Combining NMR Spectroscopy and Chemometrics to Monitor Structural Features of Crude Hep-arin

Quantitative 2D 1H, 13C HSQC NMR Spectroscopy for the Determination of Chondroitin Sulfate and Dermatan Sulfate Content in Danaparoid Sodium

OBJECTIVE

 Danaparoid sodium is a biopolymeric complex drug composed of the most abundant heparan sulfate (HS) followed in descending order by dermatan sulfate (DS) and chondroitin sulfate (CS). This composite nature explains its peculiar antithrombotic and anticoagulant properties and make it particularly advantageous when the risk of heparin-induced thrombocytopenia occurs. A specific control of the danaparoid composition is required by the Ph. Eur. The monograph includes the CS and DS limit contents and describes the method for their quantification through selective enzymatic degradations.

MATERIALS AND METHODS

 In this study, a quantitative two-dimensional nuclear magnetic resonance (NMR) method is proposed as a new method suitable for CS and DS quantification. Statistical comparison of the results provided by the analysis of a series of danaparoid samples with both NMR and enzymatic methods highlights a small systematic difference, likely derived from lyase-resistant sequences bearing oxidized terminals. Some modified structures, whose survival to the enzymatic action was confirmed by mass spectrometry, can be detected and quantified by NMR.

CONCLUSION AND RESULTS

 The proposed NMR method can serve for the determination of DS and CS contents, is an easy-to-apply method with no dependence from enzymes and standards, and provides extensive structural information on the overall glycosaminoglycans mixture.

A Precise qNMR Method for the Rapid Quantification of Lot-to-Lot Variations in Multiple Quality Attributes of Pentosan Polysulfate Sodium

Pentosan polysulfate sodium (PPS) is an orphan drug with anticoagulant activity. PPS is prepared from the chemical processing of xylan extracted from beechwood tree to yield a mixture of 4-6 kDa polysaccharides. The chain is mainly composed of sulfated xylose (Xyl) with branched 4-O-methyl-glucuronate (MGA). During generic drug development, the quality attributes (QAs) including monosaccharide composition, modification, and length need to be comparable to those found in the reference list drug (RLD). However, the range of QA variation of the RLD PPS has not been well characterized. Here, multiple PPS RLD lots were studied using quantitative NMR (qNMR) and diffusion ordered spectroscopy (DOSY) to quantitate the components in the mixture and to probe both inter- and intra-lot precision variability. The DOSY precision assessed using coefficient of variation (CV) was 6%, comparable to PPS inter-lot CV of 5%. The QAs obtained from 1D qNMR were highly precise with a precision CV < 1%. The inter-lot MGA content was 4.8 ± 0.1%, indicating a very consistent botanical raw material source. Other process-related chemical modification including aldehyde at 0.51 ± 0.04%, acetylation at 3.3 ± 0.2% and pyridine at 2.08 ± 0.06%, varied more than MGA content. The study demonstrated that 1D qNMR is a quick and precise method to reveal ranges of variation in multiple attributes of RLD PPS which can be used to assess equivalency with generic formulations. Interestingly, the synthetic process appeared to introduce more variations to the PPS product than the botanical source of the material.

Analysis of Heparin Samples by Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy in the Solid State

Heparin is a polydisperse, heterogeneous polysaccharide of the glycosaminoglycan (GAG) class that has found widespread clinical use as a potent anticoagulant and is classified as an essential medicine by the World Health Organization. The importance of rigorous monitoring and quality control of pharmaceutical heparin was highlighted in 2008, when the existing regulatory procedures failed to identify a life-threatening adulteration of pharmaceutical heparin with oversulfated chondroitin sulfate (OSCS). The subsequent contamination crisis resulted in the exploration of alternative approaches for which the use of multidimensional nuclear magnetic resonance (NMR) spectroscopy techniques and multivariate analysis emerged as the gold standard. This procedure is, however, technically demanding and requires access to expensive equipment. An alternative approach, utilizing attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) combined with multivariate analysis, has been developed. The method described enables the differentiation of diverse GAG samples, the classification of samples of distinct species provenance, and the detection of both established heparin contaminants and alien polysaccharides. This methodology has sensitivity comparable to that of NMR and can facilitate the rapid, cost-effective monitoring and analysis of pharmaceutical heparin. It is therefore suitable for future deployment throughout the supply chain.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Nuclear magnetic resonance spectroscopy as an elegant tool for a complete quality control of crude heparin material

