Comprehensive Identification and Quantitation of Basic Building Blocks for Low-Molecular Weight Heparin

Quality control, safety assessment and preparation approaches of low molecular weight heparin

Low Molecular Weight Heparins (LMWHs) are well-established for use in the prevention and treatment of thrombotic diseases, and as a substitute for unfractionated heparin (UFH) due to their predictable pharmacokinetics and subcutaneous bioavailability. LMWHs are produced by various depolymerization methods from UFH, resulting in heterogeneous compounds with similar biochemical and pharmacological properties. However, the delicate supply chain of UFH and potential contamination from animal sources require new manufacturing approaches for LMWHs. Various LMWH preparation methods are emerging, such as chemical synthesis, enzymatic or chemical depolymerization and chemoenzymatic synthesis. To establish the sameness of active ingredients in both innovator and generic LMWH products, the Food and Drug Administration has implemented a stringent scientific method of equivalence based on physicochemical properties, heparin source material and depolymerization techniques, disaccharide composition and oligosaccharide mapping, biological and biochemical properties, and in vivo pharmacodynamic profiles. In this review, we discuss currently available LMWHs, potential manufacturing methods, and recent progress for manufacturing quality control of these LMWHs.

New insights into the binding of PF4 to long heparin oligosaccharides in ultralarge complexes using mass spectrometry

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious complication caused by heparin drugs. The ultralarge complexes formed by platelet factor 4 (PF4) with heparin or low molecular weight heparins (LMWHs) are important participants in inducing the immune response and HIT.

OBJECTIVES

We aim at characterizing the interaction between PF4 and long-chain heparin oligosaccharides and providing robust analytical methods for the analysis of PF4-heparin complexes.

METHODS

In this work, the characteristics of PF4-enoxaparin complexes after incubation in different molar ratios and concentrations were analyzed by multiple analytical methods, especially liquid chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry with multiple reaction monitoring were developed to qualitatively and quantitatively monitor heparin oligosaccharides and PF4 in HIT-inducing complexes.

RESULTS

The results showed that the largest proportion of ultralarge complexes formed by PF4 and enoxaparin was at a specific molar ratio, ie, a PF4/enoxaparin ratio of 2:1, while the ultralarge complexes contained PF4 tetramer and enoxaparin at a molar ratio of approximately 2:1.

CONCLUSION

A binding model of PF4 and enoxaparin in ultralarge complexes is proposed with one heparin oligosaccharide chain (∼ dp18) bound to 2 PF4 tetramers in different morphologies to form ultralarge complexes, while PF4 tetramer is surrounded by multiple heparin chains in smaller complexes. Our study provides new insights into the structural mechanism of PF4-LMWH interaction, which help to further understand the mechanism of LMWH immunogenicity and develop safer heparin products.

MsPHep: An online application for low molecular weight heparin rapid characterization based on liquid chromatography-tandem mass spectrometry

Low-molecular-weight heparins (LMWHs) are important anticoagulants widely used in clinic. Since they are comprised of complex and heterogenous glycan chains, liquid chromatography-tandem mass spectrometry (LC-MS) is commonly used for structural analysis and quality control of LMWHs to ensure their safety and efficacy. Yet, the structural complexity arising from the parent heparin macromolecules, as well as the different depolymerization methods used for preparing LMWHs, makes processing and assigning the LC-MS data of LWMHs very tedious and challenging. We therefore developed, and here report, an open-source and easy-to-use web application, MsPHep, to facilitate the LMWH analysis based on LC-MS data. MsPHep is compatible with various LMWHs and chromatographic separation methods. With the HepQual function, MsPHep is capable of annotating both the LMWH compound and its isotopic distribution from mass spectra. Moreover, the HepQuant function enables automatic quantification of LMWH compositions without prior knowledge or any database generation. To demonstrate the reliability and system stability of MsPHep, we tested various types of LMWHs that were analyzed with different chromatographic methods coupled to MS. The results show that MsPHep has its own advantages compared to another public tool GlycReSoft for LMWH analysis, and it is available online under an open-source license at https://ngrc-glycan.shinyapps.io/MsPHep.

