FDA approval of abiraterone: some interesting notes

We have already noted the FDA’s approval of abiraterone acetate. However, there are some interesting details that are worthy of note.

According to an e-mail from the American Society of Clinical Oncologists to ite members, written on behalf of the U.S. Food & Drug Administration by Dr. Richard Pazdur, who is the director of the Office of Oncology Drug Products, this approval — as one might expect — is based on the results of the randomized, placebo-controlled, multicenter Phase III clinical trial in 1,195 patients whose results were announced in October 2010.

The original analysis (performed when just 552 patient deaths had occurred) demonstrated a statistically significant improvement in overall survival (OS) in patients receiving abiraterone acetate compared to those on the placebo-containing arm (hazard ratio [HR] = 0.646).  The median OS was 14.8 months in the abiraterone + prednisone arm versus 10.9 months in the placebo + prednisone arm.  However, an updated OS analysis, conducted after 775  patients had died, demonstrated a median OS of 15.8 months in the abiraterone + prednisone arm versus 11.2 months in the prednisone + placebo (HR = 0.740) and showing a survival benefit of 4.6 months as compared to the initial survival benefit of 3.9 months.

Dr. Pazdur’s e-mail categorizes adverse events from treatment with abiraterone + predisone into two groups:

  • The most common adverse reactions (occurring in > 5 percent of patients) were joint swelling or discomfort, hypokalemia, edema, muscle discomfort, hot flush, diarrhea, urinary tract infection, cough, hypertension, arrhythmia, urinary frequency, nocturia, dyspepsia and upper respiratory tract infection.
  • The most common adverse drug reactions resulting in drug discontinuation were increased aspartate aminotransferase and/or alanine aminotransferase, urosepsis and cardiac failure (each in < 1 percent of patients taking abiraterone + prednisone).

The web site for branded information about abiraterone acetate (Zytiga™) is at www.zytiga.com and the complete prescribing information is available on the FDA’s web site.

2 Responses

  1. Why is this so expensive … ? Also, when will Canadians have it in Canada?

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