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News
The FDA has approved two new treatment options for ESR1-mutated, hormone receptor-positive, HER2-negative advanced breast cancer within weeks of each other. Imlunestrant plus abemaciclib (Lilly) received full approval for use after disease progression, while camizestrant plus a CDK4/6 inhibitor (AstraZeneca) got accelerated approval for use at the time of ESR1 mutation detection — before progression. Both regimens swap out the aromatase inhibitor for an oral SERD, but the timing differs significantly.
The FDA has approved two distinct treatment strategies for patients with ESR1-mutated, ER-positive, HER2-negative advanced or metastatic breast cancer — and they arrived just weeks apart. Imlunestrant (Inluriyo, Lilly) plus abemaciclib (Verzenio) received full FDA approval for adults whose disease has progressed after at least one line of endocrine therapy. Shortly before, camizestrant (Etcamah, AstraZeneca) plus a CDK4/6 inhibitor received accelerated approval for use at the point of ESR1 mutation detection — even before radiographic progression — marking the first time the FDA has approved a cancer treatment switch based on ctDNA testing rather than imaging.
The key distinction: Lilly's regimen is used after clinical progression, while AstraZeneca's enables an earlier switch once the ESR1 resistance mutation is detected during ongoing aromatase inhibitor therapy. Both use the Guardant360 CDx assay as a companion diagnostic.
By the Numbers
Why it matters: ESR1 mutations are a leading driver of endocrine resistance in advanced breast cancer. Having two approved SERD-based strategies — one for early intervention and one post-progression — gives oncologists more flexibility to tailor treatment timing to individual patients, potentially improving outcomes across a broader population.