[Advances in heparin structural analysis by chromatography technologies]

Heparin （Hp） is the most widely used anticoagulant drug in the clinics， with an annual global output of over 10 billion dollars. Hp， a member of the glycosaminoglycans （GAGs）， is prepared from porcine intestinal mucosa via extraction， separation， and purification. Hp is a linear polysaccharide with repeating disaccharide units. Low-molecular-weight heparins （LMWHs） are depolymerized from Hp via chemical or enzymatic degradation. Compared with Hp， LMWHs exhibit less bleeding side effect， milder immunogenicity， and higher bioavailability when injected subcutaneously. In general， Hps， including LMWHs， are high complex drugs with large molecular weights （MWs）， inhomogeneous MW distributions， and structural heterogeneity， including different degrees and locations of sulfonation， and unique residues generated from different production processes. Thus， developing efficient analytical methods to elucidate the structures of Hps and characterize or quantitate their properties is extremely challenging. Unfortunately， this problem limits their quality control， production optimization， clinical safety monitoring， and new applications. Research has constantly sought to elucidate the complicated structures of Hp drugs. Among the structural analysis and quality control methods of Hp currently available， chromatographic methods are the most widely studied and used. However， no literature thoroughly summarizes the specific applications of chromatographic methods in the structural analysis， manufacturing process， and quality control of Hp drugs. This paper systematically organizes and describes recent research progresses of the chromatographic methods used to analyze Hp drugs， including the identification and composition of monosaccharides， disaccharides， oligosaccharides， and polysaccharides. The applications， innovations， and limitations of these chromatographic methods are also summarized in this review. The insights obtained in this study will help production and quality control personnel， as well as drug researchers， obtain a deeper understanding of the complex structures of Hp drugs. This paper also provides a comprehensive reference for the structural analysis and quality control of Hps， proposes ideas for the development of new quality control methods， and lays a strong foundation for the in-depth structural elucidation of Hp drugs.

Commercial Low Molecular Weight Heparins - Patent Ecosystem and Technology Paradigm for Quality Characterization

Heparin is a subject of ever-growing interest for laboratory researchers and pharmaceutical industry. One of the driving factors is its critical life-saving drug status, which during the COVID-19 pandemic has assumed a central role in disease treatment and/or prevention. Apart, heparin is one amongst few drugs enjoying a "demand constant" status. In 2020, heparin market size was valued to US$6.5 bn., and given the ongoing stability in the COVID-19 health crisis, it is expected to reach US$11.43 bn. by 2027 with yearly growth rate momentum (CAGR) of 3.9% during the forecast period (Pepi et al., Mol Cell Proteomics 20:100,025, 2021). As patent is a limited monopoly, every year, many patents on low molecular weight heparin (LMWH; a chemically or enzymatically degraded product of unfractionated heparin) are losing market exclusivity worldwide, inviting the generic/biosimilar drug manufacturers to capture market share with cheaper drug products. By tracking patent expiration, drugs in patent litigation, regulatory setbacks for innovator companies (such as those seeking data exclusivity or patent term extension), or other unexpected events affecting market demand and competition, generics can make investment decisions in manufacturing off-patent LMWH drug products of commercial significance. However, given the US Food and Drug Administration (FDA), European Medicine Agency (EMA), Drug Regulatory Authority of Pakistan (DRAP), and other regulatory authorities scientifically rigorous standards for generic/biosimilar LMWH drug products marketing approval, the market is secured and momentous for drug makers that could demonstrate through scientific and clinical dataset that the generic/biosimilar LMWH drug product is of the same quality and purity as the innovator drug product. This study presents an overview of the patent landscape of commercially available LMWHs and advanced analytical techniques for their structural and biochemical characterization for quality control and quality assurance during manufacturing and post-marketing. The study also covers FDA, EMA, Health Canada, and DRAP's current approaches to evaluating the generic/biosimilar LMWH drug products for quality, safety including immunogenicity, and efficacy.

Saturated tetrasaccharide profile of enoxaparin. An additional piece to the heparin biosynthesis puzzle

Enoxaparin, widely used antithrombotic drug, is a polydisperse glycosaminoglycan with highly microheterogeneous structure dictated by both parent heparin heterogeneity and depolymerization conditions. While the process-related modifications of internal and terminal sequences of enoxaparin have been extensively studied, very little is known about the authentic non-reducing ends (NRE). In the present study a multi-step isolation and thorough structural elucidation by NMR and LC/MS allowed to identify 16 saturated tetramers along with 23 unsaturated ones in the complex enoxaparin tetrasaccharide fraction. Altogether the elucidated structures represent a unique enoxaparin signature, whereas the composition of saturated tetramers provides a structural readout strictly related to the biosynthesis of parent heparin NRE. In particular, both glucuronic and iduronic acids were detected at the NRE of macromolecular heparin. The tetrasaccharides bearing glucosamine at the NRE are most likely associated with the heparanase hydrolytic action. High sulfation degree and 3-O-sulfation are characteristic for both types of NRE.

