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NewsThe FDA approved two new combination regimens for ESR1-mutated, HR+/HER2- advanced breast cancer within weeks of each other. Imlunestrant plus abemaciclib targets patients after disease progression, while camizestrant plus a CDK4/6 inhibitor intervenes earlier — at mutation detection, before progression. Both approvals rely on the Guardant360 CDx assay to identify eligible patients.
The FDA approved two new treatment combinations for ESR1-mutated, hormone receptor-positive (HR+), HER2-negative advanced or metastatic breast cancer in rapid succession, giving oncologists a pair of new tools — with a key strategic difference in timing.
Imlunestrant + abemaciclib (Inluriyo + Verzenio, Eli Lilly) received full approval on September 18 for patients who have progressed on at least one line of endocrine therapy. Based on the phase 3 EMBER-3 trial, the combination nearly halved the risk of progression compared to imlunestrant alone in ESR1-mutated patients. Camizestrant + CDK4/6 inhibitor (Etcamah, AstraZeneca) received accelerated approval on September 4 for patients whose ESR1 mutation is detected before radiographic progression — marking the first time the FDA has approved a cancer treatment switch based on ctDNA testing alone, rather than imaging-confirmed disease progression.
By the Numbers:
Why it matters: ESR1 mutations are a leading driver of endocrine therapy resistance in advanced breast cancer. These two approvals expand the treatment toolkit at different points in the disease course — and open a broader clinical conversation about whether to act at mutation detection or wait for disease progression.
