FLEMINGTON, N.J.--(BUSINESS WIRE)--Dec 5, 2012--Arno Therapeutics, Inc. (OTCBB: ARNI), a clinical-stage biopharmaceutical company focused on the development of oncology therapeutics, today announced that researchers have identified a new immunohistochemistry technique for identifying activated progesterone receptors in breast cancer tumors that may be predictive of response to treatment with onapristone, an investigational progestin receptor antagonist being developed by Arno that has demonstrated anti-tumor activity in preclinical and clinical studies. The findings were reported in a poster entitled “Characterization of progesterone receptor biomarker for predicting antiprogestin in human cancers,” presented today at the 35th Annual San Antonio Breast Cancer Symposium.

The poster describes a new technique for identifying the activated form of the progesterone receptor via nuclear morphology that can be done on a routine basis with freshly obtained or paraffin-fixed and paraffin-embedded tissue. The technique is being further refined and tested on a larger cohort of breast and endometrial cancer samples, with correlation to other standard tumor markers and clinical outcomes; these data sets will be presented at a future medical meeting. Additional testing in other malignancies is ongoing. The investigators believe this technique for identifying activated progesterone receptors may allow a method for selecting patients who are most likely to respond to antiprogestins such as onapristone.

Last month at the 24 th European Organization for Research and Treatment of Cancer Symposium on Molecular Targets and Cancer Therapeutics, Arno reported results of preclinical investigations in which cancer cells that express the activated form of the progesterone receptor responded to treatment with onapristone, while cells that did not express the activated form of the progesterone receptor did not respond to onapristone treatment.

Glenn Mattes, president and chief executive officer of Arno Therapeutics, stated, “The continued progress of our research colleagues in describing the predictive value of activated progesterone receptors suggests that we are moving closer to identifying a clinical biomarker that may determine which patients with breast, endometrial and other cancers respond best to treatment with onapristone. This work is very helpful to our efforts to develop a companion diagnostic for onapristone, which is an integral part of our clinical development of onapristone as a potential new cancer therapy.” About Onapristone Onapristone is an anti-progestin hormone blocker that has been shown to have considerable anti-tumor activity in patients with breast cancer. In prior clinical studies, onapristone has demonstrated a 56% objective response rate as a first line “hormone” treatment of breast cancer. Arno has previously reported results of preclinical investigations in which cancer cells that express the activated form of the progesterone receptor responded to treatment with onapristone while cells that did not express the activated form of the progesterone receptor did not respond to onapristone treatment. In connection with the development of onapristone, Arno is also developing a companion diagnostic product to selectively identify patients who express the activated form of the progesterone receptor and would potentially be more likely to benefit from treatment with onapristone. The Company is conducting pre-clinical toxicology studies and manufacturing activities in 2012 and plans to file an investigational new drug application or foreign equivalent in 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 clinical-stage anti-cancer product candidates with unique mechanisms of action. These compounds are in preclinical or clinical testing 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 potential for onapristone to treat APR-positive cancers, the timing, progress and anticipated results of the clinical and regulatory development of onapristone, Arno’s ability to develop a companion diagnostic for onapristone, Arno’s ability to fund the development of onapristone to completion, as well as Arno’s strategy, future operations, outlook, milestones, future financial position, future financial results, plans and objectives. Arno may not actually achieve these plans, intentions or expectations and investors are cautioned 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, 2011 and Quarterly Reports on Form 10-Q for the quarters ended June 30, 2012 and September 30, 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: Arno Therapeutics, Inc.