The Food and Drug Administration on September 4, 2026 granted accelerated approval to Etcamah (camizestrant) in combination with a CDK4/6 inhibitor for adults with hormone-receptor-positive, HER2-negative locally advanced or metastatic breast cancer whose tumors develop an ESR1 mutation during aromatase-inhibitor and CDK4/6-inhibitor therapy, based on an FDA-authorized test. According to the FDA drug-approval notice, this is the first FDA approval of a cancer therapy guided by the detection of a resistance mutation in circulating tumor DNA before imaging shows that the disease is progressing.
Etcamah is a next-generation oral selective estrogen receptor degrader developed by AstraZeneca. It is administered orally in combination with abemaciclib, palbociclib, or ribociclib. Alongside the drug approval, the FDA authorized the Guardant360 CDx assay as a companion diagnostic to identify patients with breast cancer whose tumors carry an ESR1 mutation and are candidates for treatment with camizestrant.
According to the FDA notice, ESR1 mutations are acquired resistance mutations that a tumor can develop during treatment with an aromatase inhibitor — a common front-line hormone-directed therapy for advanced HR-positive breast cancer. Fewer than 5 percent of patients have an ESR1 mutation at the time of an HR-positive metastatic breast cancer diagnosis; after disease progression on an aromatase inhibitor, nearly 40 percent of patients will carry the mutation, the FDA notice states.
Efficacy was evaluated in SERENA-6 (NCT04964934), a randomized, double-blind, placebo-controlled, multicenter trial. According to the FDA drug-approval notice, 315 patients with ER-positive, HER2-negative locally advanced or metastatic breast cancer and detectable ESR1 mutations were randomized 1:1 to switch to camizestrant plus a CDK4/6 inhibitor or to continue an aromatase inhibitor (anastrozole or letrozole) plus a CDK4/6 inhibitor. Median progression-free survival was 16 months in the camizestrant arm and 9.2 months in the aromatase-inhibitor arm (hazard ratio 0.44; p-value less than 0.00001). Overall-survival data were not mature at the time of the analysis. According to the AstraZeneca press release, the SERENA-6 results were first presented at the 2025 American Society of Clinical Oncology Annual Meeting and simultaneously published in The New England Journal of Medicine.
The prescribing information includes a boxed warning for the risk of arrhythmia due to QTc-interval prolongation when Etcamah is used with other QTc-prolonging drugs, as well as warnings and precautions for bradycardia and embryo-fetal toxicity, according to the FDA drug-approval notice.
