The FDA granted accelerated approval to AstraZeneca’s oral SERD camizestrant (Etcamah/camizestrant), overturning a prior advisory committee vote that had gone against the drug for first-line breast cancer. The decision covers patients with HR+/HER2- advanced breast cancer harboring ESR1 mutations detected during aromatase inhibitor and CDK4/6 inhibitor therapy. The approval also comes alongside Guardant Health’s Guardant360 companion diagnostic to identify ESR1 mutations. In SERENA-6, the company reported progression-free survival results meeting the primary endpoint, while the earlier panel raised concerns about the design and the randomized treatment switch based on mutation detection timing. Biotech implications are immediate for SERD developers and companion diagnostic strategies: the FDA’s approval effectively validates ESR1 mutation testing earlier in the treatment course and keeps a competitive oral SERD option in play for HR+/HER2- settings. It also increases the importance of evidence design around switch criteria and maturity of overall survival data.