Arno Therapeutics Reports Findings Of New Diagnostic Technique The Potential To Identify Patients With Cancer Who May Respond To Treatment With Onapristone

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.”