FDA Extends Review of AstraZeneca’s Camizestran

AstraZeneca’s camizestrant has faced a regulatory setback in the U.S., with the FDA extending its review, seeking clearer evidence that early intervention improves long-term outcomes for patients with advanced breast cancer.

The U.S. FDA has extended its review of AstraZeneca’s camizestrant application, delaying a decision on the experimental breast cancer treatment while it examines the requested additional data. The new drug application (NDA) filing covers camizestrant in combination with a cyclin-dependent kinase (CDK) 4/6 inhibitor — granted Breakthrough Therapy Designation in May 2025 — for the first-line treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer with emergent estrogen receptor 1 (ESR1) mutations (1).

Camizestrant is an investigational, potent, next-generation oral selective estrogen receptor degrader (SERD) and complete estrogen receptor (ER) antagonist in Phase III trials for HR-positive breast cancer. AstraZeneca is testing it as a monotherapy, with CDK4/6 inhibitors (palbociclib, ribociclib, or abemaciclib) across multiple clinical trials to address unmet needs in HR-positive, HER2-negative disease. It has shown anti-cancer activity in preclinical models — including those with ER-activating mutations — with significantly improved progression-free survival versus fulvestrant (Faslodex), including in patients with ESR1 mutations. Multiple trials have demonstrated tolerability of camiszestrant with a promising anti-tumour profile, both as monotherapy and in combination with CDK4/6 inhibitors.

The FDA extension follows an advisory committee meeting in April, when the FDA’s Oncologic Drugs Advisory Committee did not reach a majority in favour of the benefit–risk profile of camizestrant in combination with CDK4/6 inhibitor (2). The panel’s concerns centered on the design of the SERENA-6 Phase III trial and whether switching therapy after detection of ESR1 mutations in circulating tumour DNA, but before radiographic progression, demonstrated enough long-term benefit (3). The company said it has submitted additional analyses requested by the agency, including ctDNA clearance data linked to longer-term efficacy outcomes. The findings are due to be presented at ASCO 2026 on 2 June.

“We are committed to continuously advancing the clinical landscape in oncology in pursuit of improving outcomes for patients. The SERENA-6 treatment strategy epitomises this approach by monitoring patients for the emergence of ESR1 mutations in ctDNA and testing if a switch of endocrine backbone therapy at this point improves outcomes,” said Susan Galbraith, AstraZeneca’s Executive Vice President of Oncology Haematology R&D, in a press release (1). “We look forward to continuing the dialogue with the FDA to bring the benefits of camizestrant with this innovative treatment strategy to eligible patients in the US as quickly as possible.”

The U.S. delay comes just days after the European Medicines Agency’s Committee for Medicinal Products for Human Use adopted a positive opinion recommending approval of the same camizestrant combination in this setting (4). AstraZeneca said the treatment is already approved in the United Arab Emirates and Saudi Arabia, while applications remain under review in Japan and other markets.

References

1. AstraZeneca. US FDA Decision Date Extended for SERENA-6 Filing of Camizestrant to Enable Review of Additional Data. Press Release, May 27, 2026.

2. AstraZeneca. Update on FDA Advisory Committee Vote on Camizestrant in Combination with a CDK4/6 Inhibitor for Advanced HR-Positive Breast Cancer. Press Release, April 30, 2026.

3. FDA. Oncologic Drugs Advisory Committee (ODAC) Meeting: Combined FDA and Applicant ODAC Briefing Document. April 30, 2026.

4. AstraZeneca. Camizestrant in Combination with a CDK4/6 Inhibitor Recommended for Approval in the EU by CHMP for 1st-Line Advanced ER-Positive Breast Cancer. Press Release, May 22, 2026.