 This 1-week study will test the safety and dosing of an anticoagulation system called REG1 that is designed to improve control of blood thinning. Patients with heart attack and other conditions require treatment with an anticoagulant blood thinner to prevent the formation of blood clots. However, anticoagulation therapy can increase the risk of bleeding. The REG1 system is designed to minimize this risk. One part of the system stops the activity of factor IX a protein that helps blood clot while the other part of the system the antidote inactivates the drug and stops the thinning process. This study will examine in normal healthy subjects how the REG1 system works in the body and how it leaves the body. 