Vmx-C001 Prevents Rivaroxaban-Induced Bleeding in a Liver Injury Model in Cynomolgus Monkeys

Background: VMX-C001 is an engineered recombinant human coagulation factor X (FX) that is insensitive to inhibition by FXa direct oral anticoagulants (FXa-DOACs). Upon administration it bypasses the effect of FXa DOACs and rapidly restores coagulation. It is under development for reversal of FXa DOACs in patients with serious bleeding or requiring urgent surgery. VMX-C001 has previously been shown to be safe and well tolerated in a FIH study in subjects treated with apixaban and rivaroxaban. To date, efficacy of VMX-C001 was shown in coagulation assays, such as thrombin generation (TG), dilute prothrombin time (dPT) and dilute Russels’ Viper Venom time (dRVVT). An injury-bleeding model was developed in cynomolgus monkeys to study the effects of VMX-C001 on FXa-DOAC induced bleeding in vivo.

Aims: To study the effects of VMX-C001, either alone or in combination with a FXa-DOAC (rivaroxaban), on post-injury bleeding in monkeys, and determine how coagulation assays correlate with bleeding.

Methods: Male monkeys were anesthetized, the liver was exposed, and a 4 mm diameter/2 mm depth injury was made in the liver using a punch biopsy tool. Post-injury bleeding time was measured up to a maximum of 1200 seconds and blood loss was determined by weighing gauze used to absorb blood from the injury. All animals were treated similarly at baseline. To assess the efficacy of VMX-C001 to bypass the effects of rivaroxaban, post-injury bleeding outcomes were measured in monkeys (N = 24) before and after rivaroxaban administration (IV bolus followed by continuous infusion) alone, and then after VMX-C001 IV bolus administration (1.3 mg/kg; N =7 or 0.9 mg/kg; N =7) or placebo (N = 10). The surgery team and assessors were blinded to the treatment (VMX-C001 or placebo). Post-injury bleeding time and blood loss were assessed at baseline and 20 minutes after each dose. To study the effect of VMX-C001 alone on bleeding outcome monkeys (N = 10) received two IV bolus doses of VMX-C001 (1.3 mg/kg; N = 6 or 3.0 mg/kg; N = 4), 20 minutes apart and bleeding was assessed before and after the first dose, and then after the second dose. Blood samples were taken to evaluate clotting (PT, aPTT, dPT, dRVVT and TG) and VMX-C001 and/or rivaroxaban plasma level.

Results: In animals pre-treated with rivaroxaban, clotting assays were prolonged: PT from 9.2±0.6 to 21.7±8.8 sec; aPTT from 23.8±2.4 to 42.0±12.6 sec. VMX-C001 administration shortened the PT in both dose groups (1.3 mg/kg: 14.2±1.2 and 0.9 mg/kg: 16.4±3.3 sec) but the aPTT remained prolonged (1.3 mg/kg: 52.0±6.6 and 0.9 mg/kg: 56.6±6.7 sec). At the time of VMX-C001 administration mean rivaroxaban plasma levels were 554 ng/ml (range 300 – 1732) in the 1.3 mg/kg dose group and 760 ng/ml (range 222 – 1961) in the 0.9 mg/kg group. Mean VMX-C001 plasma levels were 28.4 and 19.4 µg/ml in the 1.3 and 0.9 mg/kg dose groups post administration. At baseline (N = 34), median bleeding time was 144 sec (range 80 – 814) and median blood loss was 2.0 gr (range 0.3 – 9.4). Rivaroxaban increased bleeding time to the maximum of 1200 seconds in 19 out of 24 animals and median blood loss was 14.1 gr (range 2.0 – 56.6). Administration of VMX-C001 reversed the effect of rivaroxaban on bleeding time in both dose groups (1.3 mg/kg: 201 sec, range 123 – 926; 0.9 mg/kg: 239 sec, range 167 – 1133). Additionally, post-injury blood loss was reduced to baseline values in both groups (1.3 mg/kg: 2.3 gr, range 0.5 – 5.3 and 0.9 mg/kg: 2.4 gr, range 1.3 – 8.9). In contrast, bleeding time and blood loss (1200 sec and 21.4 gr, range 10.1 – 76.1) remained high in the placebo group. In monkeys administered VMX-C001 alone, PT marginally increased to 10.5±0.4 sec, but aPTT increased dose-dependently to 36.4±1.4 and 43.8±7.8 sec after two doses of either 1.3 mg/kg or 3.0 mg/kg. After the 2^nd dose, mean VMX-C001 plasma levels were 51.0 and 97.4 µg/ml in either group. The increases in PT and aPTT were not associated with altered bleeding outcomes post-injury after dosing twice with 1.3 mg/kg (151 sec, range 91 – 755; 2.1 gr, range 0.2 – 5.8) or 3.0 mg/kg (87 sec, range 69 – 205; 1.7 gr, range 0.8 – 2.7).

Conclusion(s): VMX-C001 completely reverses rivaroxaban-induced increases in bleeding time and blood loss, but leaves the aPTT prolonged. VMX-C001 alone has no impact on bleeding outcomes, despite prolonging the aPTT. Changes in PT/aPTT appear not to predict the effect of VMX-C001 on bleeding. Results on coagulation assays TG, dRVVT and dPT are pending and will be communicated at the congress.