FDA Grants Accelerated Approval to Camizestrant for ESR1-Mutated Advanced Breast Cancer

The FDA granted accelerated approval to Etcamah (camizestrant) with abemaciclib, palbociclib, or ribociclib for adults with HR-positive, HER2-negative locally advanced or metastatic breast cancer upon detection of an ESR1 mutation during aromatase inhibitor and CDK4/6 inhibitor therapy. Detection must use an FDA-authorized test. The agency also authorized Guardant360 CDx as a companion diagnostic.

The supporting clinical trial evaluated switching the aromatase inhibitor to oral camizestrant while maintaining CDK4/6 inhibition, versus continuing the aromatase inhibitor combination. Estimated median progression-free survival was 16 months with camizestrant versus 9.2 months with continued aromatase inhibitor therapy, measured from detection of the resistance mutation in blood. The announcement did not report sample size or statistical uncertainty.

According to the FDA, this is its first cancer therapy approval guided by detection of a resistance mutation in circulating tumor DNA before imaging shows progression. However, whether switching at molecular detection rather than confirmed disease progression provides clinically meaningful benefit remains unconfirmed. The agency requires confirmatory studies to verify and describe clinical benefit.

Prescribing information includes a boxed warning about irregular heart rhythm when camizestrant is taken with certain other medications, plus warnings for abnormally slow heart rate and potential fetal harm. The accelerated approval was granted to AstraZeneca.