AMGEN INC (AMGN) stock intrinsic value fair value estimate & owner earnings analysis

Amgen sells biologic medicines for bone health, cardiovascular disease, cancer, inflammation and rare disease. About 73% of 2025 product sales were in the United States. Total revenue was $36.8 billion in 2025, up 10%, and about $18.7 billion in the first half of 2026, up 8%. What the business earns. We measure cash available to all capital providers before interest, after paying for factories, counting employee stock awards as a real cost, and setting aside swings in receivables, inventories and tax timing. On that basis the business produced about $10.5 billion in 2016, roughly $10.3-11.2 billion every year through 2022, $10.5 billion in 2023, $13.4 billion in 2024 and $12.6 billion in 2025. The step up in 2024 comes from Horizon Therapeutics, bought in October 2023 for about $27 billion; we treat 2023-2025 as the business as it exists now and anchor on $12.6 billion a year (about $23 per share before interest). Two accounting judgements matter. First, large non-cash charges are not treated as costs: amortization of acquired medicines, the $1.2 billion Otezla write-down in 2025, and the roughly $3 billion of Horizon inventory fair-value charges in 2022-2024 are sunk acquisition costs. Second, we removed the 2018-2025 installments of the one-time 2017 U.S. tax-reform transition tax, which sat in tax payables and depressed reported cash flow by about $4 billion in 2023-2025. We carry almost all of 2025 capital spending ($1.86 billion) as a recurring cost. Capital spending is guided to rise again in 2026 and the first half already ran at $1.2 billion, so our first year steps down about 6% from 2025, in line with the 6% drop in business cash flow in 2025 as spending rose. What is eroding. Prolia and XGEVA, about $6.5 billion of 2025 sales, now face multiple biosimilars: in the second quarter of 2026 Prolia fell 32% and XGEVA 34%. Enbrel's Medicare price was set by the government for 2026 (net price down 22%) and U.S. biosimilar competition arrives around 2029. Otezla was selected for Medicare price setting beginning 2027, and the company already wrote the asset down. Amgen has been through this before: the multi-billion-dollar Neulasta and Epogen franchises of the mid-2010s shrank sharply while total cash generation held near $10-11 billion. What is growing. Repatha ($3.0 billion in 2025, up 36%), EVENITY, TEZSPIRE, BLINCYTO, IMDELLTRA, UPLIZNA and KRYSTEXXA are all growing at 14-115% in the latest quarter, and overall volume grew 13% in 2025. MariTide, the obesity candidate in late-stage trials, is not valued in any case because it has no sales or approval yet. A large unresolved item. The IRS is contesting how Amgen allocated profits between the U.S. and Puerto Rico in 2010-2015: about $3.6 billion of additional tax for 2010-2012 and $5.1 billion plus $2.0 billion of penalties for 2013-2015, plus interest, partly offset by about $3.1 billion of repatriation tax already paid (the headline figure reported is about $10.7 billion). The U.S. Tax Court heard the case in 2024-2025 and a ruling is expected no earlier than the second half of 2026. Amgen has accrued $4.4 billion of gross reserves for tax disputes overall, and a similar IRS examination of 2016-2018 is under way. Debt. Amgen owed about $57.3 billion at June 30, 2026 against $14.0 billion of cash, down from about $45.5 billion of net debt at year-end 2025 to about $43.3 billion. Roughly $5.4 billion falls due within twelve months, and Amgen issued $4.0 billion of new notes in early 2026. Interest runs about $2.8 billion a year, an average near 5%, so we credit about $4 billion of value for the below-market cost of the fixed-rate debt in the base and bull cases. We count $12 billion of the cash as surplus. Buybacks have stopped; the dividend is $2.52 a quarter. Bear case: about $21 per share. The business falls from $12.6 billion to about $6.8 billion by 2030 as Prolia/XGEVA, Otezla and Enbrel decline the way Neulasta did, with the newer medicines failing to replace them, then drifts to about $5 billion and holds until 2040 before fading to zero by 2050, with an extra $0.4 billion a year of tax. The IRS wins in full on 2010-2015 ($10.7 billion) and a similar $7 billion on 2016-2022, and refinancing of the debt is not cheaper than market. The business is worth about $72 billion, it owes about $57 billion of debt less $12 billion of surplus cash, and about $16 billion of tax; what is left is about $11 billion. Cash flow still covers the roughly $2.8 billion annual interest bill, but the debt absorbs nearly all the value. Base case: about $147 per share. Erosion of the products above is only partly replaced by medicines already on the market, so business cash flow drifts from $12.6 billion to about $11.0 billion by 2030, then holds flat to 2040 and fades to zero by 2050. We credit replacement only because Amgen has done exactly this repeatedly from its own research cash, which is what kept 2016-2022 flat through the Neulasta and Epogen declines; we credit no growth beyond that, no MariTide, and no market expansion. The IRS dispute costs about $5 billion, roughly the reserves already set up. The business is worth about $125 billion, it owes about $53 billion of debt (after the credit for cheap fixed-rate borrowing) less $12 billion of cash, and about $4 billion of tax; the remaining value is about $80 billion. Bull case: about $196 per share. Cash flow holds at about $12.4 billion in the first year and grows 1% a year through 2036, helped by Repatha, EVENITY, TEZSPIRE and the Tepezza and Krystexxa franchises acquired with Horizon, then holds to 2040 and fades. Amgen wins the Tax Court case and pays nothing. The business is worth about $148 billion, against the same $53 billion of debt and $12 billion of cash; the remaining value is about $106 billion. Margin-of-safety price. We are confident the business generates $10-13 billion a year because it has done so in each of ten years through patent cliffs; we are far less sure how much of the $6.5 billion Prolia/XGEVA decline, the Otezla and Enbrel price resets and the tax bill will be replaced or paid. The worst plausible outcome is the bear case: the debt is serviceable but shareholders keep little. If we are wrong about replacement or the IRS, the shares are worth roughly $20-80. The price assumes a holding period of about five years; during that period the $10 a year dividend is paid and roughly $11 billion of debt is repaid. In the base case that is roughly $135 of value plus about $55 of dividends by 2031. The margin-of-safety price is $65, a price from which the base case implies more than a 20% annual return, and from which a bear-like outcome implies a limited loss. What has changed. Prior estimates were built on a different basis and are not comparable. In the business itself, Prolia and XGEVA biosimilar erosion became visible in 2026, capital spending rose sharply, debt fell, and the IRS case is nearer a ruling. Anything that could not be fully reconciled: the share of the 2025 inventory decline that is still acquisition accounting, and how much of the $4.4 billion of tax reserves relates to the 2010-2015 years, are not separately disclosed.