FDA Panel Votes Against AstraZeneca's Breast Cancer Drug Camizestrant

An FDA advisory panel voted 6 to 3 against supporting the risk-benefit profile of AstraZeneca's experimental oral breast cancer treatment camizestrant, concluding the drug did not show a "meaningful benefit" for patients with HR-positive, HER2-negative metastatic breast cancer whose disease had not progressed on existing therapy.

The FDA's Oncologic Drugs Advisory Committee (ODAC) determined that AstraZeneca has not demonstrated its oral SERD camizestrant offers a clinically meaningful benefit for treating HR-positive, HER2-negative metastatic breast cancer when a tumor ESR1 mutation is detected before radiographic progression on first-line therapy. While advisory panel votes are not binding, the FDA typically follows their recommendations. A final agency decision is expected later.

In the SERENA-6 study, camizestrant showed a 56% improvement in progression-free survival (PFS) for switching to camizestrant, used on top of a CDK4/6 inhibitor, compared with continuing treatment with an aromatase inhibitor and a CDK4/6 drug. The drug delayed disease progression by more than six months — patients lived a median of 16 months without progression, compared with 9.2 months for those on the current standard of care. Overall survival data were immature, with no sign of detriment observed.

The FDA took issue with AstraZeneca's trial design, arguing it does not address whether this first-line switch approach provides long-term benefit compared with the standard practice of waiting until disease progression to use an oral SERD drug like camizestrant. Although camizestrant extended median PFS by 6.8 months, the FDA questioned its clinical meaningfulness because it was not measured from a standard time point. Additionally, SERENA-6 did not allow crossover, meaning no patient in the control arm was allowed to receive camizestrant after progression.

The FDA also flagged concerns that if implemented, patients would need to be monitored constantly for ESR1 mutations with only few becoming eligible for camizestrant. The agency expanded its caution beyond this application, fearing approving camizestrant would open a questionable precedent with "far-reaching implications for many future patients and many future trials."

AstraZeneca argued that waiting until disease progression to give an oral SERD is less effective because tumors at that time have increased genomic alterations and become harder to treat. The company said it was "disappointed" by the outcome but expressed confidence in its trial results and the drug's potential benefit for patients.

AstraZeneca shares fell 1.6% in London following the vote. The decision creates "regulatory overhang and a dent to investor sentiment," analysts said, noting a decreased likelihood of approval in the SERENA-6 setting. The setback affects AstraZeneca's plan of introducing a drug with potential for $5 billion in peak annual sales.