AstraZeneca reported that SERENA-4 failed to show statistically significant benefit for Etcamah (camizestrant) as a first-line treatment in advanced ER-positive, HER2-negative breast cancer. The company said the regimen produced only a numerical progression-free survival improvement without meeting the primary endpoint. The disappointment follows AstraZeneca’s accelerated approval earlier in the month for Etcamah in a biomarker-driven setting where treatment is guided by ESR1 mutation detection. The setback also highlights how oral SERDs are still struggling to reproduce the magnitude of benefits seen in specific resistant subgroups. Investors will now look to AstraZeneca’s remaining confirmatory strategy, including other ongoing studies intended to expand Etcamah’s label across additional first-line or tumor-define segments.