Antidote-mediated control of an anticoagulant aptamer in vivo

Abstract

Patient safety and treatment outcome could be improved if physicians could rapidly control the activity of therapeutic agents in their patients. Antidote control is the safest way to regulate drug activity, because unlike rapidly clearing drugs, control of the drug activity is independent of underlying patient physiology and co-morbidities. Until recently, however, there was no general method to discover antidote-controlled drugs. Here we demonstrate that the activity and side effects of a specific class of drugs, called aptamers, can be controlled by matched antidotes in vivo. The drug, an anticoagulant aptamer, systemically induces anticoagulation in pigs and inhibits thrombosis in murine models. The antidote rapidly reverses anticoagulation engendered by the drug, and prevents drug-induced bleeding in surgically challenged animals. These results demonstrate that rationally designed drug-antidote pairs can be generated to provide control over drug activities in animals.

Gene therapy progress and prospects: RNA aptamers

“…The 9.3t aptamer-antidote pair was shown to be efficacious in a porcine systemic anticoagulation model and a murine arterial injury model. 6 Further validation of aptamer-antidote pairs as viable replacements for heparin-protamine therapy was demonstrated in a porcine cardiopulmonary bypass surgery model. 32 As a reduction in thrombin generation and inflammation was observed compared to heparin-protamine therapy, this regimen may be particularly well suitable for patients sensitized to protamine or with heparin-induced thrombocytopenia.…”

“…To retard clearance and improve bioavailability, a cholesterol or polyethylene glycol moiety can be conjugated to one end of the aptamer. 6,7 Still, bioavailability may best be achieved not by making the aptamer drug circulate longer in the system but by increasing its avidity (binding capacity or apparent affinity for its target), which can be realized by multimerizing the aptamers in a controlled fashion. 8 The development of useful therapeutics requires testing in animals before human trials can be carried out, and aptamer development may stall if crossreactivity of the selected human aptamer sequence with the animal model of choice is poor.…”

“…When the antidote was added, the anticoagulating effect of aptamer 9.3t was abolished and clotting parameters returned to normal. 6 (b) An aptamer-'caged' antidote chimera was designed to allow for light-triggered deactivation of a thrombin aptamer, and hence reverse the aptamer's function. 35 …”

A Reversible Aptamer Improves Outcome and Safety in Murine Models of Stroke and Hemorrhage

“…To confirm that the aptamer, selected against human Factor IXa, was able to inhibit the murine Factor IXa activity and effectively anticoagulate mice, we administered a cholesterol modified version of the apamer to mice and performed aPTT and ACT coagulation studies upon blood samples taken from the animals (Rusconi et al, 2002(Rusconi et al, , 2004. The aPTT assay measures deficiencies in the intrinsic as well as common pathways of coagulation, whereas the ACT assay reveals deficiencies in coagulation factors involved in the intrinsic pathway only.…”

“…The factor IXa aptamer has demonstrated efficacy as an anticoagulant agent in mice, pigs, and humans, and in each situation its activity was fully reversed upon administration of its antidote oligonucleotide (Rusconi et al, 2004;Dyke et al, 2006;Nimjee et al, 2006). For these reasons, we tested the Factor IXa aptamer in a murine model of ischemic stroke induced by transient middle cerebral artery occlusion (MCAO) to evaluate the aptamer's efficacy as a therapeutic agent for stroke; additionally, we studied drug safety in a subarachnoid hemorrhage (SAH) model to determine the antidote's ability to improve outcome after aptamer-associated hemorrhage.…”