Development of an RNA-based anticoagulant and antidote for precise on/off coagulation control during cardiovascular procedures

PROJECT SUMMARY Each year, approximately one-third of all hospitalized patients in the US (corresponding to about 12 million Americans) receive unfractionated heparin (UFH) to prevent clotting during surgical and invasive medical procedures, such as open-heart surgery and transcatheter heart valve replacement, and to prevent postoperative clotting issues, such as deep vein thrombosis, and major ischemic events, such as pulmonary embolism, heart attack, and stroke. UFH is a fast-acting, reversible, and inexpensive anticoagulant drug that indirectly inhibits several clotting factors, including thrombin and Xa. However, UFH is associated with serious acute side effects, including hypersensitivity reactions. The non-linear dose response to UFH and a high degree of patient-to-patient and batch-to-batch variability lead to medication errors related to improper dosing, and these errors are among the most common and serious in clinical practice. An estimated 1-5% of patients who receive UFH experience an immune response known as heparin-induced thrombocytopenia (HIT), which is considered life threatening or results in death in 20-30% of affected patients. Additionally, up to 26% of cardiac surgery patients experience “heparin resistance,” where achieving therapeutic anticoagulation requires excessive doses of UFH. As with any anticoagulant, treatment with UFH carries the risk of excessive bleeding, which can be fatal. UFH is reversed by protamine, which is also associated with serious side effects, including anaphylaxis and toxicity. Accurate determination of the dosing ratio of protamine to UFH is challenging, putting patients at risk for protamine overdose. In the context of medical procedures that require precise (i.e., immediate and titratable) hemostatic control, such as transcatheter heart valve replacement, these shortcomings are particularly challenging. Thus, there is a recognized, unmet medical need for new anticoagulant/reversal agent combinations that are safe and fast acting with a predictable dose response to enable more precise hemostatic control during medical procedures. Helixomer, Inc. is developing a novel polynucleotide-based anticoagulant/antidote combination for intravenous anticoagulation. In vitro and in vivo data have demonstrated that Helixomer’s anticoagulant drug, Hex01, and its antidote, Hex02, are highly specific and fast acting, with clear, predictable dose responses. Hex01 specifically binds to and directly inhibits thrombin, the enzyme responsible for fibrin deposition and clot formation. Hex02 base-pairs with and deactivates Hex01, reversing the anticoagulant effect by releasing thrombin. In this Direct-to-Phase II SBIR project, Helixomer will advance the preclinical development of Hex01 and Hex02 by i) validating bioanalytical assays for Hex01 and Hex02 in plasma to support preclinical development, ii) establishing scale-up manufacturing methods for Hex01, iii) determining a dosing strategy for Hex01 and Hex02 in a porcine large-animal model, and iv) defining safety and toxicity profiles for Hex01 and Hex02 and identifying the maximum tolerated dose through non-GLP dose range finding studies in rats and dogs. Successful completion of these critical preclinical studies will support subsequent pivotal GLP toxicology studies and IND submission.