Abiraterone - Clinical Studies

Clinical Studies

A phase III trial in subjects previously treated with docetaxel started in 2008. A placebo-controlled randomised phase III clinical trial in patients with castration-refractory prostate cancer who are chemotherapy-naive opened to accrual in April 2009.

In September 2010, an independent panel found that the interim results of the phase III clinical trial in previously treated docetaxel patients were so successful that it would have been unethical to keep half the trial participants on placebo, and all patients began receiving the drug. Overall survival was increased by 3.9 months according to this trial (14.8 months versus 10.9 months for placebo). It was approved by the FDA in April 2011.

The first clinical studies were run in 2004. A more recent study in patients who had not received chemotherapy reported in 2007 that abiraterone acetate induced decline in prostate specific antigen (PSA) in up to 70% of patients as well as radiological shrinkage of tumors, symptom improvement, normalisation of lactate dehydrogenase. However others cautioned in 2008 that it was too early to know whether abiraterone treatment will have long term benefit.

Results of two phase II trials indicate that abiraterone may reduce prostate specific 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. On average, progression-free survival (PFS) was prolonged by 161 days in patients which had been treated with chemotherapy, and by 236 days in chemotherapy naive patients. Phase II clinical trials of abiraterone's effectiveness in patients who have not yet received treatment with chemotherapy (33 patients) found a median time to PSA progression of 48 weeks. Another phase II trial in patients who had failed prior treatment with docetaxel (47 patients) showed a median time to PSA progression of 24 weeks.

A phase I/II clinical trial evaluating abiraterone acetate in advanced breast cancer patients is also underway.

The results of a small study showed that abiraterone eliminated or nearly eliminated tumors in about one-third of men whose disease had not yet spread beyond the prostate gland but was considered likely to do so.

A double-blind phase III randomised controlled trial investigated the use of abiraterone acetate in men with metastatic castration-resistant prostate cancer with no previous chemotherapy. They randomly assigned 1,088 patients to receive abiraterone acetate (1000 mg) plus prednisone (5 mg twice daily) or placebo plus prednisone. The median radiographic progression-free survival was 16.5 months with abiraterone–prednisone and 8.3 months with prednisone alone (hazard ratio (HR) = 0.53; 95% confidence interval (CI), 0.45 to 0.62; P<0.001). After a median follow-up period of 22.2 months, overall survival was improved with abiraterone–prednisone (median not reached, vs. 27.2 months for prednisone alone; HR = 0.75; 95% CI, 0.61 to 0.93; P=0.01).