Tigris Pharmaceuticals, Inc. announced enrollment of its first patient in a randomized Phase 2 clinical trial of AFP-464 (aminoflavone prodrug) with or without Faslodex(R) (fulvestrant) in estrogen receptor (ER)-positive breast cancer patients. Molecular profiling will be used to pre-screen patients for a biomarker called Aryl Hydrocarbon Receptor (AhR), which has shown to predict sensitivity to AFP-464. It is estimated that approximately 70% of breast cancers are ER-positive. The primary endpoint of the study is to determine the percentage of patients that achieve a Clinical Benefit Response. AFP-464 is a novel anti-cancer agent currently being studied by Tigris Pharmaceuticals in a randomized Phase 2 clinical trial with ER-positive breast cancer patients. AFP-464 is also being studied by the National Cancer Institute ("NCI") under a Cooperative Research and Development Agreement (CRADA). NCI is sponsoring two Phase 1 clinical trials in patients with solid tumors under the CRADA. Pre-clinical studies into AFP-464's mechanism of action have shown that AFP-464 is converted to metabolites, which bind covalently to DNA, resulting in p53 activation and apoptosis. AFP-464 has shown a unique pattern of growth inhibitory activity in the NCI's 60 tumor cell line screen, with breast, ovarian, lung and renal tumor cell lines exhibiting particular sensitivity to the compound. In vivo anti-tumor activity of AFP-464 has been demonstrated in several xenograft studies in mice bearing renal and breast cancer. Pre-clinical studies have shown that tumors (breast, ovarian, pancreatic and renal) with AhR localized in the cytoplasm are very sensitive to AFP-464 while those with AhR localized in the nucleus are more resistant.