgen paid roughly $28 billion to acquire Horizon Therapeutics in late 2023, adding drugs like TEPEZZA for thyroid eye disease and KRYSTEXXA for gout. The acquisition brought new revenue but also pushed net debt from $25.3 billion in 2021 to a peak of $53.7 billion in 2023. By 2025, Amgen had paid down enough debt to bring that figure to $45.5 billion, retiring $6.0 billion of debt in 2025 alone.
Gross margin tells a more complicated story. It was stable around 75% in 2021 and 2022, then dropped sharply to 70% in 2023 and fell further to 61.5% in 2024 as the Horizon acquisition forced Amgen to run large amounts of acquired inventory through its cost of goods at marked-up values. That accounting drag faded in 2025, and gross margin recovered to 67.2%. Free cash flow followed a similar pattern, dipping to $7.4 billion in 2023 and $8.1 billion in 2025 after peaking at $10.4 billion in 2024. The business still generates substantial cash, but the margin recovery is incomplete.
The portfolio is not moving in one direction. Some products are growing fast. Repatha, Amgen's cholesterol drug, grew 36% in both 2024 and 2025, reaching $3.0 billion in sales. TEZSPIRE, for severe asthma, grew 52% in 2025 to $1.5 billion. BLINCYTO, for blood cancer, grew 28% in 2025. EVENITY, for osteoporosis, grew 34%. These are real gains driven by more patients using the drugs. But other products are shrinking. ENBREL, once a flagship product for arthritis, fell 33% in 2025 to $2.2 billion, hit by government-mandated Medicare price cuts and higher discounts. Prolia and XGEVA lost their main patents in early 2025, and Amgen expects accelerating sales declines from biosimilar competition. Otezla faces Medicare price setting starting in 2027.
The pipeline carries both promise and fresh uncertainty. MariTide, Amgen's experimental weight loss drug that works differently from existing GLP-1 medicines, now has six global Phase 3 studies underway. Phase 2 data showed patients maintained large weight losses for a second year at lower doses, with fewer side effects over time. This is the bet-the-company moment in the pipeline. At the same time, two programs stumbled. The FDA asked Amgen to withdraw TAVNEOS from the market in January 2026 over concerns about how clinical trial data was handled, and Amgen refused, putting the drug's future in dispute. Bemarituzumab, a stomach cancer drug, was abandoned after Phase 3 data disappointed.
Amgen faces several specific, documented threats beyond normal business competition. The U.S. government's Medicare price-setting program has already reduced what Amgen earns on ENBREL, and Otezla faces the same treatment starting in 2027. Colorado has set its own price ceiling on ENBREL taking effect in 2027, and other states may follow. Separately, the IRS is challenging how Amgen allocated profits between the U.S. and Puerto Rico for the years 2010 through 2018. A tax court trial finished in January 2025, and a decision is expected no earlier than mid-2026. A loss could mean tax payments significantly larger than what Amgen has already set aside. In 2025, a jury also ordered Amgen to pay $406 million to Regeneron for how it marketed Repatha against Regeneron's competing drug Praluent.
There is also a manufacturing concentration risk most investors do not immediately see. Amgen makes most of its commercial products at a single facility in Puerto Rico and most of its clinical trial drugs at a single facility in California. If either site goes down due to a natural disaster, equipment failure, or regulatory action, Amgen cannot supply patients or run trials. The company is building out new capacity in Ohio and North Carolina, but that work is not complete.
Research and development spending jumped 22% in 2025 to $7.3 billion, driven almost entirely by later-stage clinical programs including MariTide. Amgen says it expects to keep growing this spending. That is a large and rising commitment at the same time the company is servicing $45.5 billion in net debt and watching several older products shrink.
The whole picture is a company using the cash from a large, mature medicine portfolio to fund an expensive bet on the next generation of drugs, while simultaneously paying down the debt it took on to buy new products, defending existing products from price controls and biosimilar competition, and managing a serious unresolved tax dispute. All of those threads are running at the same time.