The PREVAIL study was a multinational, double-blind, randomized, placebo-controlled, phase 3 trial of enzalutamide. The study was approved by the independent review board at each participating site and was conducted according to the provisions of the Declaration of Helsinki and the Good Clinical Practice Guidelines of the International Conference on Harmonisation. All patients provided written informed consent before participating in the trial. An independent data and safety monitoring committee reviewed safety data at regular intervals and reviewed the prespecified interim analysis conducted by an independent statistical group at the contract clinical research organization where the study database was held.
The study was designed by prostate-cancer experts and employees of the sponsors, Medivation and Astellas Pharma, which are codeveloping enzalutamide. Investigators at the participating centers entered the data into an electronic data-capture system that was verified for source data by monitors from a separate clinical research organization. The data analyses reported here were conducted by the sponsor and were provided to all the authors, who wrote the manuscript and made the decision to submit the manuscript for publication. These authors assume responsibility for the accuracy of the data and adherence to the study protocol, which is available with the full text of this article at NEJM.org. A professional writer who was paid by the sponsors assisted in the preparation of the manuscript. All the authors and participating institutions have agreements with the sponsors regarding the confidentiality of the data.