Quality control and product differentiation of LMWHs marketed in China using 1H NMR spectroscopy and chemometric tools

Low molecular weight heparins (LMWHs) are heterogeneous mixtures of glycosaminoglycan chains composed of mixture of different lengths and substitution patterns. Structural characterization and quality control of LMWHs have always been challenging. The Chinese drug regulatory authorities have been committed to improve the supervision standards of LMWHs to better regulate the quality and safety of LMWHs in current Chinese market. In the present paper, 80 batches of three types LMWHs (dalteparin, enoxaparin and naldroparin) marketed in China from different manufacturers were studied by ¹H NMR experiments and chemometric analysis. The method can be used not only to monitor impurities and contaminants, but also to check the batch-to-batch consistency of each manufacture. Moreover, for the biosimilar LMWHs from different manufactures, they can be differentiated and clustered according to their slightly different structural compositions originated from production process. By using this method, the quality and safety of LMWHs marketed in China were initially assessed.

Molecular Mechanism of the Anti-Inflammatory Action of Heparin

Our objective is to reveal the molecular mechanism of the anti-inflammatory action of low-molecular-weight heparin (LMWH) based on its influence on the activity of two key cytokines, IFNγ and IL-6. The mechanism of heparin binding to IFNγ and IL-6 and the resulting inhibition of their activity were studied by means of extensive molecular-dynamics simulations. The effect of LMWH on IFNγ signalling inside stimulated WISH cells was investigated by measuring its antiproliferative activity and the translocation of phosphorylated STAT1 in the nucleus. We found that LMWH binds with high affinity to IFNγ and is able to fully inhibit the interaction with its cellular receptor. It also influences the biological activity of IL-6 by binding to either IL-6 or IL-6/IL-6Rα, thus preventing the formation of the IL-6/IL-6Rα/gp130 signalling complex. These findings shed light on the molecular mechanism of the anti-inflammatory action of LMWH and underpin its ability to influence favourably conditions characterised by overexpression of these two cytokines. Such conditions are not only associated with autoimmune diseases, but also with inflammatory processes, in particular with COVID-19. Our results put forward heparin as a promising means for the prevention and suppression of severe CRS and encourage further investigations on its applicability as an anti-inflammatory agent.

Investigation of the biological functions of heparan sulfate using a chemoenzymatic synthetic approach

Heparan sulfate (HS) is a highly sulfated polysaccharide playing essential physiological and pathophysiological roles in the animal kingdom. Heparin, a highly sulfated form of HS, is a widely used anticoagulant drug. Isolated from biological sources, both heparin and HS are polysaccharide mixtures with different sugar chain lengths and sulfation patterns. Structural heterogeneity of HS complicates the investigation of HS-related biological activities. The availability of structurally defined HS oligosaccharides is critical in understanding the contribution of saccharide structures to the functions. The chemoenzymatic synthetic approach is emerging as a cost-effective method to synthesize HS oligosaccharides. Structurally defined oligosaccharides are now widely available for biologists. This review summarizes our efforts in using this new synthetic method to develop new anticoagulant therapeutics and discover the role of HS to protect liver damage under pathological conditions. The synthetic method also allows us to prepare reference saccharide standards to improve structural analysis of HS.

Analysis of the Glycosaminoglycan Chains of Proteoglycans

Glycosaminoglycans (GAGs) are heterogeneous, negatively charged, macromolecules that are found in animal tissues. Based on the form of component sugar, GAGs have been categorized into four different families: heparin/heparan sulfate, chondroitin/dermatan sulfate, keratan sulfate, and hyaluronan. GAGs engage in biological pathway regulation through their interaction with protein ligands. Detailed structural information on GAG chains is required to further understanding of GAG-ligand interactions. However, polysaccharide sequencing has lagged behind protein and DNA sequencing due to the non-template-driven biosynthesis of glycans. In this review, we summarize recent progress in the analysis of GAG chains, specifically focusing on techniques related to mass spectroscopy (MS), including separation techniques coupled to MS, tandem MS, and bioinformatics software for MS spectrum interpretation. Progress in the use of other structural analysis tools, such as nuclear magnetic resonance (NMR) and hyphenated techniques, is included to provide a comprehensive perspective.

