The US FDA has extended its review timeline for AstraZeneca’s camizestrant combination therapy, pushing back the Prescription Drug User Fee Act (PDUFA) date while it evaluates additional data requested for the application. 

 

The drug is being reviewed for use in combination with a CDK4/6 inhibitor—palbociclib, ribociclib, or abemaciclib—as a first-line treatment for patients with hormone receptor (HR)-positive, HER2-negative advanced breast cancer whose tumours develop an ESR1 mutation.

 

The filing is backed by results from the pivotal SERENA-6 Phase III trial. The FDA previously granted Breakthrough Therapy Designation for the camizestrant combination in May 2025, underscoring its potential importance in this setting.

 

However, momentum has been tempered by regulatory scrutiny. In April 2026, the FDA’s Oncologic Drugs Advisory Committee failed to reach a majority vote supporting the benefit of switching to camizestrant plus a CDK4/6 inhibitor after detection of an ESR1 mutation in circulating tumour DNA (ctDNA) prior to radiographic progression, based on SERENA-6 data.

 

In response, AstraZeneca has submitted further analyses requested by the regulator, including ctDNA clearance data linked to longer-term efficacy outcomes, which will be presented on 02 June at ASCO 2026.

 

Susan Galbraith, Executive Vice President, Oncology Haematology R&D, AstraZeneca, said: “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. 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.”

 

Despite the US delay, the program continues to gain regulatory traction elsewhere. On 22 May, the European Medicines Agency’s Committee for Medicinal Products for Human Use issued a positive opinion recommending approval of the combination based on SERENA-6 results.

 

Camizestrant is already approved in the United Arab Emirates and Saudi Arabia for this indication, with additional regulatory reviews ongoing in Japan and several other markets worldwide.