A trial looking at GDC0941 and anastrozole for oestrogen positive breast cancer (OPPORTUNE)

Please note - this trial is no longer recruiting patients. We hope to add results when they are available.

Cancer type:

Breast cancer




Phase 2

This trial is looking at a drug called GDC0941 and a hormone therapy called anastrozole for breast cancer that is positive for oestrogen hormone receptors (ER positive). This trial is open to women whose periods have stopped permanently (they are post menopausal).

Doctors usually treat ER positive breast cancer in post menopausal women with surgery, followed by a hormone treatment called anastrozole. Sometimes they give anastrozole before surgery to shrink the cancer.

GDC0941 is a type of biological therapy. It is a cancer growth blocker. It stops signals that cancer cells use to divide and grow. We know from laboratory studies that it may help to stop cancer cells from dividing and growing.

The researchers think the combination of GDC0941 and anastrozole may work well for women with ER positive breast cancer. In this trial, before your surgery you have either anastrozole only or GDC0941 and anastrozole.

The aims of this trial are to find out

  • How well the combination of GDC0941 and anastrozole works for women with ER positive breast cancer
  • How safe this combination is
  • What the side effects are

Who can enter

You may be able to enter this trial if you are a woman and

You cannot enter this trial if you

  • Have breast cancer that has spread to another part of your body
  • Have inflammatory breast cancer
  • Are already having treatment for your breast cancer – you may join if you have had treatment to another cancer in your breast, as long as it was at least a year ago
  • Are taking hormone replacement therapy (HRT) Open a glossary item – you may join if you stop taking HRT at least a month before you give your first tissue sample (biopsy) in this trial
  • Have had treatment that reached your whole body (systemic treatmen Open a glossary itemt) for any other cancer in the past year
  • Have taken an experimental drug as part of another trial in the month before agreeing to take part in this trial
  • Have serious breathing problems
  • Have serious heart problems
  • Have diabetes that is not controlled by medication
  • Are taking medication to thin your blood, such as warfarin or heparin
  • Have a problem with your digestive system Open a glossary item that could affect the way you absorb drugs
  • Have hepatitis B or hepatitis C and the infection is causing problems
  • Have any other serious liver problem
  • Have any other medical condition that could affect you taking part in this trial

Trial design

This is a phase 2 trial. It will recruit 141 women. This is a randomised trial. The women taking part are put into treatment groups by a computer. Neither you nor your doctor will be able to decide which group you are in.

There are 2 groups in this trial. Women in group 1 have GDC0941 and anastrozole for 2 weeks before surgery. Women in group 2 have anastrozole for 2 weeks before surgery.

OPPORTUNE trial diagram

If you agree to take part in this study, the researchers will ask you to donate a sample of tissue and a blood sample taken before you start treatment and when you have surgery to remove your cancer.

Hospital visits

You see the doctor to have some tests before taking part in this trial. These tests include

Before surgery you see the doctor to have the same tests.

About 2 to 4 weeks after surgery you see the doctor to see how you are.

Side effects

GDC0941 is a new drug and there may be side effects we don’t know about. The most common side effects reported include

The most common side effects of anastrozole are

  • Stiffness of the joints
  • Tiredness
  • Hot flushes Open a glossary item
  • Vaginal dryness and irritation
  • Slight hair thinning
  • Headache

We have more information about anastrozole in our cancer drugs section.

Recruitment start:

Recruitment end:

How to join a clinical trial

Please note: In order to join a trial you will need to discuss it with your doctor, unless otherwise specified.

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Chief Investigator

Prof Peter Schmid

Supported by

Brighton and Sussex University Hospitals NHS Trust
Experimental Cancer Medicine Centre (ECMC)
NIHR Clinical Research Network: Cancer

Freephone 0808 800 4040

Last review date

CRUK internal database number:

Oracle 9446

Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

Harriet wanted to try new treatments

Picture of Harriet

“I was keen to go on a clinical trial. I wanted to try new cancer treatments and hopefully help future generations.”

Last reviewed:

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