Coupling Liquid Chromatography and Tandem Mass Spectrometry to Electrophoresis for In-Depth Analysis of Glycosaminoglycan Drugs: Heparin and the Multicomponent Sulodexide

Glycosaminoglycans (GAGs) contribute to the treatment of many human diseases, especially in the field of thrombosis, because of their anticoagulant activity. GAGs interrupt the coagulation process by interacting with multiple coagulation factors through defined sequences within their linear and negatively charged chains, which are not fully elucidated. Numerous methods have been developed to characterize the structure of pharmaceutical GAGs, including intravenously or subcutaneously administered heparin and orally administered sulodexide. However, most currently available methods only focus on the oligosaccharide portion or analyze the whole mixture because longer-chain polysaccharides are extremely difficult to resolve by chromatographic separation. We have established two novel electrophoresis-mass spectrometry methods to provide a panoramic view of the structures of pharmaceutical GAGs. In the first method, an in-gel digestion procedure was developed to recover GAGs from the polyacrylamide gels, while in the second method, a strong anion exchange ultrafiltration procedure was developed to extract multiple GAG species from the agarose gels. Both procedures are compatible with liquid chromatography-tandem mass spectrometry, and structural information, such as disaccharide composition and chain length, can be revealed for each GAG fraction. The applications of these two methods on analysis of two different GAG drugs, heparin and sulodexide, were demonstrated. The current study offers the first robust tool to directly elucidate the structure of larger GAG chains with more biological importance rather than obtaining a vague picture of all chains as a mixture, which is fundamental for better understanding the structure-activity relationship and quality control of the GAG drugs.

Developments in Mass Spectrometry for Glycosaminoglycan Analysis: A Review

This review covers recent developments in glycosaminoglycan (GAG) analysis via mass spectrometry (MS). GAGs participate in a variety of biological functions, including cellular communication, wound healing, and anticoagulation, and are important targets for structural characterization. GAGs exhibit a diverse range of structural features due to the variety of O- and N-sulfation modifications and uronic acid C-5 epimerization that can occur, making their analysis a challenging target. Mass spectrometry approaches to the structure assignment of GAGs have been widely investigated, and new methodologies remain the subject of development. Advances in sample preparation, tandem MS techniques (MS/MS), online separations, and automated analysis software have advanced the field of GAG analysis. These recent developments have led to remarkable improvements in the precision and time efficiency for the structural characterization of GAGs.

Specific Non-Reducing Ends in Heparins from Different Animal Origins: Building Blocks Analysis Using Reductive Amination Tagging by Sulfanilic Acid

Heparins are linear sulfated polysaccharides widely used as anticoagulant drugs. Their nonreducing-end (NRE) has been little investigated due to challenges in their characterization, but is known to be partly generated by enzymatic cleavage with heparanases, resulting in N-sulfated glucosamines at the NRE. Uronic NRE (specifically glucuronic acids) have been isolated from porcine heparin, with GlcA-GlcNS,3S,6S identified as a porcine-specific NRE marker. To further characterize NRE in heparinoids, a building block analysis involving exhaustive heparinase digestion and subsequent reductive amination with sulfanilic acid was performed. This study describes a new method for identifying heparin classical building blocks and novel NRE building blocks using strong anion exchange chromatography on AS11 columns for the assay, and ion-pair liquid chromatography-mass spectrometry for building block identification. Porcine, ovine, and bovine intestine heparins were analyzed. Generally, NRE on these three heparins are highly sulfated moieties, particularly with 3-O sulfates, and the observed composition of the NRE is highly dependent on heparin origin. At the highest level of specificity, the isolated marker was only detected in porcine heparin. However, the proportion of glucosamines in the NRE and the proportion of glucuronic/iduronic configurations in the NRE uronic moieties greatly varied between heparin types.

