Abiraterone is a drug currently under investigation for use in prostate cancer. It blocks the formation of testosterone by inhibiting CYP17A1 (CYP450c17), an enzyme also known as 17 alpha -hydroxylase/17,20 lyase. This enzyme is involved in the formation of DHEA and androstenedione, which may ultimately be metabolized into testosterone. This drug was initially discovered and developed at the Institute of Cancer Research in London. Cougar Biotechnology is the biotechnology company conducting the research. It has been announced that Cougar will be acquired by Johnson & Johnson in 2009. Subsequent to merger, J&J will conduct trials.
The first study run at the Royal Marsden Hospital, London, in patients who had not received chemotherapy reported that abiraterone acetate induced decline in prostate specific antigen in up to 70% of patients as well as radiological shrinkage of tumors, symptom improvement, normalization of lactate dehydrogenase. However others have cautioned that it is too early to know whether abiraterone treatment will have long term benefit.
Results of two Phase II trials indicate that abiraterone may reduce prostate speciic antigen (PSA) levels, as well as shrink tumors. Many of the 21 men in the Phase II trial reported significant improvements in their quality of life and several were able to stop taking morphine, used to control the pain caused after the cancer spread into their bones.
A Phase III trial is planned for 2008.
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