Pegnivacogin results in near complete FIX inhibition in acute coronary syndrome patients: RADAR pharmacokinetic and pharmacodynamic substudy

Aims Establishing factor IX inhibition in patients with acute coronary syndrome/non-ST-elevation myocardial infarction (ACS/NSTEMI), a setting characterized by increased factor IX activity, is critical to investigate the REG1 system in this target population. The REG1 system (Regado Biosciences, Basking Ridge, NJ) consists of pegnivacogin (RB006), an RNA aptamer that directly inhibits factor IXa, and anivamersen (RB007), its complementary control agent. Methods and results RADAR is a Phase 2b study investigating the use of pegnivacogin in patients (n = 800) with ACS undergoing planned early cardiac catheterization. To validate dose selection and stability of anticoagulation throughout the time of cardiac catheterization at an early stage of the clinical trial, 33 patients, 22 of whom had not received recent prior heparin, underwent thorough pharmacokinetic and pharmacodynamic assessment. Fold prolongation of activated partial thromboplastin time (aPTT) was used to impute factor IX inhibition. Pegnivacogin 1 mg/kg rapidly achieved a high pegnivacogin plasma concentration (26.1 +/- 4.6 mu g/mL), prolonged the aPTT (mean aPTT 93.0 +/- 9.5 s), and approached near complete factor IX inhibition (mean fold increase from baseline 2.9 +/- 0.3). These levels remained stable from the time of drug administration through completion of the catheterization. Conclusion Pegnivacogin administered at a weight-adjusted dose of 1 mg/kg consistently achieves a high level of factor IX activity inhibition among patients with ACS and provides stable anticoagulation during cardiac catheterization. These findings support the dose of pegnivacogin selected for the RADAR study.