The US Food and Drug Administration has delayed a decision on AstraZeneca’s experimental breast cancer pill camizestrant, extending its review period to examine additional data submitted by the pharmaceutical company.
The extension follows a vote on 30 April 2026 in which a majority of the FDA’s Oncologic Drugs Advisory Committee (ODAC) found against the drug’s benefit-risk profile when used in combination with a CDK4/6 inhibitor for first-line treatment of certain advanced breast cancers. The panel voted 6-3 against the combination, but its concerns centred on the design of the pivotal Phase III trial, not on questions of safety or efficacy.
Advisory panel questions trial design
The main issue raised by the panel was the design of the SERENA-6 trial. Committee members questioned the clinical meaningfulness of the progression-free survival (PFS) data and noted the absence of overall survival (OS) data, which are still maturing. The FDA had previously cautioned AstraZeneca that switching therapy before radiographic progression – as the trial protocol required – needed strong justification, because patients might lose the benefit of their current effective regimen.
In the SERENA-6 trial, patients with hormone receptor (HR)-positive, HER2-negative advanced breast cancer who had developed emergent ESR1 mutations were switched from an aromatase inhibitor plus a CDK4/6 inhibitor to camizestrant plus a CDK4/6 inhibitor. The trial showed a 56% reduction in the risk of disease progression or death compared with standard care. Median PFS was 16.0 months in the camizestrant arm versus 9.2 months in the control arm. A subsequent analysis also demonstrated a statistically significant benefit in time to second disease progression (PFS2): 25.7 months for the camizestrant combination compared with 19.1 months for standard treatment.
Company submits further data
AstraZeneca confirmed it has submitted additional analyses requested by the FDA to support its new drug application. These include data on longer-term efficacy outcomes, specifically ctDNA clearance data linked to those outcomes, which are scheduled to be presented at a conference on 2 June. The FDA has extended the Prescription Drug User Fee Act (PDUFA) date to allow time to assess this new information.
Susan Galbraith, a senior executive at AstraZeneca, said: “We look forward to continuing the dialogue with the FDA in order to bring the benefits of camizestrant with this innovative treatment strategy to eligible patients in the US as quickly as possible.”
How camizestrant works and trial data
Camizestrant is a next-generation oral selective estrogen receptor degrader (SERD) and a pure estrogen receptor antagonist. It binds to the oestrogen receptor and promotes its degradation, blocking oestrogen signalling that drives cancer cell growth. This mechanism is distinct from older therapies that only block the receptor or reduce oestrogen levels. The drug is being developed for patients with HR-positive, HER2-negative advanced breast cancer whose tumours carry ESR1 mutations, a common cause of resistance to standard endocrine therapy.
The FDA granted camizestrant Breakthrough Therapy Designation in May 2025 based on positive interim results from the SERENA-6 trial. It also received Fast Track designation in May 2022 following Phase I results. Earlier clinical work, including the Phase I SERENA-1 trial and the Phase II SERENA-2 trial, showed that camizestrant is well tolerated and offers a statistically significant improvement in PFS over the existing SERD fulvestrant.
Breast cancer is the second most common cancer globally and a leading cause of cancer deaths, with more than two million diagnoses and over 665,000 deaths reported in 2022.
In Europe, the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) issued a positive opinion recommending approval of camizestrant in combination with a CDK4/6 inhibitor last week. The drug will be marketed in Europe under the brand name Etcamah. Camizestrant is already approved for this indication in the United Arab Emirates and Saudi Arabia, and regulatory applications are under review in Japan and other countries.