Arno Therapeutics Data Supports Further Evaluation of Onapristone in Prostate Cancer

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FLEMINGTON, N.J., Oct. 29, 2013 (GLOBE NEWSWIRE) -- Arno Therapeutics, Inc. (OTCQB:ARNI), a clinical stage biopharmaceutical company focused on the development of oncology therapeutics, today announced data from a preclinical study supporting further evaluation of its lead compound onapristone as a potential treatment for castration-resistant prostate cancer (CRPC). Results were presented during a poster session on Thursday, October 24 and in an oral presentation on Saturday, October 26 at the 20th Annual 2013 Prostate Cancer Foundation (PCF) Scientific Retreat, held October 24-26, 2013 in National Harbor, Md.

This year there will be more than 238,000 estimated new cases and 29,000 deaths from prostate cancer in the United States.i Due to initial steroid hormone-dependence, androgen deprivation is the main treatment for advanced disease. However, despite advances in targeting the androgen receptor (AR) pathway leading to significant survival benefit for patients with CRPC, resistance inevitably emerges. Research has shown that the progesterone receptor (PR) becomes overexpressed during prostate cancer progression on hormonal treatments.ii

Onapristone is an oral, anti-progestin hormone blocker that has been shown to have considerable anti-tumor activity in breast cancer. Onapristone appears to have a unique ability to block the activated progesterone receptor (APR), which is believed to be a mechanism that may inhibit the growth of breast, endometrial and other tumors. The APR has the potential to function as a biomarker of anti-progestin activity.

"Overall, these data suggest that the progesterone receptor is present and is potentially active in a subset of castrate-resistant prostate cancers tumors, further supporting the activated form of progesterone receptor as a target for treatment with an anti-progestin like onapristone," said Alex Zukiwski, Chief Medical Officer of Arno Therapeutics and the lead author of the poster. "Prostate cancer is the most frequently diagnosed cancer in men and we plan to evaluate onapristone as a potential personalized therapy for patients in this population who will most likely benefit."

Title: Investigation of the activated form of the progesterone receptor (APR) in castrate-resistant prostate cancer

Authors: Alex Zukiwski, Jacques Bosq, Erard M. Gilles, Arie Belldegrun

As an exploratory analysis of activated androgen receptor (AR), the preclinical study evaluated five CRPC specimens processed with standard immunohistochemistry (IHC) techniques to determine the PR sub-nuclear distribution. APR positive was defined as any tumor with more than 5 percent APR cells (shown as aggregate or foci pattern). The study aimed to detect activated PR in archived castrate-resistant prostate cancers and determine the proportion of cases with activated PR, which would have the potential to respond to anti-progestins.

The analysis illustrated that the activated form of the AR subnuclear distribution pattern was observed. In the initial series of CRPC specimens examined, four were AR positive and two had the aggregated pattern consistent with the activated form of the AR. PR was expressed in three of the five CRPC tumors tested to date and activated PR was detected in two of the five CRPC tumors.

These data suggest that PR is present and is potentially active in a subset of castrate-resistant prostate cancers tumors. In such cases, investigation of an anti-progestin treatment, such as onapristone, is warranted as it could inhibit tumor PR activity to disrupt any PR-driven proliferation. The findings suggest that activated PR detection in prostate cancer is potentially valuable to identify patients who may benefit from anti-progestin treatment.

To investigate onapristone in this patient population, Arno is planning a Phase I study in male patients with androgen-independent prostate cancer which has progressed on either abiraterone or enzalutamide, to determine the safety profile and the recommended dose for further study and evaluate preliminary efficacy in PR-positive and activated PR-positive CRPC.

Glenn Mattes, President and Chief Executive Officer of Arno Therapeutics, said, "We are encouraged by these findings as they further support the evaluation of onapristone as a potentially effective hormone treatment in both men's and women's cancers. Data we have presented to date collectively point to the significance of the role of anti-progestins and using APR as a biomarker in solid tumors. To build upon these results, we are planning a Phase I trial to investigate onapristone in men with castrate resistant prostate cancer."

About Arno Therapeutics

Arno Therapeutics is a clinical stage biopharmaceutical company developing innovative products for the treatment of cancer. Arno has exclusive worldwide rights to develop and market three innovative anti-cancer product candidates. These compounds are in clinical or preclinical development as product candidates to treat hematologic malignancies and solid tumors. For more information about the company, please visit

Forward-Looking Statements

This press release contains forward-looking statements that involve substantial risks and uncertainties. These statements are often, but not always, made through the use of words or phrases such as "anticipates," "expects," "plans," "believes," "intends," and similar words or phrases. These forward-looking statements include, without limitation, statements regarding Arno's belief about the ability of onapristone to treat prostate and other cancers, statements regarding Arno's plans to initiate clinical trials of onapristone in men with prostate cancer, statements regarding the timing, progress and anticipated results of the clinical development of onapristone, as well as statements regarding Arno's strategy, future operations, outlook, milestones, future financial position, future financial results, plans and objectives. We may not actually achieve these plans, intentions or expectations and Arno cautions investors not to place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. Various important factors could cause actual results or events to differ materially from the forward-looking statements that we make. Such factors include, among others, risks that the results of clinical trials will not support our claims or beliefs concerning the effectiveness of onapristone or any of our other product candidates, our ability to finance the development of our product candidates, regulatory risks, and our reliance on third party researchers and other collaborators. Additional risks are described in the company's Annual Report on Form 10-K for the year ended December 31, 2012. Arno is providing this information as of the date of this press release and does not undertake any obligation to update any forward-looking statements as a result of new information, future events or otherwise.

i American Cancer Society. Cancer Facts & Figures 2013. Available at:

ii Bonkhoff 2001, Lange 2007.

CONTACT: The Ruth Group Stephanie Carrington (investors) (646) 536-7017 Kirsten Thomas (media) (646) 536-7014 Arno Therapeutics Glenn Mattes (862) 703-7176

Source:Arno Therapeutics Inc.