A trial looking at irosustat to treat advanced womb cancer

Cancer type:

Secondary cancers
Womb (uterine or endometrial) cancer




Phase 2
This trial compared irosustat with megestrol acetate to treat women with advanced womb cancer or womb cancer that had come back. Womb cancer is sometimes called endometrial or uterine cancer. 
It was for women who:
  • had been through the menopause Open a glossary item
  • had womb cancer that is sensitive to the female hormone oestrogen (oestrogen receptor positive Open a glossary itemor ER positive)
  • could not have surgery or radiotherapy 

More about this trial

Some women have megestrol acetate for womb cancer that has spread or come back after treatment. Megestrol acetate (Megace) is a type of hormone therapy. But sometimes it stops working. So, researchers are looking for ways to improve treatment. In this trial they looked at irosustat.
Irosustat (also known as BN83495) is another type of hormone therapy. It also works by blocking sex hormones but in a slightly different way. It was a new drug when researchers did this trial. They thought it might be better at slowing the growth of cancer than megestrol acetate. But they weren’t sure, so wanted to find out more. 
The aims of this trial were to: 
  • find out if irosustat worked better than megestrol acetate 6 months after treatment started
  • learn more about the side effects

Summary of results

The trial team found that irosustat didn’t work as well as they had hoped. Instead they found that megestrol acetate worked better to slow the growth of the cancer. As a result, this trial stopped earlier than planned. 
This small phase 2 trial took place worldwide. 71 women took part. They were put into 1 of 2 treatment groups at random, and:
  • 36 had irosustat tablets
  • 35 had megestrol acetate tablets
Everyone had treatment for as long as it was working and the side effects weren’t too bad.
The researchers published the results in February 2017.
The researchers did an early analysis of the results in June 2011. They looked at the number of women living whose cancer hadn’t got worse after 6 months of treatment. They found this was:
  • just under 4 out of 10 women (36%) who had irosustat
  • just over 5 out of 10 women (54%) who had megestrol acetate
Based on this analysis, they decided to stop the trial early. This was because women taking irosustat did worse compared to women having megestrol acetate.
The researchers looked at how well irosustat worked. They found:
  • in 3 women the cancer went away a little bit 
  • in 17 women the cancer stayed the same 
  • in 14 women the cancer got worse
  • they didn’t have the results for 1 woman
They looked at how well megestrol acetate worked. They found:
  • in 2 women the cancer went away completely
  • in 10 women the cancer went away a little bit
  • in 12 women the cancer stayed the same
  • in 8 women the cancer got worse
  • they didn’t have the results for 2 women 

The researchers also looked at the average length of time before the cancer started to grow again. On average this was:       

  • 16 weeks in women who had irosustat
  • 40 weeks in women who had megestrol acetate
The researchers also looked at:
  • how well the cancer responded to treatment
  • how long women lived for 
But they didn’t find a significant difference in either of these. 
Side effects
The side effects of both irosustat and megestrol acetate were mild. The most common side effect for both drugs was dry skin. Although women who had irosustat had more problems with this. 
The trial team concluded that irosustat didn’t help women with advanced womb cancer or womb cancer that had come back. But it did confirm that megestrol acetate worked for some women.  
This trial has increased what we know about what works and what doesn’t for advanced womb cancer.
We have based this summary on information from the research team. The information they sent us has been reviewed by independent specialists (peer reviewed Open a glossary item) and published in a medical journal. The figures we quote above were provided by the trial team who did the research. We have not analysed the data ourselves.

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

Dr John Green

Supported by

Experimental Cancer Medicine Centre (ECMC)

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Freephone 0808 800 4040

Last review date

CRUK internal database number:


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

Charlie took part in a trial to try new treatments

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“I think it’s really important that people keep signing up to these type of trials to push research forward.”

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