PB0536 - Oral Factor XIIa inhibitor KV998086 protects against FeCl3 induced thrombosis in mice.

Background: FXIIa is a component of the intrinsic coagulation pathway which has been implicated as a target for anticoagulants that may prevent thrombosis without affecting hemostasis.

Aims: This study evaluates the effects of the novel oral FXIIa inhibitor KV998086 on FeCl3-induced arterial thrombosis in mice

Methods: Thrombosis was induced in the right carotid artery of male mice by 3.5% FeCl3 patch for 3 minutes. Blood flow was monitored by doppler flow probe (Transonic TS420) for 30 minutes. Time to occlusion (TTO) was determined in wild-type (WT) mice administered with vehicle, KV998086 by subcutaneous osmotic pump (Alzet, 1003D, 5.8mg/kg/d) for 48 hours or KV998086 by oral gavage (45mg/kg) for 14 hours prior to FeCl3 injury and in FXII knockout mice. Activated partial thromboplastin time (aPTT) was assessed using the Ceveron Alpha automated coagulation analyzer (Technoclone) in mouse plasma. Thrombin generation was assessed in human plasma by long chain polyphosphate stimulation with KV998086 added prior to activation.

Results: KV998086 has an IC50 for FXIIa of 7.3 nM, greater than > 1000-fold selectivity compared with a panel of other serine proteases, and oral bioavailability in rats of 78%. In WT mice (n=10), TTO was 5.04±0.24 minutes as compared with FXII knockout mice (n=8) which were protected against occlusion (>30mins, p< 0.001). TTO in mice treated with KV998086 by pump or gavage was 24.4±3.6 (n=8) and 21.1±2.8 minutes (n=8), respectively, compared to WT (p < 0.001). aPTT was prolonged in plasma from FXIIKO mice by 3.7-fold (108±18.9s, n=5) and in plasma from mice administered KV998086 by pump by 1.5-fold (43.3±3.2s, n=14) as compared to WT mice (28.9±1.1s, n=14, p< 0.001). In human plasma, KV998086 provided a dose dependent decrease of thrombin generation initiated by polyphosphate with an IC50=0.3µM.

Conclusion(s): KV998086 is a potent and selective oral FXIIa inhibitor that protects against FeCl3 induced thrombosis in mice.