Nuclear magnetic resonance (NMR) spectrometric methods for the quantitative analysis of pure heparin in crude heparin is proposed. For quantification, a two-step routine was developed using a USP heparin reference sample for calibration and benzoic acid as an internal standard. The method was successfully validated for its accuracy, reproducibility, and precision. The methodology was used to analyze 20 authentic porcine heparinoid samples having heparin content between 4.25 w/w % and 64.4 w/w %. The characterization of crude heparin products was further extended to a simultaneous analysis of these common ions: sodium, calcium, acetate and chloride. A significant, linear dependence was found between anticoagulant activity and assayed heparin content for thirteen heparinoids samples, for which reference data were available. A Diffused-ordered NMR experiment (DOSY) can be used for qualitative analysis of specific glycosaminoglycans (GAGs) in heparinoid matrices and, potentially, for quantitative prediction of molecular weight of GAGs. NMR spectrometry therefore represents a unique analytical method suitable for the simultaneous quantitative control of organic and inorganic composition of crude heparin samples (especially heparin content) as well as an estimation of other physical and quality parameters (molecular weight, animal origin and activity).

Variability in the composition of porcine mucosal heparan sulfates

Commercial porcine intestinal mucosal heparan sulfate (HS) is a valuable material for research into its biological functions. As it is usually produced as a side-stream of pharmaceutical heparin manufacture, its chemical composition may vary from batch to batch. We analysed the composition and structure of nine batches of HS from the same manufacturer. Statistical analysis of the disaccharide compositions placed these batches in three categories: group A had high GlcNAc and GlcNS, and low GlcN typical of HS; group B had high GlcN and GlcNS, and low GlcNAc; group C had high di- and trisulfated, and low unsulfated and monosulfated disaccharide repeats. These batches could be placed in the same categories based on their ¹H NMR spectra and molecular weights. Anticoagulant and growth factor binding activities of these HS batches did not fit within these same groups but were related to the proportions of more highly sulfated disaccharide repeats.

A NIR, 1H-NMR, LC-MS and chemometrics pilot study on the origin of carvedilol drug substances: a tool for discovering falsified active pharmaceutical ingredients

Falsification of drugs, entailing the use of drug substances from unknown unapproved suppliers, is one of the main concerns for the quality of medicines. Therefore, traceability of active ingredients represents an effective tool to fight the illegal trade of medicinal products. In this view, the present pilot study explores the profile of carvedilol active ingredients and possible differences related to the origin. Sixteen samples were examined by near-infrared spectroscopy (NIR), proton nuclear magnetic resonance (¹H-NMR spectrometry) and liquid chromatography mass spectrometry (LC-MS) Q-TOF and the data were analysed by principal component analysis (PCA), cluster analysis and PLSDA discriminant analysis. The results evidenced that the combined information from the three techniques gave good classification of the samples neatly distinguishing the APIs from European countries from the APIs manufactured out of Europe. In particular, NIR spectroscopy provided effective separation between European and non-European manufacturers and ¹H-NMR or LC-MS added specific information related to the separation. Concerning LC-MS Q-TOF, the analysis of multiple isobaric peaks proved to be highly predictive of the drug substance origin and emerged as a promising tool in the field of medicine traceability.

NMR spectroscopy and chemometric models to detect a specific non-porcine ruminant contaminant in pharmaceutical heparin

Heparin has been used successfully as a clinical antithrombotic for almost one century. Its isolation from animal sources (mostly porcine intestinal mucosa) involves multistep purification processes starting from the slaughterhouse (as mucosa) to the pharmaceutical plant (as the API). This complex supply chain increases the risk of contamination and adulteration, mainly with non-porcine ruminant material. The structural similarity of heparins from different origins, the natural variability of the heparin within samples from each source as well as the structural changes induced by manufacturing processes, require increasingly sophisticated methods capable of detecting low levels of contamination. The application of suitable multivariate classification approaches on API ¹H NMRspectra serve as rapid and reliable tools for product authentication and the detection of contaminants. Soft Independent Modeling of Class Analogies (SIMCA), Discriminant Analysis (DA), Partial Least Square Discriminant Analysis (PLS-DA) and local classification methods (kNN, BNN and N3) were tested on about one hundred certified heparin samples produced by 14 different manufacturers revealing that Partial Least Squares Discriminant Analysis (PLS-DA) provided the best discrimination of contaminated batches, with a balanced accuracy of 97%.

