PUMA BIOTECHNOLOGY, INC. (PBYI) stock intrinsic value fair value estimate & owner earnings analysis

Puma Biotechnology sells one drug, NERLYNX (neratinib), an oral treatment for HER2-positive breast cancer. About 90% of revenue is U.S. product sales ($204M in 2025); the rest is royalties from partners selling abroad, mostly in China ($24M in 2025, down from $35M in 2024). Revenue has been flat for three years ($236M, $230M, $228M) and the first half of 2026 was about 3% higher than a year earlier. What the business earns. We measure earnings as operating cash flow, less swings in receivables and accruals, less stock compensation (a real cost, treated as such), less the very small equipment spending. That gives about $0.73 per share in 2023, $0.70 in 2024 and $0.89 in 2025. Earlier years (2020 to 2022) were dominated by stock compensation of $12M to $37M a year and a 2022 restructuring, so they describe a different company and are not used. We anchor on the 2023 to 2025 middle value, about $0.70 to $0.73 per share. The 2025 figure rose 27%, but much of that came from working-capital timing and lower interest costs as debt was repaid, so we do not extrapolate it; we assume no growth in year one. Amortization of about $11M a year on purchased rights to the drug is added back as a sunk cost, and its economic decay is reflected instead in the drug's finite life below. The defining fact is a dated end point. Puma settled its patent case with Sandoz in 2022, allowing a generic NERLYNX in the U.S. on or around December 8, 2030. The company's key composition patent (extended) also expires December 2030. Nothing in the filings names a replacement product that is approved or under contract, so the value of the business is the cash it can earn from NERLYNX until then, plus a short tail. Base case: earnings of about $0.70 per share a year through 2030, reflecting flat U.S. sales and continued shrinkage of Chinese royalties, then generic competition cuts earnings to roughly half in 2031, about a tenth in 2032, and nothing after. Value: about $3.25 per share. Bear case: royalty erosion continues (it already fell 31% in 2025) and U.S. net pricing keeps slipping from government chargebacks and payer mix, taking earnings to about $0.45 in 2026 and down roughly 10% a year to $0.30 in 2030, then a sharp generic drop. Value: about $1.65. Bull case: the 2025 level of about $0.90 per share is sustained to 2030 (supported by the demonstrated cost cuts, with selling and administrative expense down from about $89M to $71M since 2023), with a slower generic decline afterwards. Value: about $4.40. What we left out. We give no credit for the alisertib development program or any new product, since none has an approval or contract. Cash and securities (about $98M at year-end 2025 against about $23M of remaining debt) are not added separately because our earnings measure already reflects interest costs; readers who value that net cash separately would see a higher figure. The $22.5M of remaining debt falls due in 2026 and is small relative to annual earnings. What would make this wrong: a court or regulator moving generic entry earlier than 2030, faster erosion of U.S. sales than the flat three-year record, or a successful new product or extended protection that we have not credited. The margin-of-safety price of $2.00 sits well below the base case because the stream has a hard end date, a single product, and a bear case near half of base.