Arno Therapeutics, Inc. announced that it has received authorization from the Medicines and Healthcare products Regulatory Authority (MHRA) to begin enrolling patients in the United Kingdom in the second stage of its Phase I/II clinical trial evaluating lead compound onapristone in men with advanced castration-resistant prostate cancer (CRPC). An independent data review committee has determined the recommended Phase II dose of single agent onapristone to be 50mg extended release tablets, taken twice daily. The second stage protocol has been modified to evaluate onapristone in combination with abiraterone (Zytiga®) in patients with CRPC that expresses the progesterone receptor (PR) or the T878A androgen receptor (AR) mutation.

The AR T878 receptor mutation has been demonstrated to bind progesterone. The second stage of the study also includes a Phase II cohort of patients with PR-positive CRPC who will receive single agent onapristone. The ongoing, open-label Phase I/II study is currently enrolling patients and is designed to evaluate the safety of onapristone in the selected patient population, determine the recommended Phase II dose and assess the potential benefits of single-agent onapristone and the combination of onapristone with abiraterone.

This multi-site trial is being conducted at three centers in the United Kingdom and is expected to enroll a total of approximately 75 patients.