The Food and Drug Administration granted accelerated approval on September 4 to camizestrant, sold as Etcamah, a new AstraZeneca pill for a subset of patients with advanced breast cancer whose tumors have developed a specific drug-resistance mutation.
The approval covers adults with hormone receptor-positive, HER2-negative locally advanced or metastatic breast cancer who develop an ESR1 mutation while on treatment with an aromatase inhibitor and a CDK4/6 inhibitor. Camizestrant is meant to be taken in combination with one of three CDK4/6 inhibitors: abemaciclib, palbociclib or ribociclib.
ESR1 mutations are acquired resistance mutations that can emerge after a tumor has been exposed to an aromatase inhibitor, a common front-line hormone therapy for metastatic breast cancer. Fewer than 5% of patients have the mutation at initial diagnosis, but nearly 40% develop it after their disease progresses on an aromatase inhibitor, making it a frequent reason frontline therapy stops working.
The approval was supported by the SERENA-6 trial, a randomized, double-blind, placebo-controlled study that compared switching patients to camizestrant plus a CDK4/6 inhibitor against continuing an aromatase inhibitor plus a CDK4/6 inhibitor once an ESR1 mutation was detected. Median progression-free survival was about 16 months in the camizestrant arm, compared with 9.2 months for patients who stayed on the aromatase inhibitor combination.
The FDA also approved the Guardant360 CDx blood test as a companion diagnostic to identify which patients carry an ESR1 mutation and are eligible for the new combination. The recommended dose of camizestrant is 75 milligrams taken orally once a day, with or without food, continued until disease progresses or side effects become intolerable.
The approval gives oncologists a way to detect resistance to hormone therapy through a blood test and switch treatment before a scan shows the cancer has visibly worsened, rather than waiting for imaging to confirm progression.
The approval was not unanimous within the FDA itself. The agency’s Oncologic Drugs Advisory Committee voted 6-3 against recommending approval in April 2026, with dissenting members citing concerns about switching therapy based on a blood-test mutation before a scan shows the cancer has worsened. The FDA overruled its own panel in granting accelerated approval, a step it can take but does not take routinely.
Sources: FDA · CURE Today
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