The U.S. Food and Drug Administration (FDA) has granted accelerated approval to AstraZeneca’s Etcamah (camizestrant) for certain adults with advanced breast cancer, expanding treatment options for patients whose tumors develop a specific resistance mutation.
Etcamah is approved in combination with a CDK4/6 inhibitor, including abemaciclib, palbociclib or ribociclib. It is intended for adults with hormone receptor (HR)-positive, HER2-negative, locally advanced or metastatic breast cancer whose tumors develop an ESR1 mutation while being treated with an aromatase inhibitor and a CDK4/6 inhibitor.
ESR1 mutations are acquired changes that can allow breast cancer cells to become resistant to aromatase inhibitors, a commonly used type of hormone therapy. While fewer than 5% of patients have an ESR1 mutation when metastatic breast cancer is first diagnosed, the mutation can be found in nearly 40% of patients after their disease progresses on an aromatase inhibitor.
The FDA’s decision is notable because treatment with Etcamah can begin when the ESR1 mutation is detected through a blood test, before imaging confirms that the cancer has progressed.
“Women living with metastatic breast cancer face an uphill battle as their tumors continuously evolve to escape treatment,” said Acting FDA Commissioner Kyle Diamantas, J.D. He said the approval provides patients with a targeted treatment designed to address treatment resistance.
The accelerated approval was based on progression-free survival, which measures how long patients live without their disease worsening. In the clinical trial, patients who received Etcamah with a CDK4/6 inhibitor had an estimated median progression-free survival of 16 months, compared with 9.2 months for patients who continued treatment with an aromatase inhibitor and a CDK4/6 inhibitor.
However, the FDA said additional studies are needed to confirm whether starting treatment at the time an ESR1 mutation is detected, rather than waiting for confirmed disease progression, provides a meaningful clinical benefit. Confirmatory studies will therefore be required as part of the accelerated approval.
Angelo de Claro, M.D., director of the FDA’s Oncology Center of Excellence, said the decision marks the first FDA approval of a cancer therapy guided by the detection of a resistance mutation in circulating tumor DNA (ctDNA) before imaging shows disease progression.
ctDNA consists of small pieces of DNA released by tumors into the bloodstream. Testing this DNA can help identify certain cancer-related genetic changes earlier than conventional imaging.
Alongside the drug approval, the FDA authorized the Guardant360 CDx assay as a companion diagnostic. The test is designed to identify breast cancer patients with ESR1 mutations who may be eligible for camizestrant treatment.
Etcamah’s prescribing information includes a boxed warning about the risk of irregular heart rhythms when the drug is used with certain other medicines. It also contains warnings about abnormally slow heart rate and the potential risk of harm to an unborn baby.
The FDA previously convened its Oncologic Drugs Advisory Committee on April 30, 2026, to review the application.
The accelerated approval was granted to AstraZeneca and represents a new approach to using blood-based molecular testing to guide treatment decisions in advanced breast cancer.