Arno Therapeutics, Inc. announced promising data supporting the ongoing clinical development program for lead compound onapristone to be presented at the upcoming 2015 American Society of Clinical Oncology Annual Meeting, being held May 29-June 2 in Chicago, IL. Results from Phase 1 study in women with progesterone (PR) positive tumors have been immensely informative and critical to the advancement of onapristone clinical development program. In addition to demonstrating clinical benefit in a group of heavily pre-treated patients, the study demonstrated that Arno's highly purified onapristone extended-release formulation has a very manageable safety profile, providing the recommended dose for the Phase 2 study currently underway.

Additionally, results from the first portion of Phase 1/2 study in men with advanced castration-resistant prostate cancer (CRPC) confirm the very acceptable safety profile of onapristone. An ongoing Phase 2 clinical trial is evaluating the safety and efficacy of onapristone in post-menopausal women with recurrent or metastatic uterine endometrioid cancer that is APR positive. In addition, the trial is evaluating the companion diagnostic, which is being developed to detect APR in patients with endometrioid cancer to identify those patients more likely to respond to onapristone.

The ongoing Phase 2 study is actively recruiting post-menopausal women with recurrent or metastatic uterine endometrioid cancer that is APR positive. At study entry, patients' APR status is determined by immunohistochemistry (IHC) on biopsy with slides stained using a technically-validated procedure and interpreted by trained pathologists. Patients are treated with the recommended Phase 2 dose (RP2D) of 50mg extended-release onapristone twice daily (BID) as determined by the Phase I portion of the trial until progressive disease or intolerability.

The primary endpoint is objective response rate by RECIST 1.1, with secondary endpoints including relationship between extent of APR expression and onapristone activity, safety and tolerability, duration of response, progression-free survival (PFS) and overall survival (OS). The Simon 2-stage design of the Phase 2 study includes 10 patients in the first stage. If two or more patients respond, the study will recruit an additional 19 patients (stage 2) to confirm anti-tumor activity.