Reversal of heparin-induced increases in aPTT in the rat by PM102, a novel heparin antagonist

Protamine is the only agent approved to reverse heparin-induced anticoagulation. Due to the significant adverse effects of protamine there is an important need for an alternative agent with an improved safety profile. The pharmacodynamics of PM102, a novel peptide-based heparin antagonist, was evaluated and compared to protamine in a rat model. Rats were dosed with intravenous heparin (50U/kg) and 4min later with protamine (0.25, 0.75mg/kg single intravenous bolus) or PM102 (0.1, 0.3, 1, 3, 30mg/kg single intravenous bolus). Blood samples were collected though 60min for assessment of activated partial thromboplastin time (aPTT) and plasma concentration of PM102. Both doses of protamine markedly lowered the elevated aPTT to baseline values within 1 to 5min after administration. PM102 (0.3-30mg/kg) also rapidly and completely reversed heparin-induced increases in aPTT within 1 to 5min. The effects of PM102 administered as an infusion over 10min also reversed aPTT with similar potency to that observed for bolus administration. The onset of reversal with infusion was delayed relative to the same total dose given as a bolus; however, the maximum effect was similar. PM102 rapidly (T(max) 1-2.6min) appeared in plasma after dosing. Concentrations of PM102 generally declined rapidly after reaching T(max) with a mean T(1/2) of 4 to 31min. PM102 is a novel synthetic peptide that effectively reverses the anticoagulant effect of heparin. It's utility as a bolus injection as well as infusion, its rapid efficacy and its rapid clearance make this an ideal candidate for clinical development.