Background: Predictable pharmacokinetics allows for subcutaneous injection of enoxaparin once daily. Uncontrolled bleeding after enoxaparin is rare but may occur. The only registered antidote – protamine sulfate has only 60% efficacy and can cause severe complications. We developed heparin-binding copolymer (HBC), a diblock copolymer that reverses intravenously administered heparins and fondaparinux (Kalaska et al., Trans Res, 2016, Kalaska et al., J Pharmacol Exp Ther, 2020).

Aims: We focused on the optimal dosage regimen of HBC for reversing the anticoagulant activity of subcutaneously-administered enoxaparin in healthy mice.

Methods: Male BALB/c mice were subcutaneously injected with enoxaparin (5 mg/kg). After 110 minutes, vehicle (PBS), HBC (6.25 mg/kg or 12.5 mg/kg) or protamine (5 mg/kg or 10 mg/kg) were administered into the tail vein. The blood was collected after 3, 10, 60, 180, 360, and 600 minutes after their administration. Then, the activity of anti-factor Xa and IIa, and blood parameters were measured. All procedures involving animals were approved (Permit Numbers 6/2021) and conducted according to Directive 2010/63/EU. The data were analyzed with GraphPad Prism 6 software using the Mann-Whitney test. P values less than 0.05 were considered significant.

Results: HBC at a lower dose reversed the effect of enoxaparin on anti-factor Xa activity after 3 and 10 minutes, whereas higher dose reversed anti-factor Xa activity, whenever it was increased by enoxaparin (Figure 1). Both doses of HBC completely reversed the effect of enoxaparin on anti-factor IIa activity. Protamine did not reverse anti-factor Xa activity, and only partially reversed anti-factor IIa activity increased by enoxaparin. Safety studies revealed decreased number of blood platelets, and elevated liver enzymes in group treated with HBC at higher dose.

The neutralization of enoxaparin by HBC (6.25 mg/kg and 12.5 mg/kg) or protamine sulfate (5 mg/and 10 mg/kg) in mice 3, 10, 60, 180, 360, and 600 minutes after enoxaparin administration, measured by anti-factor Xa activity.

Conclusions: HBC might be an efficient substitute for protamine sulfate to stop major bleeding that may occur in patients receiving subcutaneously enoxaparin.
Funding: National Science Centre, Poland (2016/21/B/ST5/00837).

« Back to ISTH 2021 Congress

ISTH Congress Abstracts - https://abstracts.isth.org/abstract/heparin-binding-copolymer-completely-reverses-the-anticoagulant-effect-of-subcutaneously-administered-enoxaparin-in-mice/