Abiraterone acetate in chemotherapy-naive mCRPC ? Phase III trial ...

This morning, at the ASCO annual meeting, Dr. Charles Ryan will present the full interim results of COU-AA-302, the randomized, Phase III study of abiraterone acetate in chemotherapy-naive patients with metastatic, castration-resistant prostate cancer (mCRPC).

The abstract of this presentation was placed on line just after midnight Eastern time last night and shows that:

• All patients enrolled had to have either asymptomatic or ?mildly? symptomatic mCRPC and could not have received treatment with any form of chemotherapy.
• The trial enrolled 1,088 patients at 151 centers in 123 different countries.
• Half the patients were randomized to treatment with abiraterone acetate (1,000 mg once daily) + prednisone ( 5 mg twice a day); the other half to a placebo + prednisone (5 mg twice a day).

The detailed results of the trial, based primarily on time to radiographic progression (i.e., an increase in evidence of metastatic tumor load to bone and other organs) are as follows:

• Average (median) follow-up was 22.2 months.
• Median time to radiographic progression-free survival (rPFS) was
  • Not reached in the abiraterone acetate + prednisone arm of the trial
  • 8.3 months in the placebo + prednisone arm of the trial
• Median overall survival was
  • Not reached in the abiraterone acetate + prednisone arm of the trial
  • 27. 2 months in the placebo + prednisone arm of the trial , which is the longest survival period reported to date in any randomized, Phase III, clinical trial of men with mCRPC.
• Median time to onset of pain requiring opiate therapy was
  • Not reached in the abiraterone + prednisone arm of the trial
  • 23.7 months in the placebo + prednisone arm of the trial
• Median time to initiation of chemotherapy was
  • 25.2 months in the abiraterone + prednisone arm of the trial
  • 16.8 months in the placebo + prednisone arm of the trial
• Median time to PSA progression was
  • 11.1 months in the abiraterone + prednisone arm of the trial
  • 5.6 months in the placebo + prednisone arm of the trial
• Grade 3/4 adverse effects reported in the abiraterone acetate + prednisone vs. the placebo + prednisone arms of the trial are:
  • Hypertension, 3.9 vs 3.0 percent
  • Hypokalemia, 2.4 vs 1.9 percent
  • Elevated levels of alanine aminotransferase (ALT), 5.4 vs 0.7 percent
  • Elevatedlevels of aspartate aminotransferase (AST), 3.0 vs 0.9 percent

As previously reported, the Independent Data Monitoring Committee concluded that overall survival,? rPFS, and other secondary endpoints all favored the abiraterone acetate + prednisone arm of the study and unanimously recommended unblinding the study and crossing patients over from placebo + prednisone to abiraterone acetate + prednisone.

Also as previously reported, we do not know (and we will now never know) the size of the true, overall survival benefit resulting from treatment with abiraterone acetate + prednisone compared to a placebo + prednisone in men with metastatic, chemotherapy-naive, castration-resistant prostate cancer.

Some additional information about the results of this study are available in a media release issued by a division of Johnson & Johnson, and some of the information above has been modified since being originally posted to reflect information in that media release.

According to the media release, patients treated with abiraterone acetate + prednisone obtained ?an estimated 33 percent improvement in survival? compared to those treated with a placebo + prednisone. However, it is not clear to The ?New? Prostate Cancer InfoLink exactly how the available data can be used to justify that claim, given the limited amount of data available on overall survival at this point in time. At the time of the recommended unblinding of the trial, only 250 progression events (deaths or radiographic progressions) had occurred in the abiraterone + placebo arm of the study compared to 251 progression events in the placebo + prednisone arm.

The media release states, in addition, that Johnson & Jonson ?plans to submit marketing applications with regulatory authorities to extend the use of [abiraterone acetate] in men with mCRPC who have not received chemotherapy, beginning in the second half of 2012.? This would seem to imply that abiraterone actetate is unlikely to be formally approved for use in the treatment of men with chemotherapy-naive mCRPC before the first few months of 2013.

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Filed under: Drugs in development, Living with Prostate Cancer, Management, Treatment Tagged: | abiraterone, castration-resistant, chemotherapy-na?ve, metastatic, outcome, placebo, survival

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