FDA Approves New Breast Cancer Treatment for Specific Genetic Mutation
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FDA Approves New Breast Cancer Treatment for Specific Genetic Mutation
- The U.S. Food and Drug Administration (FDA) has granted accelerated approval to camizestrant (Etcamah) in combination with a CDK4/6 inhibitor for adults with hormone receptor (HR)-positive, HER2-negative, locally advanced or metastatic breast cancer upon detection of an estrogen receptor-1 (ESR1) mutation.
- This approval, announced on September 4, 2026, marks the first time a cancer therapy has been approved based on the detection of a resistance mutation in circulating tumor DNA (ctDNA) before imaging tests show disease progression.
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On September 4, 2026, the U.S. Food and Drug Administration (FDA) gave accelerated approval to camizestrant (Etcamah), an oral selective estrogen receptor degrader (SERD), for certain patients with advanced breast cancer. This treatment, developed by AstraZeneca, is to be used in combination with a CDK4/6 inhibitor (such as abemaciclib, palbociclib, or ribociclib) for adult patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, locally advanced or metastatic breast cancer. The approval specifically targets cases where an estrogen receptor-1 (ESR1) mutation is detected during prior aromatase inhibitor and CDK4/6 inhibitor therapy, identified by an FDA-authorized test.
The FDA also approved the Guardant360 CDx assay as a companion diagnostic device to identify patients with these ESR1 mutations. This is a significant development as it represents the first FDA approval of a cancer therapy guided by the detection of a resistance mutation in circulating tumor DNA (ctDNA) before traditional imaging shows disease progression. Acting FDA Commissioner Kyle Diamantas, J.D., noted that this approval provides a targeted therapy designed to overcome resistance in patients whose tumors continuously evolve.
The accelerated approval was based on efficacy data from the Phase III SERENA-6 trial, which involved 315 patients. In this trial, patients whose ESR1 mutation was detected via a blood test while on standard first-line treatment, but without evidence of disease progression, were randomized to either switch to camizestrant with a CDK4/6 inhibitor or continue their original aromatase inhibitor and CDK4/6 inhibitor therapy. Patients who switched to camizestrant achieved a median progression-free survival (PFS) of 16 months, compared to 9.2 months for those who continued their original treatment, demonstrating a 56% reduction in the risk of progression or death.
Despite an earlier advisory panel vote against the medicine in April 2026, the FDA granted accelerated approval. The FDA subsequently requested additional evidence, including ctDNA clearance data linked to longer-term outcomes. Continued approval for this indication may be contingent upon verification of clinical benefit in confirmatory trials. The prescribing information for camizestrant includes a boxed warning regarding the risk of irregular heart rhythm when taken with certain other medications, as well as warnings for an abnormally slow heart rate and potential harm to an unborn baby.