FDA Approval

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

Edited by:
Anthony Calabro, MA

Key Highlights

  • Camizestrant is approved with abemaciclib, palbociclib, or ribociclib.
  • Treatment requires detection of an ESR1 mutation with an FDA-authorized test.
  • Estimated median progression-free survival was 16 months with camizestrant versus 9.2 months with continued aromatase inhibitor therapy.
  • Confirmatory studies must verify and describe clinical benefit.

On September 4, the FDA granted accelerated approval to camizestrant (Etcamah, AstraZeneca) combined with a CDK4/6 inhibitor—abemaciclib, palbociclib, or ribociclib—for adults with hormone receptor (HR)–positive, HER2-negative, locally advanced or metastatic breast cancer. Treatment is indicated when an ESR1 mutation is detected with an FDA-authorized test during aromatase inhibitor and CDK4/6 inhibitor therapy.

ESR1 mutations are acquired resistance mutations that may develop while a patient is receiving an aromatase inhibitor, a common front-line endocrine treatment for locally advanced or metastatic breast cancer. Fewer than 5% of patients have an ESR1 mutation when HR-positive metastatic breast cancer is diagnosed. After disease progression during aromatase inhibitor therapy, nearly 40% have the mutation. The FDA also authorized Guardant360 CDx as a companion diagnostic for identifying eligible patients.

Efficacy was evaluated in a clinical trial comparing a switch to oral camizestrant plus a CDK4/6 inhibitor with continued aromatase inhibitor plus CDK4/6 inhibitor therapy. Estimated median progression-free survival, measured from detection of the resistance mutation in blood, was 16 months in the camizestrant group and 9.2 months in the comparator group. Because clinical benefit from intervention before imaging-confirmed progression remains unconfirmed, the FDA required confirmatory studies.

“This marks the first FDA approval of a cancer therapy guided by the detection of a resistance mutation in circulating tumor DNA,” Angelo de Claro, MD, director of the FDA Oncology Center of Excellence, said in a press release.

Prescribing information includes a boxed warning concerning irregular heart rhythm when camizestrant is combined with certain medications. Warnings and precautions also address an abnormally slow heart rate and potential fetal harm.

Reference
US Food and Drug Administration. FDA grants accelerated approval to a new breast cancer treatment. Published September 4, 2026. Accessed September 15, 2026. https://www.fda.gov/news-events/press-announcements/fda-grants-accelerated-approval-new-breast-cancer-treatment