The purpose of this study is to study the safety, cellular mechanism and effectiveness of CNI-1493 in treatment of psoriasis. While the exact cause of psoriasis is unknown, it is believed to involve white blood cells called lymphocytes which become activated in the skin. It is believed that these activated cells both increase tissue replication and produce inflammation within the skin. CNI-1493 is designed to block the activation of these lymphocytes. Because the CNI-1493 targets the specific cells which are involved in the symptoms of psoriasis, it may be a therapeutic advance in treatment of the disease. The purpose of this study is to test the safety, cellular mechanism and clinical activity of CNI-1493 in patients with active, moderate to sever psoriasis vulgaris.