Amphastar Pharmaceuticals, Inc. (AMPH) stock intrinsic value fair value estimate & owner earnings analysis

Amphastar Pharmaceuticals makes and sells more than 25 prescription drugs, mostly technically difficult injectables and inhalation products, plus the over-the-counter asthma inhaler Primatene MIST. Revenue in 2025 was $719.9 million. The largest products were BAQSIMI nasal glucagon ($185.4 million), Primatene MIST ($108.7 million), epinephrine ($70.6 million), injectable glucagon ($69.1 million) and lidocaine ($56.5 million). About 95% of sales are booked in the United States, largely through three wholesalers (McKesson, Cencora and Cardinal Health, together 65% of 2025 revenue); about 5% is booked by its French operation (up from $4.7 million in 2023 to $35.3 million in 2025). The company also owns a manufacturing and ingredient subsidiary in Nanjing, China, and does contract manufacturing, research, distribution and licensing business with Nanjing Hanxin, a company in which Amphastar's Dr. Jack Zhang and Dr. Mary Luo hold an ownership interest. China itself contributes under 1% of revenue. What the business earns. We measure the cash an owner could take out each year: operating cash flow, less stock-based pay (a real cost), less the capital spending needed to keep the plants running, with temporary swings in inventories, receivables, payables and tax balances stripped out. Lease payments are treated as an operating cost. On that basis the company earned $2.99 per share in 2023, $3.20 in 2024 and $3.20 in 2025. We start from $3.20, the median of those three years, because the June 2023 purchase of BAQSIMI from Eli Lilly made this a different and much more profitable business; before it, owner earnings never exceeded $1.56 per share. Two 2025 one-offs roughly cancel: a $23.1 million payment on a personal-injury jury verdict and a $28.7 million tax benefit from the 2025 federal tax law that let the company deduct research costs it had previously been required to capitalize. Roughly $25 million a year of intangible amortization, mostly from the BAQSIMI purchase, is an accounting charge on a purchase already paid for, so it is added back; the fact that some older products are losing value is carried in the growth path instead. Where it is heading. The product mix is shifting. Injectable glucagon fell 36% in 2025 and epinephrine 25% on competition and lower prices, and management expects glucagon to keep declining; the company attributes the fall to competition and a shift toward ready-to-use products such as BAQSIMI. Offsetting that, BAQSIMI's underlying sales grew about 12% in 2025, Primatene MIST has grown from $89.3 million in 2023 to $108.7 million, and a run of newly approved generics is ramping: albuterol inhaler (launched August 2024), iron sucrose (August 2025), a teriparatide pen (December 2025) and an ipratropium inhaler (approved February 2026). Research spending is rising ($85.8 million in 2025) for insulin biosimilars and inhalation products. The first half of 2026 was weaker: operating income fell to $53.4 million from $79.5 million, almost all of it in the first quarter, when gross margin dropped to about 41% from roughly 50%. We could not determine the cause from the materials available to us; the second quarter was close to the prior year. Owner earnings per share were flat in 2025 (the total fell about 7%, offset by share repurchases), so the base case starts with a decline, not growth. Base case, $39.03 per share: owner earnings dip to about $2.95 in 2026 and $2.85 in 2027 as glucagon and epinephrine keep eroding, then recover to about $3.15 by 2030 as BAQSIMI, Primatene MIST and the new launches fill the gap. They hold there through 2045, supported by a demonstrated ability to win approvals for hard-to-copy generics (four in the past two years), and then fade to zero over the following decade. Bear case, $18.81 per share: glucagon and epinephrine keep sliding, BAQSIMI stalls against competing ready-to-use glucagon products, the three large wholesalers use their bargaining power on price, and the $250 million Wells Fargo term loan due June 2028 and $345 million of 2.00% convertible notes due 2029 are refinanced at much higher interest rates. Primatene MIST also depends on a propellant that federal law is phasing down, a supply risk the company discloses. Owner earnings fall to about $1.85 per share by 2029, stay there through 2035, then fade to zero over the next ten years. Bull case, $54.03 per share: BAQSIMI keeps growing near its recent pace, Primatene MIST keeps gaining volume, the new generics ramp well and the glucagon decline levels off. Owner earnings reach about $4.10 by 2030 and $4.75 by 2035, hold for a decade, then fade. BAQSIMI carries up to $575 million of sales-based milestone payments to Lilly, which would absorb part of this upside if sales climb high enough. The insulin biosimilar and other candidates still awaiting approval are left out of every case, because none is approved yet. Debt. The company had about $620 million of debt against about $283 million of cash and short-term investments at the end of 2025. Interest is already paid out of the cash flow we measure, so the debt is not subtracted again; its risk sits in the bear case. The margin-of-safety price is $23.50, about 40% below the base case. That discount is wide because most of the portfolio is unpatented generics exposed to new competitors, two important products are already declining, a few wholesalers control most sales, and refinancing comes due in 2028 and 2029. The estimate would prove too high if erosion spreads across more of the generic lines or BAQSIMI loses ground to rivals; it would prove too low if the pipeline adds approved products faster than the older ones fade.