Hormone-blocking pill slows prostate cancer spread

CHICAGO - A trial of Johnson & Johnson's Zytiga in certain prostate cancer patients showed that it doubled the amount of time they lived without the disease getting worse, potentially offering new hope for patients who see their cancer return.

The trial, involving 1,088 patients who had stopped responding to traditional hormonal drugs but had not been treated with chemotherapy, found that Zytiga slowed the spread of the disease by 58 per cent.

Zytiga is one of several new prostate cancer treatments that may significantly prolong the life of patients by zeroing in more closely on certain mechanisms that help tumors proliferate. New data on the medications are being presented at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago.

The drug's robust results in earlier-stage cancer - it is already approved for men with prostate cancer who previously received chemotherapy - have implications for companies like Dendreon, which sells therapeutic prostate cancer vaccine Provenge, and Medivation, which is developing a drug with a mechanism of action similar to Zytiga's.

The Zytiga trial found that patients given a placebo and the steroid prednisone went a median of 8.3 months before their disease worsened. Patients treated with the steroid and Zytiga were still faring better at the time the data were analyzed, so a comparable statistic was not yet available.

The study's lead investigator, Dr Charles Ryan of the University of California, San Francisco's Helen Diller Family Comprehensive Cancer Center, estimated that the Zytiga patients would enjoy at least 16 months of progression free survival (PFS).

The trial also found that prednisone-only patients lived for a median of 27.2 months. Overall survival for patients treated with Zytiga had also not yet been reached, but J&J estimated that it improved their survival by 33 per cent, or 9 months.

That would clearly surpass the 4.1 month survival benefit demonstrated by Provenge, which was tested in a similar patient population.

"We believe the perception is that this is clearly negative for Provenge," JP Morgan analyst Cory Kasimov said in a research note, while emphasizing that he believes physicians will still see a place for using immunotherapies such as the Dendreon drug.

The Zytiga pre-chemotherapy trial was stopped ahead of schedule in March after it became clear patients were benefiting from the drug, a member of a new class designed to work inside cancer cells to block the production of testosterone, the male hormone that fuels prostate cancer cell growth.

Prostate cancer is the second most common form of cancer in men, with some 30,000 dying from the disease each year in the United States alone and 250,000 globally. Around a third of patients need no treatment, because their disease does not metastasize, or spread, while another third are treated and cured.

But for the remaining patients, the cancer will recur following treatment or spread to the bones, lymph nodes or other parts of the body. Prostate cancer can turn lethal when it spreads and when it resists standard hormonal therapy.

New approval sought


Research presented at ASCO showed that a pivotal trial of Medivation's enzalutamide met all of its secondary goals - including improvements in quality of life.

Medivation and development partner Astellas Pharma, which previously said the experimental drug improved survival by nearly 5 months in a trial of advanced prostate cancer patients, filed in May for US regulatory approval of enzalutamide.

Details released on Saturday included data showing that the Medivation drug, designed to block testosterone from binding to cancer cells, reduced the risk of skeletal-related events, including fractures, by 38 per cent.

Data will also be presented at ASCO from trials of alpharadin, a drug designed to deliver minute, highly-charged doses of radiation to secondary tumors in the bone that is being developed by Bayer AG and Algeta ASA.

J&J expects to file in the second half of this year for US regulatory approval of Zytiga, also known as abiraterone, as a treatment for men with metastatic prostate cancer who have not yet received chemotherapy.

"Clearly, if we're showing greater benefit in the pre-chemotherapy population ... I don't think its unreasonable that they (clinicians) would move it up," said Michael Meyers, head of the drug's development at J&J.

The study also showed that Zytiga significantly delayed the need for pain drugs taken to reduce side effects and eventual chemotherapy.

The drug is currently given for eight months at a cost of around US$44,000 (S$57,000). Barclays estimates peak US Zytiga sales of US$1.5 billion by 2015, with US$700 million from cases where it is used after chemotherapy and US$800 million from patients who have yet to try chemo.

Side effects associated with the drug included cardiac disorders, high blood pressure and increased liver enzyme levels.

J&J's Meyers said the safety profile seen with Zytiga in the latest trial was similar to earlier studies, even though patients were exposed to the drug for nearly twice as long.

He said the side effects "for the most part did not disrupt treatment and were easily managed by routine medical interventions."