Ciraparantag -d8 tetrahydrochloride diacetate (PER977-d8 tetrahydrochloride diacetate) is the deuterium labeled Ciraparantag. Ciraparantag is a thrombin and factor Xa inhibitor. Ciraparantag is a broad-spectrum reversal agent for anticoagulants, including low-molecular-weight heparin, unfractionated heparin, and certain direct oral anticoagulants. It is reported to antagonize the effects of all coagulants except VKAs and agratroban.