Arno Therapeutics Reports Activated Progesterone Receptors Predictive of Response to Onapristone

FLEMINGTON, N.J., April 8, 2013 (GLOBE NEWSWIRE) -- Arno Therapeutics, Inc. (OTCQB:ARNI), a clinical stage biopharmaceutical company focused on the development of oncology therapeutics, today announced the presentation of data examining onapristone's effect on preclinical models of breast cancer, utilizing a biomarker, which has the potential to identify patients with certain cancers that may best respond to onapristone therapy. The findings were reported in a poster entitled "Antiprogestin drug development: In vitro validation of a potential clinical biomarker," presented today at the American Association for Cancer Research (AACR) Annual Meeting 2013 in Washington, DC.

Onapristone is Arno's investigational progestin receptor antagonist that has demonstrated anti-tumor activity in preclinical and clinical studies of hormone-dependent tumors. In this preclinical study, onapristone showed inhibitory effects in cell lines with activated progesterone receptors (APR). Along with data previously presented at the 2012 San Antonio Breast Cancer Symposium, researchers concluded that the immunohistochemistry (IHC) technique developed to identify activated progesterone receptors in tumors may be applicable in the clinical setting.

"We are continuing to move forward with our plans to develop a companion diagnostic to test patients' tumor samples for APR," said Alexander Zukiwski, Vice President and Chief Medical Officer of Arno, and an author of the study. "Identifying this biomarker brings us one step closer to initiating Phase II clinical trials for onapristone. The results seen thus far indicate that tumors expressing APR may best respond to onapristone. Additionally, as we move forward with planned studies in breast and endometrial cancer, we are continuing to test other cancer samples that may also express APR. "

In the study, researchers examined six human breast cancer and two human endometrial cancer cell lines. Using the novel IHC technique, as well as Western Blotting, investigators determined whether each cell line was positive or negative for activated progesterone receptors. When exposed to onapristone, the cell lines that were positive for APR responded to the treatment while the cells lines not exhibiting APR did not.

Arno Therapeutics plans to initiate Phase I clinical studies in onapristone in the second half of 2013.

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 potential best- or first-in-class products 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 the timing, progress and anticipated results of the clinical development of onapristone, and 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.

CONTACT: The Ruth Group Stephanie Carrington (investors) (646) 536-7017 Arno Therapeutics Glenn Mattes 862-703-7176 Caitlin Cox (media) (646) 536-7033Source:Arno Therapeutics Inc.