European regulator backs AstraZeneca breast cancer pill after US setback

The European Medicines Agency took AstraZeneca a step closer to approval for a breast cancer pill aimed at patients whose tumors carry ESR1 mutations, a group that can develop resistance to hormone therapy and may need a treatment switch before the cancer visibly worsens. If the European Commission follows the agency’s recommendation, the drug would reach clinics in the European Union under the brand name Etcamah.

On May 21, the EMA’s Committee for Medicinal Products for Human Use adopted a positive opinion on camizestrant and recommended marketing authorization for ER-positive, HER2-negative locally advanced or metastatic breast cancer in patients with ESR1 gene mutations. The recommendation covers use with palbociclib, ribociclib or abemaciclib, placing the drug squarely in the fast-moving CDK4/6 inhibitor treatment landscape that already anchors many advanced breast cancer regimens.

AstraZeneca said the committee’s view was based on the Phase III SERENA-6 trial, which tested camizestrant as a ctDNA-guided switch strategy. In that approach, treatment changes when an ESR1 mutation emerges in blood testing, before radiographic progression shows up on scans. The company said the trial showed a 56% reduction in the risk of disease progression or death and delayed deterioration in quality of life by nearly 18 months.

That promise now meets the harder question regulators and oncologists ask next: how durable is the benefit, how manageable are the side effects, and how much will it cost health systems to adopt it broadly. The European opinion is an important step, but it is not the final legal authorization. Even with a favorable view from CHMP, payers and doctors will still want longer follow-up on survival and real-world tolerability before making the drug a routine option.

The European decision also stands in contrast with the U.S. Food and Drug Administration’s Oncologic Drugs Advisory Committee, which did not reach a majority vote in favor of camizestrant’s benefit-risk profile in first-line treatment for patients with hormone receptor-positive, HER2-negative advanced breast cancer whose tumors have an emergent ESR1 mutation. AstraZeneca said the U.S. advisers’ concerns centered on trial design rather than the drug’s safety or effectiveness.

That split matters because the same data can move differently through two major regulators. For AstraZeneca, a positive opinion in Europe offers regulatory momentum after the U.S. setback and could shape how quickly the company advances the drug into practice, while keeping attention fixed on a central oncology challenge: finding the moment to change treatment before resistance becomes visible on scans.