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Trial Tests New Study Medicine Plus Letrozole for Advanced Breast Cancer

Researchers will explore whether giving LEE011 with letrozole better treats hormone receptor-positive, HER2-negative metastatic disease

April 22, 2014

Written By Marcia Frellick
Reviewed By Ruth Oratz, MD, FACP

Researchers seek 500 women who have hormone receptor-positive, HER2-negative advanced breast cancer to take part in a phase III study testing a new medicine pair. Women who are postmenopausal, or no longer get their periods, may qualify to enroll in the study if they have not yet received treatment for advanced breast cancer.

Background and Goals

The purpose of this trial is to learn if a new study medicine  called LEE011, given together with letrozole (Femara) — an FDA-approved aromatase inhibitor, better controls hormone receptor-positive, HER2-negative metastatic breast cancer than letrozole alone. Aromatase inhibitors, AIs, are standard-of-care treatment for postmenopausal women with hormone-sensitive breast cancer.

Enzymes in the body called cyclin-dependent kinases can be overactive in people with breast cancer, causing cancer cells to grow and divide out of control. Researchers developed LEE011 to target these enzymes, specifically CDK 4 and 6.

The main goal of this study is to measure progression-free survival, PFS, for up to 25 months. PFS is the length of time after receiving the study medicine that the disease is still present but does not worsen.

In addition, researchers will evaluate overall survival, or the time from start of participation in the study to death from any cause, for up to about 69 months. They will also test how well women tolerate LEE011 and how safe it is based on the type of negative side effects that arise, how often they occur and how severe they are.

Because LEE011 is a new medicine being studied, it has not been proven safe or effective. There is no guarantee it will be approved by the FDA. Treatment will continue as long as you benefit from it, but can be stopped if you have any unacceptable side effects, or if you or your doctor decide it is best for you to do so.


The study is randomized, so participants will be assigned at random to one of two treatment groups:

  • LEE011 plus once-daily letrozole taken by mouth (3 weeks on, 1 week off)
  • placebo plus FDA-approved letrozole taken once a day by mouth (3 weeks on, 1 week off)

The study is double-blinded meaning neither you, your caregiver, the investigator nor the person or people who assess outcomes will know which treatment you are getting. That helps eliminate any bias in figuring out whether the treatment is working.

All study participants will receive medical care from healthcare professionals at a clinical trial site.


You may be able to take part if you

  • are age 60 or older
  • are younger than 60 but have not had a period for at least 12 months, in the absence of chemotherapy, tamoxifen, toremifen, or methods to stop your ovaries from working
  • have advanced, recurrent or metastatic, breast cancer but have not yet received  therapy for the disease
  • have at least one lesion that can be measured OR at least one lytic bone lesion, an area where bone appears to have been destroyed by disease, leaving a clear area shown on imaging scans

You may not be eligible if you

  • were treated with a CDK4/6 inhibitor
  • received any prior anti-cancer therapy — including chemotherapy — for advanced disease, with the exception of surgery
  • have a documented history of congestive heart failure
  • have documented cardiomyopathy, or disease of the heart muscle
  • have a history of cardiac arrhythmias, or abnormal heart beats

For more information or to find out if you are eligible, talk with your doctor about trial NCT01958021 on

Study Locations

This study is being conducted in 294 locations in the US and internationally. Enrollment started in December 2013 and is expected to finish in January 2017. Some sites are recruiting now and others will recruit later. For full details and contact information, visit