Comparative Studies On Branded Enoxaparin and a US Generic Version of Enoxaparin.

Low molecular weight heparins (LMWHs) are complex biologic drugs whose heterogeneity in saccharide chain length and in the composition (sulfate, acetyl), content, and location of functional groups can impact their multiple biologic activities. Enoxaparin (Lovenox®) is validated for multiple indications and is the most widely used LMWH in the US. Several generic versions of enoxaparin are currently available in the US. We undertook this study to compare the activity profile of branded and a generic enoxaparin.

Five batches each of branded (B; Sanofi-aventis; Bridgewater, NJ) and generic (G; Sandoz US; Princeton, NJ) enoxaparin were studied. Drugs were purchased through hospital pharmacies as pre-filled syringes containing 40 mg drug. The molecular weight profile of each batch of LMWH was determined using HPLC. To analyze in vitro activities, LMWHs were supplemented to normal human plasma and assessed using amidolytic anti-FXa and anti-FIIa, fibrinokinetic, and thrombin generation assays. Human whole blood was supplemented with LMWHs and the dynamic blood coagulation process was analyzed by thrombelastography (TEG). Whole blood flow cytometry was used to assess the ability of the LMWHs to inhibit tissue factor (TF)-induced platelet activation and lipopolysaccharide (LPS)-induced neutrophil activation. To assess the in vivo effect of the LMWHs, primates treated subcutaneously with a dose of 1 mg/kg LMWH had blood samples drawn pre-treatment and at 4, 6, 12 and 24 hours. Ex vivo pharmacodynamic activities of TFPI release, TAFI inhibition, and thrombin generation inhibition were evaluated.

Molecular weight parameters and IC₅₀ values for FXa and FIIa inhibition by branded and generic enoxaparin were comparable. In the in vitro thrombin generation and fibrinokinetic assays, branded enoxaparin exhibited a more potent anticoagulant effect demonstrating slower clot formation with a weaker final clot structure (p=0.01) than generic enoxaparin. Although both the branded and generic enoxaparin produced a concentration-dependent anticoagulant effect in the TEG, there was greater degree of variability for the generic product between blood donors and between batches resulting in a less predictable linear response as drug concentration increased. When the increase in TEG R-time was plotted vs. concentration, branded enoxaparin showed a stronger anticoagulant effect (p=0.05). A concentration-dependent reduction in TF-induced platelet P-selectin expression was observed with branded and generic enoxaparin producing a similar effect. Incubation of whole blood with LPS resulted in a dramatic increase in neutrophil CD11b expression (MFI: 13.1±2.8 vs. 249.0±42.1) which was reduced by increasing concentrations of LMWH. This effect appeared to be stronger for generic than branded enoxaparin (MFI: 165.2±31.9 vs. 208.9±25.9). In primates treated with branded and generic enoxaparin, anti-FXa activity assessed by AUC 0–24hrs was similar. Anti-FIIa activity, however, was significantly higher in primates treated with generic enoxaparin (135±28 vs. 91±20 (μg*hr)/ml; p=0.023). AUC for thrombin generation inhibition was (B) 932±59 vs. (G) 775±119 %inhibition*hr; p=0.029. AUC for TFPI release was (B) 1101±98 vs. (G) 822±13 (ng/*hr)/ml; p=0.006. AUC for inhibition of TAFI activation was (B) 780±73 vs. 906±69 % inhibition*hr; p=0.023.

This investigation demonstrated a wider variation in anticoagulant response to generic enoxaparin in comparison to branded enoxaparin. This variation was due to the response of the individual subject as well as to the batch of the product. In addition, both in vitro and in vivo/ex vivo activity differences were observed between branded and generic enoxaparin in several parameters relevant to the antithrombotic effect of LMWH. These findings suggest that simple analytical characterization can establish good quality control in manufacturing but may not assure similarity in biological performance between branded and generic enoxaparin. Thus beside the routinely required characterization, inclusion of additional tests for biologic activities and pharmacodynamic profiling of generic products in animal models may provide useful information on the bioequivalence of the generic versions of enoxaparin.

Walenga:Sanofi-Aventis, Paris, France: Research Funding. Jeske:Sanofi-Aventis, Paris, France: Research Funding. Hoppensteadt:Sanofi-Aventis, Paris, France: Research Funding. Cunanan:Sanofi-Aventis, Paris, France: Research Funding. Escalante:Sanofi-Aventis, Paris, France: Research Funding. Khan:Sanofi-Aventis, Paris, France: Research Funding. Bailey:Sanofi-Aventis, Paris, France: Research Funding. Fareed:Sanofi-Aventis, Paris, France: Research Funding. Bakhos:Sanofi-Aventis, Paris, France: Research Funding.