AstraZeneca reported that camizestrant (Etcamah) did not meet the primary endpoint in the Phase 3 Serena-4 trial, testing the oral selective estrogen receptor degrader (SERD) in first-line HER2-negative, ER-positive breast cancer. The company said the treatment produced only a numerical improvement in progression-free survival that failed to reach statistical significance. The negative result further constrains label ambitions for oral SERDs beyond the subgroup of patients with ESR1 mutations, where prior data have suggested clearer benefit. AstraZeneca has already leaned on an accelerated approval framework in a settings tied to ESR1 status. The development underscores how oral endocrine strategies remain highly sensitive to patient selection and trial design as companies aim to compete with existing standards and newer oral degraders.