ZYME Surges 41.41% to Monthly High on Positive Phase 3 Trial Results for Ziihera

The share price rose to its highest level so far this month today, with an intraday gain of 41.41%.

Zymeworks Inc. (ZYME) surged on the back of positive Phase 3 clinical trial results for its bispecific HER2-targeted antibody Ziihera (zanidatamab) in treating HER2-positive gastroesophageal adenocarcinoma. The HERIZON-GEA trial demonstrated statistically significant improvements in progression-free survival for Ziihera combined with chemotherapy versus the current standard of care. A triple combination with BeOne’s PD-1 antibody Tevimbra further boosted overall survival, reinforcing the drug’s therapeutic potential. Jazz Pharmaceuticals, which holds commercialization rights in key markets, plans to submit a supplemental Biologics License Application in early 2026 to expand Ziihera’s approval to first-line treatment, targeting a $700 million market.

The trial results have elevated investor optimism, with Zymeworks positioned to benefit from tiered royalties on global sales. Partners Jazz and BeOne project combined peak annual sales exceeding $2.3 billion by the 2030s, translating to potential royalty revenue of $340 million or more for Zymeworks. The company’s collaboration model, which offloads commercialization and regulatory risks to partners, allows it to focus on R&D while capturing value through milestone payments and scalable royalties. With $251.9 million in cash as of Q3 2025 and a projected runway through mid-2027, Zymeworks is well-positioned to fund ongoing trials and capitalize on long-term growth, though regulatory and competitive uncertainties remain.