FDA Grants Accelerated Approval to Etcamah for ESR1-Mutated Breast Cancer

The FDA granted accelerated approval to camizestrant (Etcamah, AstraZeneca) in combination with a CDK4/6 inhibitor for adults with hormone receptor-positive, human epidermal growth factor receptor 2-negative locally advanced or metastatic breast cancer whose tumors develop an ESR1 mutation during treatment with an aromatase inhibitor and a CDK4/6 inhibitor.

The agency said eligibility depends on detection of the ESR1 mutation with an FDA-authorized test. The approved CDK4/6 partners are abemaciclib, palbociclib, or ribociclib. FDA characterized ESR1 mutations as acquired resistance mutations that may emerge during aromatase inhibitor therapy.

In the evidence cited by FDA, estimated median progression-free survival was 16 months with camizestrant plus a CDK4/6 inhibitor and 9.2 months with an aromatase inhibitor plus a CDK4/6 inhibitor. The approval permits treatment to change when the mutation is detected, rather than waiting for confirmed disease progression.

The camizestrant labeling carries a boxed warning about irregular heart rhythm when the drug is used with certain medications. Warnings and precautions also address bradycardia and potential fetal harm. FDA did not report a confirmed clinical benefit for switching therapy at molecular progression in the announcement.

Because the action used the accelerated approval pathway, FDA required confirmatory studies to verify and describe clinical benefit. The agency emphasized that additional evidence is needed to determine whether intervention at ESR1 mutation detection produces a meaningful benefit compared with changing treatment after clinical progression.

Source: US Food and Drug Administration. FDA grants accelerated approval to a new breast cancer treatment. Press announcement. US Food and Drug Administration; September 4, 2026. Accessed September 6, 2026.