A new drug candidate that inhibits production of male hormones anywhere in the body - abiraterone - is showing potential in early trials on prostate cancer patients whose tumors continued to grow despite medical or surgical intervention.

As presented last week at the ESMO Conference Lugano:

"...the drug, called abiraterone, reduced levels of "prostate specific antigen", a marker of cancer activity, and shrank tumors in patients in whom hormone therapy had stopped working and also in patients who had previously been treated with chemotherapy.'

Male hormones (i.e. testosterone) can stimulate the growth of prostate cancer cells. That's why the treatment management is always to suppress the production of such hormones, for example drugs that inhibit testicular production of male hormones (males hormones like testosterone is mainly produced in the testes). But this doesn't prevent the production of male hormones in other parts of the body.

Abiraterone is an oral drug that inhibits an enzyme called CYP450c17, which is critical to the production of the male hormones - not only in the testes, but also at other sources.

The early trials of abiraterone has produced PSA (prostate specific antigen) decline rates by greater than 50% in 60% of pre-docetaxel patients and 50% of post-docetaxel patients - as supported by evidence of tumour shrinkage on scans, drops in circulating tumor cell counts and improvements in symptoms.

Next year, abiraterone will go into Phase III clinical trials. Cougar Biotechnology's prostate cancer drug candidate is abiraterone acetate, dubbed CB7630.

Find more details from the full report at ESMO and the press release at Cougar Biotech.