BIOMARIN PHARMACEUTICAL INC (BMRN) stock intrinsic value fair value estimate & owner earnings analysis

BioMarin is a rare-disease biotechnology company built around a portfolio of enzyme-replacement therapies and one large, faster-growing drug, VOXZOGO, which treats achondroplasia (the most common form of dwarfism) in children. VOXZOGO now accounts for roughly 29% of revenue and has been the company's primary growth engine since its 2021 launch. Five older enzyme-replacement therapies -- Vimizim, Naglazyme, Palynziq, Aldurazyme and Brineura -- make up the stable core of the business; two of them (Naglazyme and Aldurazyme) are already off patent yet have never faced a generic or biosimilar competitor, because the patient populations are too small to attract one. A legacy drug, Kuvan, has been declining for years due to generic competition, and BioMarin recently discontinued Roctavian, a gene therapy that never gained commercial traction; both are minor to the total picture going forward. We valued BioMarin on its owner earnings -- cash generated by the business after real operating costs, stock-based compensation, and the capital spending needed just to maintain (not grow) the current business. On that basis, BioMarin has gone from consistently burning cash between 2016 and 2022 to generating a median of roughly $2.65 per share in the most recent three years, which we use as the starting point (anchor) for the valuation, rather than the most recent year alone, which was flattered by one-time items discussed below. Two accounting judgments matter here. First, in 2025 BioMarin acquired Inozyme Pharma and then wrote off $221 million of the value of that deal as a non-cash charge within the same year, on top of separate impairment and inventory write-off charges tied to the discontinued Roctavian product. These are real, one-time uses of shareholder money even though the write-offs themselves are non-cash, so while we add them back when measuring underlying cash generation (as is standard), we treat the pattern itself -- paying for assets and then writing them down almost immediately -- as a risk factor in our more cautious case rather than a reason to lower the reported cash-generation figure. Second, VOXZOGO's core U.S. and European patents expire in 2030, and BioMarin is currently in patent litigation against a competitor, Ascendis Pharma, over a rival drug for the same condition. Because VOXZOGO's growth cannot be assumed to continue indefinitely once that patent protection lapses, our long-term outlook assumes its growth slows and partially reverses in the years following 2030, while the older, patent-expired-but-uncontested therapies continue at a slow, steady pace. In our base case, VOXZOGO keeps growing at a solid but decelerating pace over the next five years (helped by an expanded pediatric label and international rollout already underway), overall owner earnings grow at roughly 10% next year -- well below the unusually strong growth of the past year -- and taper further as the 2030 patent cliff approaches, before settling into a flat, sustainable level supported mainly by the durable older drug franchise. That produces a value of roughly $64 per share. Our more cautious case assumes BioMarin's pending, debt-financed acquisition of Amicus Therapeutics (announced in December 2025, expected to close in 2026) adds meaningful leverage just as VOXZOGO's growth stalls and a rival treatment reaches the market sooner than expected, while further write-downs occur in the newly acquired pipeline -- a repeat of the pattern seen with Inozyme. Owner earnings decline for several years before stabilizing at a lower base, valuing the shares at roughly $32. Our more optimistic case assumes VOXZOGO's label expansion and international launches keep growth strong for longer, the Ascendis competitive threat proves less damaging than feared, and the Amicus integration goes smoothly without further write-downs. That case is worth roughly $101 per share. In this case, more than half of the total value depends on what BioMarin's businesses can sustainably earn many years from now, so it is more sensitive to how the VOXZOGO patent situation ultimately resolves than the other cases. Putting these together, the margin-of-safety price is meaningfully below our base-case estimate -- around $42 -- given the real uncertainty around the VOXZOGO patent expiration, the Ascendis litigation, and the execution risk in a large pending acquisition on top of a recent pattern of costly, quickly-reversed deals. We were not able to independently verify the exact revenue contribution BioMarin expects from the Amicus acquisition once it closes, since it has not yet occurred; our valuation reflects BioMarin's existing business only.