Zytiga Extends Lives of Prostate Cancer Patients, Study Says

Zytiga, made by Johnson & Johnson (JNJ) unit Centocor Ortho Biotech, gave men with advanced prostate cancer an average of four months of extra life, according to Phase III trial results published in the New England Journal of Medicine on Wednesday.

The medicine, also known as abiraterone acetate, is a pill that targets a protein called cytochrome P450 17A1 (CYP17A1), which plays an important role in the production of testosterone. The drug works by decreasing the production of this hormone that would stimulate cancer cells to continue growing.

The treatment was discovered at The Institute of Cancer Research, or ICR, in what is now the Cancer Research UK Cancer Therapeutics Unit. It was first studied in trials at The Royal Marsden Hospital in London.

"Men with advanced prostate cancer have very few therapies available to them and sadly around 10,000 patients in the U.K. die each year from this disease," said the study's chief investigator and lead author, Johann de Bono of the ICR and The Royal Marsden.

"We are thrilled that a drug discovered at The Institute of Cancer Research has been proven to significantly extend life for many men, giving doctors a valuable new treatment option," de Bono said in a statement.

Zytiga received U.S. approval last month in combination with prednisone to treat patients with a certain type of late-stage prostate cancer in patients who have been previously treated with chemotherapy.

The manufacturer has also applied for regulatory agency approvals in Europe, but for now the drug is not available to patients in the U.K.

In prostate cancer, the male sex hormone testosterone stimulates prostate tumors to grow. Drugs or surgery are used to reduce testosterone production or to block testosterone's effects.

Still, sometimes prostate cancer can continue to grow even when testosterone levels are low. Men with these cancers are said to have castration-resistant prostate cancer, which is the type of cancer Zytiga was approved to treat.

Hormone treatments that block the testes' production of testosterone usually stop benefiting patients after a few years, leading to the assumption that as tumors progressed they developed the ability to grow independently of testosterone.

However, it was known that the adrenal glands also produce testosterone, suggesting that this was providing fuel to some cancer cells.

Scientists elsewhere had also measured higher levels of enzymes involved in testosterone synthesis inside prostate tumor tissue, giving rise to a new theory that some cancers were able to produce their own testosterone.

Professor Mike Jarman and his team at ICR designed Zytiga to have a different mechanism of action from standard hormone treatmentsblocking the production of male hormones in all tissues, not just the testes, by targeting an enzyme involved in hormone synthesis called CYP17.

"From the success of this study, it's now clear that men with advanced prostate cancer can still benefit from treatments targeting male hormones. This has corrected 40 years of misunderstanding about this disease and we hope it will lead to the development of more second-line hormone treatments for these men, much like those used successfully to treat breast cancer," ICR Chief Executive Professor Alan Ashworth said in a statement.

The study was designed to assess overall survival and showed that men given the placebo survived an average of 11 months, while men given Zytiga survived for nearly 15 months.

Pain eased during the trial for a much greater number of patients taking Zytiga than the placebo.