for people ages 18-130 (full criteria)
at San Francisco, California and other locations
study started
estimated completion



The study is intended to show superiority of AZD9833 in combination with CDK4/6 inhibitor (palbociclib or abemaciclib) versus aromatase inhibitors (anastrozole or letrozole) in combination with CDK4/6 inhibitor in patients with hormone receptor-positive (HR-positive), human epidermal growth factor receptor 2-negative (HER2-negative) metastatic breast cancer with detectable ESR1 mutation

Official Title

A Phase III, Double-blind, Randomised Study to Assess Switching to AZD9833 (a Next Generation, Oral SERD) + CDK4/6 Inhibitor (Palbociclib or Abemaciclib) vs Continuing Aromatase Inhibitor (Letrozole or Anastrozole)+ CDK4/6 Inhibitor in HR+/HER2-MBC Patients With Detectable ESR1Mutation Without Disease Progression During 1L Treatment With Aromatase Inhibitor+ CDK4/6 Inhibitor- A ctDNA Guided Early Switch Study


A Randomised, Multicentre, Double-Blind, Phase III study will evaluate the safety and efficacy of AZD9833 (next generation oral SERD) in combination with CDK4/6 inhibitor (palbociclib or abemaciclib) versus aromatase inhibitor (anastrozole or letrozole) in combination with CDK4/6 inhibitor for the treatment of patients with HR-positive, HER2- negative metastatic breast cancer with detectable ESR1 Mutation. The goal of the study is to demonstrate superiority of AZD9833 over anastrozole or letrozole in the context of combination with palbociclib or abemaciclib


ER-Positive HER2-Negative Breast Cancer Metastatic Breast Neoplasms Neoplasms by Site Neoplasms Breast Diseases Physiological Effects of Drugs Randomised Multicentre Double-Blind Phase III AZD9833 Next Generation Oral SERD Anastrozole Letrozole Palbociclib Abemaciclib Antagonists Antineoplastic Agents Estrogen Receptor Antagonists Hormone Antagonists camizestrant ESR1m Switch Treatment Endocrine Therapy Endocrine Resistance Disease Progression Hormones Prolactin Release-Inhibiting Factors Luteinizing hormone-releasing hormone (LHRH) agonist


You can join if…

Open to people ages 18-130

  • Proven diagnosis of adenocarcinoma of the breast with evidence of locoregionally recurrent or metastatic disease not amenable to resection or radiation therapy with curative intent.
  • Documentation of histologically confirmed diagnosis of estrogen receptor positive (ER+) /HER2- breast cancer based on local laboratory results.
  • Currently on AI (letrozole or anastrozole) + CDK4/6 inhibitor (palbociclib or abemaciclib) ± LHRH as the initial endocrine based treatment for advanced disease
  • Eastern Cooperative Oncology Group performance status of 0 or 1.
  • ESR1m positive detected by central testing of ctDNA
  • Willingness and ability to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures.
  • Adequate organ and marrow function

You CAN'T join if...

  • Advanced, symptomatic, visceral spread, that are at risk of life-threatening complications in the short term.
  • Known active uncontrolled or symptomatic CNS metastases, carcinomatous meningitis, or leptomeningeal disease.
  • Any evidence of severe or uncontrolled systemic diseases which, in the investigator's opinion, makes it undesirable for the participant to participate in the study or that would jeopardize compliance with the protocol.
  • Patient with known or family history of severe heart disease
  • Previous treatment with AZD9833, investigational SERDs or fulvestrant.
  • Currently pregnant (confirmed with positive pregnancy test) or breastfeeding.
  • Persistent non-haematological toxicities (CTCAE Grade > 2) caused by CDK4/6 inhibitor and/or AI treatment.


  • Research Site not yet accepting patients
    San Francisco California 94143 United States
  • Research Site not yet accepting patients
    Santa Rosa California 92805 United States


accepting new patients
Start Date
Completion Date
Phase 3
Study Type
Last Updated