Compositional variations in porcine mucosal heparins used for the production of low molecular weight heparins. Impact on generic low molecular weight heparin development

Low molecular weight heparins (LMWHs) are made by depolymerization of porcine mucosal heparin (PMH). Although biologic activity of heparins is stated in USP or EP units, there are no specific guidelines on molecular and structural attributes. LMWHs are characterized by anti‐Xa/IIa ratio, molecular weight profile and microchemical structure. Specifications to characterize the starting material such as source verification, contaminants and potential viral load should be defined. Profiling of ten PMHs obtained from various vendors revealed significant differences in molecular weight distribution profile, antithrombin affinity component ratios and protamine titration profile. Additional analysis revealed the presence of aromatic signals and solvent impurities in some products. Bovine specific heparin fragments were found in three of the ten PMHs. Controlled heparinase digestion of these preparations under identical conditions did not produce similar products and revealed distinct fingerprinting that can be used to differentiate these heparins. Such observations underscore the importance of characterizing both crude and finished heparin preparations. The observed variations among generic copies of LMWHs may partly be due to variations in starting material. These results suggest that additional specifications for the raw material should be established including, the molecular and structural profile, serpin affinity (AT and HC‐II). A newly developed Q‐PCR technique to detect contaminants and oligosaccharide profiling should also be considered. Such requirements will assure the quality of generic versions of low molecular weight heparins.