Zymeworks' Phase 3 Trial Shows Significant Improvements

By Tamara Parker • Monday, November 17 15:38 • Permanent Link

Zymeworks Inc. has recently released positive topline results from its phase 3 Herizon-GEA-01 trial evaluating ZW25 (zanidatamab-hir2) in combination with chemotherapy, with or without the PD-1 inhibitor tevimbra (tislelizumab). The trial was conducted as a first-line treatment for HER2-positive (HER2+) locally advanced or metastatic gastroesophageal adenocarcinoma, including cancers of the stomach, gastroesophageal junction, and esophagus. The results indicate significant improvements when compared to the control arm, trastuzumab plus chemotherapy.

The key findings from the Herizon-GEA-01 trial are as follows: Both ZW25 plus chemotherapy and ZW25 plus tevimbra and chemotherapy demonstrated highly statistically significant and clinically meaningful improvements in progression-free survival (PFS) compared to the control arm. ZW25 plus tevimbra and chemotherapy also showed clinically meaningful and statistically significant improvements in overall survival (OS), and ZW25 plus chemotherapy demonstrated a clinically meaningful effect with a strong trend toward statistical significance for OS. * A PFS and OS benefit was observed in the ZW25 plus tevimbra and chemotherapy arm versus the control arm in both PD-L1 positive and PD-L1 negative subgroups.

Furthermore, both ZW25 plus tevimbra and chemotherapy, and ZW25 plus chemotherapy demonstrated improvements in the key secondary endpoints of objective response rate (ORR) and duration of response (DOR) versus the control arm, supporting the primary efficacy endpoints.

The safety profile of ZW25 in combination with chemotherapy, with or without tevimbra, was generally consistent with the known safety profile of each agent, with no new safety signals observed in the investigational combination arms, supporting the overall benefit-risk of ZW25 for use in this indication.

Following these positive results, Jazz Pharmaceuticals, Zymeworks' partner, intends to submit a supplemental biologics license application in the first half of 2026 to support ZW25 as a first-line treatment for patients with HER2+ locally advanced or metastatic gastroesophageal adenocarcinoma for use as part of a standard chemotherapy regimen with or without tevimbra.

Today the company's shares have moved 31.38% to a price of $24.331. Check out the company's full 8-K submission here.

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