Recent advances in biotechnology for heparin and heparan sulfate analysis

Heparan sulfate (HS) is a class of linear, sulfated, anionic polysaccharides, called glycosaminoglycans (GAGs), which present on the mammalian cell surfaces and extracellular matrix. HS GAGs display a wide range of critical biological functions, particularly in cell signaling. HS is composed of repeating units of 1 → 4 glucosidically linked uronic acid and glucosamine residues. Heparin, a pharmacologically important version of HS, having higher sulfation and a higher content of iduronic acid than HS, is a widely used clinical anticoagulant. However, due to their heterogeneity and complex structure, HS and heparin are very challenging to analyze, limiting biological studies and even resulting in safety concerns in their therapeutic application. Therefore, reliable methods of structural analysis of HS and heparin are critically needed. In addition to the structural analysis of heparin, its concentration in blood needs to be closely monitored to avoid complications such as thrombocytopenia or hemorrhage caused by heparin overdose. This review summarizes the progress in biotechnological approaches in the structural characterization of HS and heparin over the past decade and includes the development of the ultrasensitive approaches for detection and measurement in biological samples.

Systematic analysis of enoxaparins from different sources with online one- and two-dimensional chromatography

Enoxaparin, one of the most important low-molecular-weight heparins (LMWHs), is widely used as a clinical anticoagulant.

Preparation of low molecular weight heparins from bovine and ovine heparins using nitrous acid degradation

Low molecular weight heparins (LMWHs) are important anticoagulant drugs. Nitrous acid degradation is a major approach to produce LMWHs, such as dalteparin. Due to the foreseeable shortage of porcine intestinal mucosa heparin and other potential risks, expansion of other animal tissues for heparin preparation is necessary. Heparins from different tissues differ in structure and bioactivity potency, and these variations may be carried over to the LMWH products. Sophisticated analytical techniques have been applied to compare various versions of dalteparins produced from porcine intestinal, bovine lung and ovine intestinal heparins to elucidate the effects of different animal tissues starting materials and processing conditions on the properties of final dalteparin products. With adjusted depolymerization conditions, versions of dalteparins that qualify under the European Pharmacopeia (EP) specifications were manufactured using non-porcine heparins. Dissimilarities among the three interspecies animal tissue heparin-derived dalteparins regarding fine structures are also disclosed, and their origins are discussed.

Heparin/heparan sulfate analysis by covalently modified reverse polarity capillary zone electrophoresis-mass spectrometry

Reverse polarity capillary zone electrophoresis coupled to negative ion mode mass spectrometry (CZE-MS) is shown to be an effective and sensitive tool for the analysis of glycosaminoglycan mixtures. Covalent modification of the inner wall of the separation capillary with neutral or cationic reagents produces a stable and durable surface that provides reproducible separations. By combining CZE-MS with a cation-coated capillary and a sheath flow interface, a rapid and reliable method has been developed for the analysis of sulfated oligosaccharides from dp4 to dp12. Several different mixtures have been separated and detected by mass spectrometry. The mixtures were selected to test the capability of this approach to resolve subtle differences in structure, such as sulfation position and epimeric variation of the uronic acid. The system was applied to a complex mixture of heparin/heparan sulfate oligosaccharides varying in chain length from dp3 to dp12 and more than 80 molecular compositions were identified by accurate mass measurement.

Quantitative analysis of antithrombin III binding site in low molecular weight heparins by exhausetive heparinases digestion and capillary electrophoresis

The antithrombin III (ATIII)-binding site, which contains a special 3-O-sulfated, N-sulfated glucosamine residue with or without 6-O-sulfation, is mainly responsible for the anticoagulant activity of heparin. Undergoing the chemical depolymerization process, the preservation of the ATIII-binding site in low molecular weight heparins (LMWHs) are varied leading to the fluctuation of the anticoagulant activity. Herein we report a capillary electrophoresis (CE) method in combination with heparinase digestion and affinity chromatography for the measurement of molar percentage of ATIII-binding site of LMWHs. After exhaustively digesting LMWHs with the mixture of heparinase I, II and III, almost all the resulting oligosaccharide building blocks, including the three 3-O-sulfated tetrasaccharides derived from the ATIII-binding site, were resolved by CE separation. The peak area of each building block permits quantification of the molar percentage of the ATIII-binding site. The peaks corresponding to the 3-O-sulfated tetrasaccharides were assigned based on the linear relationship between the electrophoretic mobilities of the oligosaccharides and their charge to mass ratios. The peak assignment was further confirmed by analysis of the high ATIII affinity fractions, which contains much high 3-O-sulfated tetrasaccharides. With the method, the molar percentage of the ATIII-binding site of enoxaparin from different batches and different manufactures were measured and compared. It was demonstrated that the CE method provides more precise data for assessing the anti-FXa activity than that of the biochemical assay method.