Differentiation among dairy products by combination of fast field cycling NMR relaxometry data and chemometrics

A set of commercial milk and Sicilian cheeses was analysed by a combination of fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry and chemometrics. The NMR dispersion (NMRD) curves were successfully analysed with a mathematical model applied on Parmigiano-Reggiano (PR) cheese. Regression parameters were led back to the molecular components of cheeses (water trapped in casein micelles, proteins and fats) and milk samples (water belonging to hydration shells around dispersed colloidal particles of different sizes and bulk water). The application of chemometric analysis on relaxometric data enabled differentiating milk from cheeses and revealing differences within the two sample groups of either cheeses or milk samples. Marked differences among cheeses were evidenced by statistical analysis of the sole quadrupolar peaks parameters, suggesting that these contain information on the nature of the milk used during cheese production. Hence, combination of FFC NMR and chemometrics represents a powerful tool to investigate alterations in dairy products.

2D NMR peak profiling to compare chemical differences between batches of pentosan polysulfate sodium

Pentosan Polysulfate Sodium (PPS) is a semi-synthetic polysulfated xylan sourced from beechwood tree barks. PPS, which is mainly composed of a xylose chain with branched O-methyl-glucuronate (MGA), can have heterogeneity in monosaccharide species, sequence and chemical modifications including sulfation and acetylation. The monosaccharide composition in polysaccharide therapeutics is a frequently quoted quality attribute (QA), which has been assessed using two-dimensional (2D) ¹H-¹³C HSQC NMR. However, the sensitivity of 2D NMR for the assessment of PPS inter-lot variability from the same manufacturer was unclear and questions remained whether 2D NMR had sufficient sensitivity to distinguish normal batch to batch variations in this QA. Here, a 2D peak profile method was applied to compare high-resolution semi-quantitative (semi-q) HSQC spectra with the inclusion of intermediate precision spectra collected on two PPS drug lots released 29 months apart (where one of the lots was expired). The semi-q HSQC NMR confirmed the mass equivalence of total polysaccharides, O-Methyl and acetyl groups between the two lots. The 2D spectral peak profile results readily identified significant lot-to-lot differences (p < 0.05) in relative distribution among most monosaccharide species, in addition to heterogeneity in MGA distribution and acetyl transfer from PPS to free acetate in the expired lot. Precisely measured chemical QAs are prerequisites to establish normal batch variation in the innovator product, providing important reference ranges for complex generic drug developers. Overall, high-resolution semi-q HSQC NMR may provide a sensitive tool to measure fine chemical differences in polysaccharide therapeutics needed to establish chemical QAs and compare batches without concerns of intrinsic NMR method variation.

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.

Minor N-Glycan Mapping of Monoclonal Antibody Therapeutics Using Middle-Down NMR Spectroscopy

The N-glycosylation pattern of Asn-297 may have impacts on monoclonal antibody (mAb) drug plasma clearance, antibody-dependent cell mediated cytotoxicity (ADCC), and complement-dependent cytotoxicity (CDC). Notably, the changes in the relative abundance of certain minor glycans, like the afucosylation, high-mannose, or galactosylation are known to change mAb properties and functions. Here, a middle-down NMR spectroscopy based analytical procedure was applied to assess the composition and structure of glycans on adalimumab and trastuzumab without glycan cleavage from the mAbs. The anomeric 2D ¹H-¹³C spectra showed distinct patterns that could be used to profile and differentiate mAb glycan compositions. Specifically, the anomeric C1/H1 resonances from N-acetylglucosamine (GlcNAc2 and -5) and mannose (Man4) were identified as characteristic peaks for key glycan anomeric linkages and branching states. They were also utilized for measuring the relative abundance of minor glycans of total afucosylation (aFuc%), high mannose (HM%), and branch specific galactosylation (Gal_1-3% and Gal_1-6%). The obtained total aFuc% value of 11-12% was similar between the two mAbs; however, trastuzumab had significantly lower level of high mannose and a higher level of galactosylation than adalimumab. Overall, the 2D-NMR measurements provided functionally relevant mAb glycan composition and structure information. The method was deemed fit-for-purpose for assessment of these mAb quality attributes and involved fewer chemical preparation steps than the classical approaches that cleave glycans prior to making measurements.

