The U.S. Food and Drug Administration has extended the review period for AstraZeneca's (NASDAQ: AZN) new drug application for camizestrant in combination with CDK 4/6 inhibitors for treating hormone receptor-positive, HER2-negative advanced breast cancer patients whose tumors have an emergent ESR1 mutation.

The FDA requested additional data to support the application under the Prescription Drug User Fee Act review process. The drug combination is intended for first-line treatment in combination with palbociclib, ribociclib or abemaciclib.

The application is based on results from the SERENA-6 Phase III trial, which were presented at the 2025 American Society of Clinical Oncology Annual Meeting and published in The New England Journal of Medicine. The FDA granted Breakthrough Therapy Designation for the camizestrant combination in May 2025.

In April 2026, the FDA's Oncologic Drugs Advisory Committee did not reach a majority vote supporting the benefit of switching to camizestrant in combination with a CDK4/6 inhibitor after detecting an ESR1 mutation in circulating tumor DNA prior to radiographic progression.

AstraZeneca has provided additional analyses requested by the FDA, including circulating tumor DNA clearance data linked to longer-term efficacy outcomes. This data will be presented on June 2 at the 2026 ASCO meeting.

"We are committed to continuously advancing the clinical landscape in oncology in pursuit of improving outcomes for patients," said Susan Galbraith, Executive Vice President, Oncology Haematology R&D at AstraZeneca.

The European Medicines Agency's Committee for Medicinal Products for Human Use adopted a positive opinion recommending approval of the camizestrant combination on May 22. The drug is approved in the United Arab Emirates and Saudi Arabia, with regulatory applications under review in Japan and other countries.