Antidote-controlled DNA aptamer modulates human factor IXa activity

Thrombosis leads to elevated mortality rates and substantial medical expenses worldwide. Human factor IXa (HFIXa) protease is pivotal in tissue factor (TF)-mediated thrombin generation, and represents a promising target for anticoagulant therapy. We herein isolated novel DNA aptamers that specifically bind to HFIXa through systematic evolution of ligands by exponential enrichment (SELEX) method. We identified two distinct aptamers, seq 5 and seq 11, which demonstrated high binding affinity to HFIXa (K_d = 74.07 ± 2.53 nM, and 4.93 ± 0.15 nM, respectively). Computer software was used for conformational simulation and kinetic analysis of DNA aptamers and HFIXa binding. These aptamers dose-dependently prolonged activated partial thromboplastin time (aPTT) in plasma. We further rationally optimized the aptamers by truncation and site-directed mutation, and generated the truncated forms (Seq 5-1t, Seq 11-1t) and truncated-mutated forms (Seq 5-2tm, Seq 11-2tm). They also showed good anticoagulant effects. The rationally and structurally designed antidotes (seq 5-2b and seq 11-2b) were competitively bound to the DNA aptamers and effectively reversed the anticoagulant effect. This strategy provides DNA aptamer drug-antidote pair with effective anticoagulation and rapid reversal, developing advanced therapies by safe, regulatable aptamer drug-antidote pair.