Core Insights - Zymeworks Inc. stock is experiencing a significant surge following the announcement of positive topline results from the Phase 3 HERIZON-GEA-01 trial for Ziihera in combination with chemotherapy [1][7] Group 1: Trial Results - The Phase 3 trial evaluated Ziihera (zanidatamab-hrii) as a first-line treatment for HER2-positive locally advanced or metastatic gastroesophageal adenocarcinoma, showing statistically significant improvements in progression-free survival (PFS) compared to the control arm [2] - Ziihera plus Tevimbra and chemotherapy demonstrated clinically meaningful and statistically significant improvements in overall survival (OS) [3] - A strong trend toward statistical significance in OS was observed for Ziihera plus chemotherapy compared to the control arm, with an additional OS interim analysis planned for mid-2026 [4] Group 2: Efficacy and Subgroup Analysis - Benefits in PFS and OS were noted in both PD-L1-positive and PD-L1-negative subgroups for the Ziihera plus Tevimbra and chemotherapy arm versus the control arm [5] - Improvements in key secondary endpoints, including objective response rate (ORR) and duration of response (DoR), were supportive of the primary efficacy endpoints [5] Group 3: Future Plans and Regulatory Actions - Jazz Pharmaceuticals plans to present the trial data at a major medical meeting in Q1 2026 and aims for publication in a peer-reviewed journal, along with rapid adoption in the National Comprehensive Cancer Network Guidelines [6] - A supplemental Biologics License Application is expected to be submitted in the first half of 2026 to support Ziihera as a first-line treatment for HER2+ locally advanced or metastatic GEA [6] Group 4: Market Reaction - Following the announcement, Zymeworks stock rose by 36.20% to $25.23, while Jazz Pharmaceuticals and BeOne Medicines also saw significant stock price increases of 20.45% and 3.37%, respectively [7]