FXIIa-IN-5 (Compound 4J) is an orally effective selective inhibitor of factor XIIa (FXIIa), with an IC50 of 21 nM. It inhibits the intrinsic coagulation pathway and demonstrates anti-inflammatory and antithrombotic activities in a Carrageenan-induced thrombosis model in mice. FXIIa-IN-5 exhibits moderate pharmacokinetic properties and mild toxicity at a dosage of 100 mg/kg.