Ziihera (zanidatamab-hrii), partnered to Jazz, approved on August 25, 2026 for first-line HER2-positive advanced gastro-oesophageal adenocarcinoma - triggering a $250 million milestone to Zymeworks.
Run-up into the decision (T-120 → T+5)
Daily close, T-120 (2/18/26) through T+0. Run-up high $28.56 on 4/27/26, low $21.81 on 8/3/26 (T-120 to T-1). FDA decision 8/25/26. Historical price action, not a forecast.
Key facts
FDA decision date2026-08-25
OutcomeApproved
Drug / candidateZiihera (zanidatamab-hrii)
IndicationFirst-line HER2-positive unresectable locally advanced or metastatic gastric, gastro-oesophageal junction and gastro-oesophageal adenocarcinoma (partnered with Jazz Pharmaceuticals)
CompanyZymeworks Inc.
Market-cap tierSmall
120-day run-up (T-120→T-1)+5.5%
Cohort decision-day move (history)3.6% median (n=279)
The PDUFA target action date was August 25, 2026 and the FDA approved the supplemental BLA that day. Zanidatamab originated at Zymeworks and is partnered to Jazz Pharmaceuticals, which holds the US application; this listing exists because the approval is material to Zymeworks, which is entitled to a $250 million milestone payment on it. The approval covers all HER2-positive patients (IHC 3+ and IHC 2+/ISH+) regardless of PD-L1 status, based on the Phase 3 HERIZON-GEA-01 trial: median progression-free survival of 12.4 months against 8.1 months for trastuzumab plus chemotherapy, a 35% reduction in the risk of progression or death.
Run-up figures are the stock's own daily closing path over the 120 trading days before the decision, from our price history. Cohort move is the historical median absolute decision-day move for this market-cap tier. History, not a prediction.
Was Ziihera (zanidatamab-hrii) approved by the FDA?
Yes. The FDA approved the application for Ziihera (zanidatamab-hrii) on August 25, 2026. The primary source is linked on this page.
Which company is behind Ziihera (zanidatamab-hrii)?
Ziihera (zanidatamab-hrii) is a Zymeworks Inc. (ZYME) program. The FDA decision came on August 25, 2026; the company's own announcement is linked on this page.
How did ZYME stock trade into the FDA decision?
Measured over the 120 trading days before the decision (T-120 to T-1), ZYME moved +5.5%. That is the recorded price path into this specific event -- historical measurement, not a prediction, and not investment advice.
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