Quality Control of Heparin Injections: Comparison of Four Established Methods

Heparin is an anticoagulant medication that is usually injected subcutaneously. The quality of a set of commercial heparin injections from different producers was examined by NMR, IR, UV-Vis spectroscopies and potentiometric multisensor system. The type of raw material regarding heparin animal origin and producer, heparin molecular weight and activity values were derived based on the non-targeted analysis of 1H NMR fingerprints. DOSY NMR spectroscopy was additionally used to study homogeneity and additives profile. UV-Vis and IR, being cheaper than NMR, combined with multivariate statistics were successfully applied to study excipients composition as well as semi-estimation of activity values. Potentiometric multisensor measurements were found to be an important additional source of information about inorganic composition of finished heparin formulations. All investigated instrumental techniques are useful for finished heparin injections and should be selected according to availability as well as the information and confidence required for a specific sample.

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.

Tools for the Quality Control of Pharmaceutical Heparin

Heparin is a vital pharmaceutical anticoagulant drug and remains one of the few naturally sourced pharmaceutical agents used clinically. Heparin possesses a structural order with up to four levels of complexity. These levels are subject to change based on the animal or even tissue sources that they are extracted from, while higher levels are believed to be entirely dynamic and a product of their surrounding environments, including bound proteins and associated cations. In 2008, heparin sources were subject to a major contamination with a deadly compound-an over-sulphated chondroitin sulphate polysaccharide-that resulted in excess of 100 deaths within North America alone. In consideration of this, an arsenal of methods to screen for heparin contamination have been applied, based primarily on the detection of over-sulphated chondroitin sulphate. The targeted nature of these screening methods, for this specific contaminant, may leave contamination by other entities poorly protected against, but novel approaches, including library-based chemometric analysis in concert with a variety of spectroscopic methods, could be of great importance in combating future, potential threats.

Multivariate analysis applied to complex biological medicines

A biological medicine (or biologicals) is a term for a medicinal compound that is derived from a living organism. By their very nature, they are complex and often heterogeneous in structure, composition and biological activity. Some of the oldest pharmaceutical products are biologicals, for example insulin and heparin. The former is now produced recombinantly, with technology being at a point where this can be considered a defined chemical entity. This is not the case for the latter, however. Heparin is a heterogeneous polysaccharide that is extracted from the intestinal mucosa of animals, primarily porcine, although there is also a significant market for non-porcine heparin due to social and economical reasons. In 2008 heparin was adulterated with another sulfated polysaccharide. Unfortunately this event was disastrous and resulted in a global public health emergency. This was the impetuous to apply modern analytical techniques, principally NMR spectroscopy, and multivariate analyses to monitor heparin. Initially, traditional unsupervised multivariate analysis (principal component analysis (PCA)) was applied to the problem. This was able to distinguish animal heparins from each other, and could also separate adulterated heparin from what was considered bona fide heparin. Taught multivariate analysis functions by training the analysis to look for specific patterns within the dataset of interest. If this approach was to be applied to heparin, or any other biological medicine, it would have to be taught to find every possible alien signal. The opposite approach would be more efficient; defining the complex heterogeneous material by a library of bona fide spectra and then filtering test samples with these spectra to reveal alien features that are not consistent with the reference library. This is the basis of an approach termed spectral filtering, which has been applied to 1D and 2D-NMR spectra, and has been very successful in extracting the spectral features of adulterants in heparin, as well as being able to differentiate supposedly biosimilar products. In essence, the filtered spectrum is determined by subtracting the covariance matrix of the library spectra from the covariance matrix of the library spectra plus the test spectrum. These approaches are universal and could be applied to biological medicines such as vaccine polysaccharides and monoclonal antibodies.

