 The primary focus of this study is to explore the safety of a range of doses of rNAPc2 in subjects who are managed in hospitals that most typically practice an early invasive strategy catheterization during the index admission. After completion of the ascending dose-ranging part of the trial and review of these data by the Data and Safety Monitoring Board DSMB, the maximum tolerated dose of rNAPc2 will be studied in single-arm, open-label panels approximately 25 subjects each of rNAPc2 with descending doses of unfractionated heparin UFH. 