Specific antidotes in development for reversal of novel anticoagulants: a review

In the last decade, several direct oral anticoagulants (DOAC; dabigatran, rivaroxaban, apixaban, edoxaban) have been marketed for prophylaxis and/or treatment of thromboembolism without having specific antidotes available for their reversal. Current management of bleeding associated to DOAC includes the removal of all antithrombotic medications and supportive care. Non-specific procoagulant agents (prothrombin complex concentrates and activated factor VIIa) have been used in case of serious bleeding. Currently, some specific antidotes for the DOAC are under development. Idarucizumab (BI 655075; Boehringer Ingelheim) is a fragment of an antibody (Fab), which is a specific antidote to the oral direct Thrombin Inhibitor dabigatran. Andexanet alfa (r-Antidote, PRT064445; Portola Pharmaceuticals) is a truncated form of enzymatically inactive Factor Xa, which binds and reverses the anticoagulant action of the Factor Xa inhibitors (e.g.: rivaroxaban, apixaban and edoxaban). Aripazine (PER-977, ciraparantag; Perosphere Inc.) is a synthetic small molecule (~500 Da) that reverses oral dabigatran, apixaban, rivaroxaban, as well as subcutaneous fondaparinux and LMWH in vivo. These antidotes could provide an alternative for management of life-threatening bleeding events occurring with the above-mentioned anticoagulants. In addition, the specific antidote anivamersen (RB007; Regado Biosciences Inc.) is an RNA aptamer in clinical development to reverse the anticoagulant effect of the parenteral factor IXa inhibitor pegnivacogin, which is also in development. This anticoagulant-antidote pair may provide an alternative in situations in which a fast onset and offset of anticoagulation is needed, like in patients undergoing cardiac surgery with extracorporeal circulation, as an alternative to the heparin/protamine pair. This patent review includes a description of the pharmacological characteristics of the novel specific antidotes, the available results from completed non-clinical and clinical studies and the description of ongoing clinical trials with the new compounds.