Zymeworks Inc. (ZYME) stock intrinsic value fair value estimate & owner earnings analysis

WHAT THE BUSINESS IS NOW. Zymeworks began as a Vancouver-founded antibody-drug developer and, until this month, earned money almost entirely from partners: Jazz Pharmaceuticals (which sells Ziihera, the HER2-targeted bispecific antibody Zymeworks invented), BeOne Medicines (Asia), Johnson & Johnson (pasritamig, now in two Phase 3 prostate cancer trials) and several platform partners. It has had no profitable year since at least 2020 other than 2022, when Jazz's $325 million upfront payment lifted revenue to $412 million; in 2023, 2024 and 2025 it spent roughly $200 million a year to bring in $76-106 million. On September 23, 2026 it closed the $929 million purchase of Theravance Biopharma, which adds a 35% share of US profits on YUPELRI (a nebulized COPD drug sold by Viatris; $75 million to Theravance in 2025 on $266.6 million of US sales) plus a $100 million TRELEGY-related milestone that Zymeworks expects in early 2027. On August 25, 2026 the FDA approved Ziihera for first-line HER2-positive gastroesophageal cancer, which triggered a $250 million milestone payment from Jazz. We value the company as it now stands, after those events. HOW WE MEASURED EARNINGS. Zymeworks's own history is not a usable earnings base: on our owner-earnings measure (operating cash flow less working-capital swings, stock compensation and maintenance capital spending) it produced about -$4.14, +$2.09, -$1.50, -$1.30 and -$0.91 per share for 2021 through 2025, and the one positive year is a one-time upfront payment. The company also changed shape in 2026 (new debt, Theravance, an approved second Ziihera indication), so no historical window describes it. We instead build value from the specific income streams that already exist, less the cash costs of running them. Trailing owner earnings improved about 30% in 2025 (from -$1.30 to -$0.91) because milestone revenue rose; we assume no such improvement carries into year one, and we start Ziihera royalties from the second-quarter 2026 run rate (about $1.8 million a quarter, roughly 12% of Jazz's $15.4 million of quarterly Ziihera sales). WHAT WE CREDITED AND WHAT WE LEFT OUT. Credited: (1) the YUPELRI profit share, about $75 million a year, flat, until generic makers are licensed to enter on April 23, 2039, then a fade to zero over about two years; (2) Ziihera royalties of 10% or more of sales, credited only until 2036 when regulatory exclusivity ends; (3) the $250 million GEA milestone, already earned; (4) the $100 million TRELEGY milestone; (5) the costs of running the business: about $40 million a year of corporate cost, $28 million of one-time integration cost, and a wind-down of the research already under way (about $80 million, $40 million, $20 million, then $10 million a year). Left out: any value from Zymeworks's own early-stage programs (ZW191, ZW251, the new multispecific programs) and platform partnerships beyond Ziihera and pasritamig, because none has reached a stage that we can point to for evidence of future income, and by the same logic we do not charge research spending beyond what is already committed; up to $190 million of further GEA approval milestones in Europe, Japan and China and $89 million for a third indication, which depend on approvals that have not happened; Viatris's $50 million and $75 million YUPELRI sales milestones (US sales are about half the first threshold); the contingent payment to Theravance holders on ampreloxetine; and the $2.5 billion of Irish tax losses that come with Theravance, though we do tax our income at 20%. WHAT THE BUSINESS OWES. Two non-recourse loans sit on the income streams. A $350 million OMERS note (8.25%, due 2036) is repaid from 75% of the YUPELRI profit share; at today's profit share it is repaid by about 2035, and because it costs more than 6% we count it at about $385 million. A $250 million Royalty Pharma loan taken in March 2026 is secured only by 30% of Ziihera royalties and is not owed by Zymeworks itself, so we count only the value of those royalties (about $43 million in the base case). The cash it raised is kept as cash. Theravance also brings an $85.7 million tax-uncertainty liability, which we count half in the base case and in full in the bear case. We estimate about $300 million of cash and investments today (June 30 balance of $322.5 million, plus the $250 million milestone, less about $218 million paid at closing, third-quarter spending and share repurchases); that estimate is ours, not a reported figure. BASE CASE ($0.81 per share). Business worth about $146 million after the costs above, plus $85 million from the TRELEGY milestone, plus $300 million of cash, less about $470 million owed (OMERS note $385 million, Royalty Pharma claim $43 million, tax liability $43 million): about $59 million, or $0.81 per share on about 72.5 million shares. Ziihera royalties grow to about $22 million a year by 2030 (sales of about $200 million, roughly triple today's run rate, on the newly approved gastroesophageal label and the 2.5-fold year-over-year growth seen in biliary tract cancer), stay there through 2036, and then fade. Even so, the income streams barely cover the cost of running the company, so the cash on hand is largely consumed by costs and debt service. BEAR CASE (-$1.57 per share). The generic maker Mankind Pharma has agreed not to enter before August 25, 2031, so YUPELRI profit falls back to its 2024 level of $64 million, halves in 2031 and falls to a quarter afterward; the OMERS note then absorbs 75% of the profit and is not repaid by 2036, leaving lenders with the asset. Ziihera royalties stall near $12 million a year. The full $89 million tax liability is paid. The business is worth about -$119 million before cash, the TRELEGY milestone adds $85 million and cash $300 million, and about $380 million is owed, leaving about -$114 million. In plain terms, in this case the company owes and spends more than its income streams are worth, and cash would run out around 2032 unless costs were cut or shares issued. BULL CASE ($8.39 per share). YUPELRI profit grows 5% a year for six years (below the 7% demand growth seen in 2025) to about $100 million; Ziihera sales reach about $500 million by 2031 (royalties about $60 million a year) as the gastroesophageal launch succeeds; the remaining $190 million of ex-US GEA approval milestones arrive in 2028-2029; pasritamig is approved around 2029 and earns Zymeworks about $30 million a year in royalties; and the tax liability lapses. That is a business worth about $710 million after costs and taxes, plus $85 million and $300 million of cash, less about $486 million owed, or about $608 million. WHAT COULD MAKE THIS WRONG. Costs are the biggest swing factor: every $10 million a year of ongoing corporate cost changes value by about $1.30 a share, and 2025 general and administrative spending was $61.5 million, well above our $40 million assumption, which relies on Theravance's smaller cost base and the wind-down of research. We could not confirm from filings the exact cash received from the GEA milestone, the combined company's cost plan, or the final closing balance sheet; these are drawn from company announcements and our estimates. Upside we exclude is real but unproven: further Ziihera indications (breast cancer trial data expected 2027-2028), pasritamig, the ex-US approvals and the platform partnerships that together carry billions of dollars of contractual milestones. If several of those succeed, value will be closer to the bull case.