A common current therapeutic approach to APL uses oral ATRA and chemotherapy in induction and consolidation. This approach has significantly improved survival in newly diagnosed APL patients. However, approximately 30% of patients relapse. Recently, an approach involving the combination of oral ATRA and arsenic trioxide has been tested. The prognosis for relapsed patients is very poor. This study seeks to investigate NRX 195183 monotherapy in patients who have failed or are resistant to or are intolerant of any prior therapy.