Background: Recently three biosimilar/generic molecules of enoxaparin (Inhixa®, Gmemaxan® and Thorinane®) have been authorized by the European Medicines Agency (EMA), declared as identical to the reference product Clexane®, showing a good comparability in term of biological activity and chemical properties.

Aims: To compare in vitro anti-FXa activity of Inhixa® and Clexane® on normal plasma samples added with different amount of the two molecules.

Methods: Increasing amount of both LMWH were added to normal plasma pool to reach expected final concentration, ranging from 0 UI/ml up to 3.0 UI/ml, for a total of 8 different dilutions
(0 UI/ml, 0.125 UI/mL, 0.25 UI/mL, 0.5 UI/mL, 1.0 UI/mL, 1.5 UI/mL, 2.0 UI/mL, 3.0 UI/mL). Activated partial thromboplastin time (aPTT) and anti-FXa chromogenic assay were performed in duplicate, within 1 hour after sample preparation. Mean±standard deviation (SD), coefficient of variation (CV%) and linear regression analysis were calculated. Bland Altman method was used to evaluate bias between the two molecules.

Results: Clexane® and Inhixa® anti-Xa and aPTT ratio mean values were 0,84 UI/mL and 0,79 UI/mL and 1,81R and 1,76 R, respectively. Anti-FXa mean CV% between the two molecules was 5.45%, showing a costant small, but not significant, underestimation of Inhixa®. Bias between Clexane® and Inhixa® for anti-FXa assay and aPTT were 7,7% and 2,3% respectively. Coefficient of correlation (r) was > 0.999, both in the comparison of the two molecules and the expected values.

Conclusions: In vitro anti-FXa activity of Clexane® and Inhixa® showed very good correlations with a small underestimation of Inhixa®, lower than anti-FXa intra/inter assay variability. Limits are represented by the “in vitro” evaluation that cannot give any information respect “in vivo” pharmacokinetic, pharmakodynamic, clinical efficacy, safety and collateral effect as immunogenic reactivity. A strict pharmacovigilance should be recommended and anti-FXa monitoring, at least in particular clinical settings, should be advised.

[Tab1. Comparison between anti-FXa activity, aPTT and expected results, using the two molecules *Upper limit of detection]

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/biosimilar-enoxaparin-sodium-inhixa-compared-with-clexane-an-in-vitro-study/