The Committee for Medical Products for Human Use (CHMP) of the European Medicines Agency (EMA) has granted a positive opinion recommending the approval of abiraterone acetate (Zytiga?, Janssen-Cilag International NV) for the treatment of metastatic castration resistant prostate cancer. The approval was based on the accelerated regulatory review procedure.

Abiraterone is a novel, once-daily, oral, androgen biosynthesis inhibitor developed for the treatment of prostate cancer and works by inhibiting the CYP17 enzyme complex, which is required for the production of androgens. The proposed indication is the treatment – with prednisone or prednisolone – of metastatic castration resistant prostate cancer in adult men whose disease has progressed on or after a docetaxel-based chemotherapy regimen. [1]

Prostate cancer
Metastatic castration resistant prostate cancer occurs when cancer has metastasised beyond the prostate and disease progresses despite serum testosterone (androgens)below castrate levels. In 2008, an estimated 370,000 new cases of prostate cancer were diagnosed in Europe, and nearly 90,000 men died from the disease. [2] Androgens are hormones that promote the development and maintenance of sex characteristics. However, in prostate cancer androgens can help fuel the tumour’s growth. Androgen production primarily occurs in the testes and adrenal glands; in men with prostate cancer, the tumour tissue is an additional source of androgens.

The CHMP is the committee responsible for the scientific assessment of products seeking centralised marketing authorisation throughout the European Union. The CHMP’s positive opinion is now referred for approval to the European Commission. Janssen anticipates receiving the regulatory decision from the Commission in the third quarter of 2011. The CHMP positive opinion is based on data from the COU-AA-301 study, a pivotal Phase III randomised, double-blind, placebo-controlled clinical trial. The study was conducted in 147 centres in 13 countries and evaluated whether abiraterone in combination with prednisone or prednisolone, improved overall survival in patients with metastatic castration resistant prostate cancer whose disease had progressed following chemotherapy.[3]

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Patients with metastatic castration resistant prostate cancer previously treated with docetaxel (N=1,195) were randomly assigned 2:1 to receive abiraterone acetate (1000 mg once daily) plus prednisone/prednisolone (5 mg twice daily) (N=797), or placebo plus prednisone/prednisolone (N=398). The primary endpoint was overall survival. The secondary end points included PSA response rate, time to PSA progression, and progression-free survival on the basis of radiographic findings.[3]

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Overal survival
After a median follow-up of 12.8 months, the study demonstrated that abiraterone in combination with prednisone or prednisolone, improved overall survival (OS) in patients with metastatic castration resistant prostate cancer whose disease had progressed following chemotherapy.[3] Median overall survival for the group receiving abiraterone acetate plus prednisone/prednisolone was 14.8 months vs. 10.9 months for placebo plus prednisone/prednisolone. Treatment with abiraterone acetate also resulted in a 35.4 percent reduction in the risk of death (HR=0.65; 95 percent CI: 0.54, 0.77; p<0.001) compared with placebo.[3]

Un-blinding
In August 2010 the Independent Data Monitoring Committee recommended un-blinding the study after a pre-specified interim analysis demonstrated a significant improvement in overall survival. In December 2010 the marketing authorisation application was submitted to the European Medicines Agency, with the procedure starting in January 2011. Key results from study COU-AA-301 were published in the New England Journal of Medicine in May 2011.[3]

FDA approval
In April 2011 abiraterone was approved in the US by the Food and Drug Administration (FDA) for use in combination with prednisone for the treatment of patients with metastatic castration-resistant prostate cancer (CRPC) who have received prior chemotherapy containing docetaxel.

Availability
“We will continue to work closely with the authorities to ensure abiraterone becomes available as quickly as possible to patients who suffer from metastatic castration resistant prostate cancer that has become resistant to conventional hormone therapies and for whom today there are very few treatment options left,”commented Jane Griffiths, Company Group Chairman, Janssen Europe, Middle-East, Africa.

For more information:
[1] CHMP summary of positive opinion for Zytiga. Last accessed July 21, 2011.
[3] The Globocan Project. Last accessed July 21, 2011.
[3]De Bono JS, Logothetis CJ, Molina A, Fizazi K, North S, et al. Abiraterone and Increased Survival in Metastatic Prostate Cancer. N Engl J Med 2011; 364 (21):1995-2005 May 26, 2011

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