By-Products of Heparin Production Provide a Diverse Source of Heparin-like and Heparan Sulfate Glycosaminoglycans

Global production of pharmaceutical heparin (Hp) is increasing, and the production process from raw mucosal material results in large amounts of waste by-products. These contain lower sulfated Hp-like and heparan sulfate (HS), as well as other glycosaminoglycans, which are bioactive entities with pharmaceutical potential. Here we describe the first purification, structural and functional characterisation of Hp-like and HS polysaccharides from the four major by-product fractions of standard heparin production. Analysis of the by-products by disaccharide composition analysis and NMR demonstrated a range of structural characteristics which differentiate them from Hp (particularly reduced sulfation and sulfated disaccharide content), and that they are each distinct. Functional properties of the purified by-products varied, each displaying distinct anticoagulant profiles in different assays, and all exhibiting significantly lower global and specific inhibition of the coagulation pathway than Hp. The by-products retained the ability to promote cell proliferation via fibroblast growth factor receptor signalling, with only minor differences between them. These collective analyses indicate that they represent an untapped and economical source of structurally-diverse Hp-like and HS polysaccharides with the potential for enhancing future structure-activity studies and uncovering new biomedical applications of these important natural products.

Oligosaccharide Chromatographic Techniques for Quantitation of Structural Process-Related Impurities in Heparin Resulting From 2-O Desulfation

Heparin is a widely-used intravenous anticoagulant comprising a complex mixture of highly-sulfated linear polysaccharides of repeating sequences of uronic acids (either iduronic or glucuronic) 1->4 linked to D-glucosamine with specific sulfation patterns. Preparation of crude heparin from mammalian mucosa involves protease digestion with alcalase under basic conditions (pH ≥ 9) and high temperature (>50°C) and also oxidation. Under such conditions, side reactions including the ubiquitous 2-O desulfation occur on the heparin backbone yielding non-endogenous disaccharides within polysaccharide chains. Whatever the process used for its manufacture, some level of corresponding degradation impurities is therefore expected to be found in heparin and the derived Low Molecular Weight Heparins. These impurities should be monitored to control the quality of the final therapeutic product. Two anion exchange chromatography techniques were used to analyze heparin samples exhaustively or partially depolymerized with heparinases and determine the proportions of non-endogenous disaccharides generated by side reactions during the manufacturing process (epoxides and galacturonic moieties). We also present data from a case study of marketed heparin. Current heparin sodium monographs do not directly address process impurities related to modification of the structure of heparin. Although desulfation reduces the overall biological potency, we found that heparin with an average of one modified disaccharide per chain can still comply with the USP or Ph. Eur. heparin sodium monographs requirements. We have implemented disaccharide analysis to monitor the quality of this product on a risk basis.

Fine structural characterization of sulodexide

Sulodexide is a heparinoid which combines the properties of its components heparin and dermatan sulfate and is used not only for the prophylaxis and treatment of thromboembolic diseases but also for the treatment of diabetic nephropathy. Despite many clinical studies have been conducted to investigate its activity and safety, no data are available on the fine chemical characterization of its components. In this work, the in-depth investigation on the structural features of both the whole mixture and the isolated components was accomplished, involving the analysis of molecular weight distribution and of their mono, di and oligosaccharide composition by HP-SEC/TDA, 2D-NMR and HPLC-MS techniques. Moreover, also the separation of fractions endowed of graded affinity to antithrombin was achieved followed again by detailed structural analysis. The combination of different techniques permits to profile in depth the structural features of such a drug and offers a useful tool for possible analysis of batch production.

Heparan Sulfate Proteoglycans as Relays of Neuroinflammation

Heparan sulfate proteoglycans (HSPGs) are implicated as inflammatory mediators in a variety of settings, including chemokine activation, which is required to recruit circulating leukocytes to infection sites. Heparan sulfate (HS) polysaccharide chains are highly interactive and serve co-receptor roles in multiple ligand:receptor interactions. HS may also serve as a storage depot, sequestering ligands such as cytokines and restricting their access to binding partners. Heparanase, through its ability to fragment HS chains, is a key regulator of HS function and has featured prominently in studies of HS's involvement in inflammatory processes. This review focuses on recent discoveries regarding the role of HSPGs, HS, and heparanase during inflammation, with particular focus on the brain. HS chains emerge as critical go-betweens in multiple aspects of the inflammatory response-relaying signals between receptors and cells. The molecular interactions proposed to occur between HSPGs and the pathogen receptor toll-like receptor 4 (TLR4) are discussed, and we summarize some of the contrasting roles that HS and heparanase have been assigned in diseases associated with chronic inflammatory states, including Alzheimer's disease (AD). We conclude by briefly discussing how current knowledge could potentially be applied to augment HS-mediated events during sustained neuroinflammation, which contributes to neurodegeneration in AD.