New results from a phase II clinical trial of the prostate cancer drug abiraterone suggest that it may help men with advanced disease who have tried standard treatments.
However, a Cancer Research UK clinician cautioned that there were still questions to be answered from ongoing studies about how best to use the drug.
Abiraterone was discovered in the Cancer Research UK Centre for Cancer Therapeutics at The Institute of Cancer Research (ICR) and is taken once a day as four pills.
The latest trial, which was led by the ICR and the Royal Marsden NHS Foundation Trust, is the first to investigate the drug in men with such advanced prostate cancer.
A total of 47 men were recruited for the trial, all of whom had late-stage castration-resistant prostate cancer, which means that their disease was advanced and their tumours were no longer responsive to androgen deprivation therapy. In almost all cases, the men's cancer had spread to their bones.
All of the participants had already received hormone therapy and the chemotherapy drug docetaxel, but were no longer responding to those treatments.
By the end of the study period, researchers found that around three-quarters of men had experienced a drop in levels of prostate specific antigen (PSA), which is often raised in men with prostate cancer and can be used to measure disease activity.
In around half of the men, PSA levels fell by at least 50 per cent, while three-quarters of participants also had a drop in the number of tumour cells circulating in their blood.
Three years after the start of the trial, five of the patients were still taking abiraterone and benefitting from the treatment.
New phase II data on abiraterone was reported this week in the Journal of Clinical Oncology from the researchers at the Royal Marsden.
Standard chemotherapy with docetaxel (Taxotere) improves survival by 2 to 3 months, so if the 6 months seen with abiraterone is repeated in a phase III trial, Johnson and Johnson (J&J) and Cougar could well have an approvable drug on their hands. The other benefit is that the side effect profile is much milder than chemotherapy, which can cause severe myelosuppression in the majority of patients receiving it.
It should be noted that these are advanced patients who have received already several hormonal therapies. The data from this trial will likely provide impetus for larger scale phase III trials, which could be used to seek regulatory approval from the US and EU authorities.
It is, however, obvious that the investigators are unsure yet what role and where abiraterone will eventually be used in the treatment paradigm, but traditional research approaches require that trials investigate advanced disease and then more up the continuum as more data and experience with the treatment is gained.
Of course, there is no guarantee that phase III trials will mirror promising phase II results, especially in the cancer arena, but now, it's nice to report on positive data after a bad run of disappointing trials in oncology of late.
Source: JCO (Abstract)
Reid, A., Attard, G., Danila, D., Oommen, N., Olmos, D., Fong, P., Molife, L., Hunt, J., Messiou, C., Parker, C., Dearnaley, D., Swennenhuis, J., Terstappen, L., Lee, G., Kheoh, T., Molina, A., Ryan, C., Small, E., Scher, H., & de Bono, J. (2010). Significant and Sustained Antitumor Activity in Post-Docetaxel, Castration-Resistant Prostate Cancer With the CYP17 Inhibitor Abiraterone Acetate Journal of Clinical Oncology DOI: 10.1200/JCO.2009.24.6819