On September 4, 2026, the Food and Drug Administration granted accelerated approval to camizestrant, an oestrogen receptor antagonist, in combination with a CDK4/6 inhibitor (abemaciclib, palbociclib, or ribociclib) for adults with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative locally advanced or metastatic breast cancer upon detection of oestrogen receptor-1 (ESR1) mutation during aromatase inhibitor and CDK4/6 inhibitor therapy, based on an FDA-authorized test.

FDA also approved the Guardant360 CDx assay as a companion diagnostic device to identify patients with breast cancer with ESR1 mutations for treatment with camizestrant.

Full prescribing information for camizestrant will be posted on Drugs@FDA.

Efficacy and Safety

Efficacy was evaluated in SERENA-6 (NCT04964934), a randomised, double-blind, placebo-controlled, multicenter trial to assess switching to camizestrant in combination with a CDK4/6 inhibitor versus continuing an aromatase inhibitor (AI) in combination with a CDK4/6 inhibitor in adult patients with ER-positive, HER2-negative locally advanced or metastatic breast cancer with detectable ESR1 mutations. The ESR1 mutation status was assessed by blood circulating tumour deoxyribonucleic acid (ctDNA) testing using the Guardant360 CDx assay during first-line treatment with an AI and a CDK4/6 inhibitor. All patients were required to be currently receiving treatment of an AI in combination with a CDK4/6 inhibitor for ≥ 6 months as the initial endocrine based treatment with no evidence of disease progression as per investigator assessment. A total of 315 patients were randomised (1:1) to receive either camizestrant once daily in combination with a CDK4/6 inhibitor or AI (anastrozole or letrozole) orally once daily in combination with a CDK4/6 inhibitor.

The primary efficacy outcome measure was investigator-assessed progression-free survival (PFS) per RECIST v1.1. An additional efficacy outcome measure included overall survival (OS). Median PFS was 16 months (95% CI: 12.7, 18.2) in the camizestrant and CDK4/6 inhibitor arm and 9.2 months (95% CI: 7.2, 9.5) in the AI and CDK4/6 inhibitor arm (Hazard ratio 0.44 [95% CI: 0.31, 0.60]; p-value < 0.00001). At the time of the PFS analysis, OS data were not mature.

The prescribing information includes a boxed warning for the risk of arrhythmia due to QTc interval prolongation when concomitantly used with QTc interval prolonging drugs, as well as warnings and precautions for bradycardia and embryo-fetal toxicity.

Recommended Dosage

The recommended camizestrant dose is 75 mg orally once daily, with or without food, until disease progression or unacceptable toxicity. Administer camizestrant in combination with a CDK4/6 inhibitor (abemaciclib, palbociclib, or ribociclib). Continue the CDK4/6 inhibitor at the same dosage as when the ESR1 mutation was detected. Refer to the prescribing information of the CDK4/6 inhibitor for additional dosing information.

Camizestrant in combination with a CDK4/6 inhibitor (abemaciclib, palbociclib, or ribociclib) is being granted accelerated approval based on PFS measured from detection of ESR1 mutation. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s). For more information on ongoing accelerated approvals in oncology, refer to Project Confirm.

This review was conducted under Project Orbis, an initiative of the FDA Oncology Center of Excellence. Project Orbis provides a framework for concurrent submission and review of oncology drugs among international partners. For this review, FDA collaborated with the Australian Therapeutic Goods Administration (TGA), the Brazilian Health Regulatory Agency (ANVISA), Health Canada, Singapore’s Health Sciences Authority (HSA), and Switzerland’s Swissmedic. The application reviews may be ongoing at the other regulatory agencies.

This application was discussed at an Oncology Drugs Advisory Committee meeting. This review used the Assessment Aid, a voluntary submission from the applicant to facilitate the FDA’s assessment.

This application was granted standard review. Camizestrant received breakthrough therapy designation. A description of FDA expedited programs is in the Guidance for Industry: Expedited Programs for Serious Conditions-Drugs and Biologics.

Healthcare professionals should report all serious adverse events suspected to be associated with the use of any medicine and device to FDA’s MedWatch Reporting System or by calling 1-800-FDA-1088.

For assistance with single-patient INDs for investigational oncology products, healthcare professionals may contact OCE’s Project Facilitate at 240-402-0004 or email OncProjectFacilitate@fda.hhs.gov.

Source: FDA