SMX22-002: Locally Advanced or Metastatic ER+/HER2- Breast Cancer with an ESR1 Mutation - Clinical Trial

What is the Purpose of this Study?

We are doing this study to find out if an experimental drug called lasofoxifene (the study drug) is a safe and effective option for breast cancer. We want to see if the study drug combined with another drug called abemaciclib has better results than treatment with abemaciclib plus fulvestrant.

What is the Condition Being Studied?

Locally Advanced or Metastatic ER+/HER2- Breast Cancer

Who Can Participate in the Study?

Adults ages 18+ who:

  • Are diagnosed with estrogen receptor-positive (ER+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer
  • Have a documented ESR1 gene mutation
  • Have not received more than 1 line of chemotherapy in the past, and not more than 2 lines of treatment altogether

For more information about who can join this study, please contact the study team at

Age Group

What is Involved?

If you choose to join this study, you will get a random assignment (like a coin flip) to 1 of 2 groups:

  • One group will get the study drug plus abemaciclib
  • The other group will receive fulvestrant plus abemaciclib

All study participants will:

  • Have blood draws
  • Have heart scans (EKGs)
  • Have imaging scans
  • Answer questionnaires
  • Complete drug dosing diaries
  • Give us permission to store your tissue samples

After completing the study regimen, we will call you every 6 months to see how you are doing.

Study Details

Full Title
An Open Label, Randomized, Multicenter Study Comparing the Efficacy and Safety of the Combination of Lasofoxifene and Abemaciclib to the Combination of Fulvestrant and Abemaciclib for the Treatment of Pre-and Postmenopausal Women and Men with Locally Advanced or Metastatic ER+/HER2- Breast Cancer with an ESR1 Mutation
Principal Investigator
Medical Oncologist
Protocol Number
IRB: PRO00112602
NCT: NCT05696626
Phase III
Enrollment Status
Open for Enrollment