The U.S. Food and Drug Administration granted accelerated approval to AstraZeneca's Etcamah (camizestrant) in combination with a CDK4/6 inhibitor for adult patients with hormone receptor-positive, HER2-negative, locally advanced or metastatic breast cancer who develop an estrogen receptor-1 (ESR1) mutation during treatment.

According to a statement from the FDA, the approval is based on detection of the ESR1 resistance mutation using an authorized test. ESR1 mutations occur in fewer than 5% of patients at the time of initial HR-positive metastatic breast cancer diagnosis but are present in nearly 40% of patients after disease progression on an aromatase inhibitor.

The FDA described the approval as the first for a cancer therapy guided by the detection of a resistance mutation in circulating tumor DNA (ctDNA) before imaging confirms disease progression. Angelo de Claro, M.D., director of the FDA's Oncology Center of Excellence, noted that "additional evidence is needed to confirm clinical benefit," as is standard under the accelerated approval pathway.

In a clinical trial, estimated median progression-free survival was 16 months in the Etcamah plus CDK4/6 inhibitor group, compared with 9.2 months in the aromatase inhibitor plus CDK4/6 inhibitor group.

The FDA also authorized the Guardant360 CDx assay as a companion diagnostic to identify eligible patients.

Etcamah's prescribing information includes a boxed warning for irregular heart rhythm when taken with certain medications, as well as warnings for abnormally slow heart rate and potential fetal harm. Confirmatory studies have been required to verify clinical benefit.

The FDA's Oncologic Drugs Advisory Committee met on April 30, 2026, to review the application.