HERIZON-GEA-01 Efficacy Results and the Role of HER2 Expression in the FDA Label

Dr. Kim reviews the primary results of HERIZON-GEA-01. Both zanidatamab-containing arms significantly improved progression-free survival vs trastuzumab plus chemotherapy, with a similar magnitude of benefit. The triplet of zanidatamab, tislelizumab, and chemotherapy produced a statistically significant overall survival benefit, reaching a median survival milestone not previously achieved in a large first-line trial in this setting. She adds that the doublet arm has since also shown a statistically significant overall survival benefit. Dr. Pereira places these findings in historical context, noting that the control arm outperformed historical expectations yet was still surpassed. The physicians then examine the recent FDA approval, which distinguishes the regimens by HER2 expression. The triplet is indicated across HER2-positive disease as defined by IHC and ISH testing, whereas the doublet is limited to tumors with the highest level of HER2 expression. Dr. Pereira notes he is inclined to offer the triplet across HER2-positive subgroups pending further data.