Abiraterone, the prostate cancer drug that’s going from strength to strength

Abiraterone

Zytiga, the commercial name of the ICR-discovered abiraterone

The prostate cancer drug abiraterone is one of the big success stories for The Institute of Cancer Research in recent years, transforming the lives of men suffering from the most severe form of prostate cancer.

Abiraterone was discovered and developed at the ICR in London, and was approved in 2011 to treat men with advanced metastatic prostate cancer whose disease no longer responds to chemotherapy. A study published in the Journal of European Urology has now announced updated results for an ongoing trial into the drug, and they make interesting reading.

The international phase III trial, COU-AA-302, was led in the UK by Professor Johann de Bono, professor of experimental cancer medicine at the ICR and honorary consultant at The Royal Marsden Hospital. The trial looked at 1,088 men with metastatic castration-resistant prostate cancer who had mild or no symptoms.

The new study followed up on patients receiving treatment for over two years to assess abiraterone’s effectiveness and long-term safety in patients with advanced prostate cancer.

The trial started in 2009 and evaluated two treatment options for men with metastatic prostate cancer: abiraterone with an immune-suppressing steroid called prednisone, or prednisone on its own.

They selected patients who had already received treatment for their prostate cancer, but hadn’t yet been given chemotherapy, to see if abiraterone could perform as well in prostate cancer patients before chemotherapy as after.

The trial demonstrated that abiraterone blocked tumour growth for significantly longer than prednisone alone, and the provisional data for abiraterone was so strong that in 2012, the trial was changed so those on the prednisone arm could also be offered the drug.

In the new, long-term results, the researchers found that abiraterone delayed patients’ tumours from getting worse by twice as long as the placebo treatment, from 8.2 months to 16.5 months; the drug also improved overall survival, but this increase didn’t reach statistical significance.

The drug, marketed as Zytiga by Janssen, reduced the amount of pain men were feeling from their disease, allowing them to delay morphine treatment, and it also increased the average time before they received chemotherapy from 16.8 to 26.5 months. They also found that abiraterone did not cause any further side-effects during long-term treatment compared with previous trials.

The study shows that abiraterone is safe for patients to take for a prolonged period of time and that the drug could help men with advanced prostate cancer before chemotherapy treatment.

And another study led by Professor de Bono in European Urology has used a prognostic model based on data from another clinical trial, COU-AA-301, to help identify men with advanced prostate cancer where chemotherapy hasn’t worked, but who could benefit from abiraterone.

The model uses six clinically assessed parameters, including measuring blood samples for compounds linked to cancer, and whether the cancer had spread to the liver, to classify prostate cancer patients into groups based on their predicted response to treatment: good, intermediate and poor. But while the model successfully predicted response to abiraterone in men who had already received chemotherapy, Professor de Bono’s study found the model was less reliable for predicting response patients where abiraterone was administered first.

Patients predicted to show a ‘good’ response to abiraterone lived an average of 3.8 years, almost a year longer than the 2.9 years for patients whose treatment response was classified as either intermediate or poor. These findings are encouraging as they show the drug can extend life without prior chemotherapy, and the model could show which men will benefit most, but more testing is needed to ensure the model is accurate and reliable.

These two studies show that abiraterone could be beneficial to a wider range of prostate cancer patients than are currently approved to take the drug, and why it’s so important to continue researching already successful treatments.

It will be interesting to see if NICE takes notice of the accumulating data around abiraterone when it decides whether the drug should be available to many more men before they have had chemotherapy.

NICE began its appraisal process in November and will look at all the available evidence before making a decision, which could come as early as autumn 2014, so hopefully this impressive drug will be approved for more prostate cancer patients soon.

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