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 www.arnothera.com.

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.