FDA approves AZ’s Etcamah for pre-progression switch in HR+ breast cancer

AstraZeneca has received accelerated approval from the US FDA for Etcamah (camizestrant), an oral selective estrogen receptor degrader (SERD), in combination with a CDK4/6 inhibitor for adult patients with hormone receptor (HR)-positive, HER2-negative locally advanced or metastatic breast cancer who develop an ESR1 mutation during first-line aromatase inhibitor (AI) and CDK4/6 inhibitor therapy. The approval is contingent on detection using an FDA-authorized companion diagnostic test and marks a pre-progression, circulating tumor DNA (ctDNA)-guided therapy switch.

Etcamah is administered orally once daily at 75 mg in combination with any of three approved CDK4/6 inhibitors — abemaciclib, palbociclib, or ribociclib. The companion diagnostic, approved concurrently, detects emergent ESR1 mutations in ctDNA from blood samples collected every two to three months during routine monitoring, enabling a therapy switch before radiographic or clinical disease progression occurs.

The approval is based on the Phase III SERENA-6 trial, which enrolled 315 patients with HR-positive, HER2-negative advanced breast cancer harboring emergent ESR1 mutations during first-line AI plus CDK4/6 inhibitor therapy. In a planned interim analysis, Etcamah combined with a CDK4/6 inhibitor reduced the risk of disease progression or death by 56% versus continued AI plus CDK4/6 inhibitor (hazard ratio 0.44; 95% CI: 0.31–0.60; p<0.00001; median progression-free survival 16.0 versus 9.2 months). A subsequent pre-planned analysis reported a statistically significant progression-free survival 2 benefit of 25.7 versus 19.1 months (HR: 0.63; p=0.00373); overall survival data remain immature.

Camizestrant binds estrogen receptor alpha (ERα) with high affinity — including ESR1-mutant forms that confer ligand-independent activation and resistance to AIs — inducing receptor degradation while providing complete antagonism. Its oral bioavailability differentiates it from fulvestrant, a first-generation SERD requiring intramuscular injection. The ctDNA-guided switch strategy exploits the approximately 30% rate of emergent ESR1 mutations in first-line HR-positive patients prior to clinical progression, as cited by AstraZeneca.

Etcamah enters an increasingly crowded estrogen receptor degrader market but occupies a distinct clinical niche. Elacestrant (Orserdu) and Lilly’s imlunestrant (Inluriyo) are approved for ESR1-mutated advanced or metastatic disease after progression on prior endocrine therapy, while Arvinas and Pfizer’s vepdegestrant (Veppanu), a PROTAC ER degrader, received a similar post-progression approval in May 2026. Etcamah is differentiated by its pre-progression label, allowing treatment to switch upon ctDNA detection of an emergent ESR1 mutation before radiographic progression. Roche’s giredestrant is under FDA review in post-CDK4/6 ESR1-mutated advanced disease based on the positive Phase III evERA study, although the drug separately missed the primary endpoint in the first-line Phase III persevERA trial.

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