Water Proton NMR for In Situ Detection of Insulin Aggregates

Anionic lipid catalyzes the generation of cytotoxic insulin oligomers

Misfolding and aggregation of proteins into amyloidogenic assemblies are key features of several metabolic and neurodegenerative diseases. Human insulin has long been known to form amyloid fibrils under various conditions, which affects its bioavailability and function. Clinically, insulin aggregation at recurrent injection sites poses a challenge for diabetic patients who rely on insulin therapy. Furthermore, decreased responsiveness to insulin in type 2 diabetic (T2D) patients may lead to its overproduction and accumulation as aggregates. Earlier reports have reported that various factors such as pH, temperature, agitation, and the presence of lipids or other proteins influence insulin aggregation. Our present study aims to elucidate the effects of non-micellar anionic DMPG (1,2-dimyristoyl-sn-glycero-3-phosphoglycerol) lipids on insulin aggregation. Distinct pathways of insulin aggregation and intermediate formation were observed in the presence of DMPG using a ThT fluorescence assay. The formation of soluble intermediates, alongside large insulin fibrils, was observed in insulin incubated with DMPG via TEM, DLS and NMR, as opposed to insulin aggregates generated without lipids. 13C magic angle spinning solid-state NMR and FTIR experiments indicated that lipids do not alter the conformation of insulin fibrils but do alter the time scale of motion of aromatic and aliphatic sidechains. Furthermore, the soluble intermediates were found to be more cytotoxic as compared to fibrils generated with or without lipids. Overall, our study elucidates the importance of anionic lipids in dictating the pathways and intermediates associated with insulin aggregation. These findings could be useful in determining various approaches to avoid toxicity and enhance the effectiveness of insulin in therapeutic applications.

Low-field NMR Works as a Rapid, Automatic, Non-Invasive and Wide-Scale Coverage Technique for Aggregates Indication in Biomacromolecule Development

Protein aggregation is challenging for biopharmaceutical drug, because it affects the stability of protein formulations in real-time. However, current techniques for protein aggregate indication meet a number of limitations including limited aggregate size range, complex pre-treatments and lack of chromatographic approaches. Herein, a rapid, automatic, non-invasive and wide-scale coverage technique for aggregates indication is developed to overcome these challenges. Firstly, the response of low-field nuclear magnetic resonance (LF-NMR) to the aggregates is explored by making a comparison with certain established techniques. LF-NMR achieves a high sensitivity of water proton transverse relaxation rate (R2 of H2O, hereinafter referred as R2(H2O)) to protein aggregates from nanometer to micrometer. Then, the quantitative relationship between R2(H2O) and aggregates is investigated furtherly. R2(H2O) could serve as an all-size coverage protein aggregates indicator during development. As a non-invasive method, LF-NMR does not need any sample handling. It takes only 44 s for one test, and saves a lot of manpower, materials and costs. Compared with other established analytical techniques, the technique developed here could be a powerful tool for a rapid, automatic, non-invasive and wide-scale coverage technique for aggregates indication in biomacromolecule development.

Decoupling Protein Concentration and Aggregate Content Using Diffusion and Water NMR

Protein-based biopharmaceutical drugs, such as monoclonal antibodies, account for the majority of the best-selling drugs globally in recent years. For bioprocesses, key performance indicators are the concentration and aggregate level for the product being produced. In water NMR (wNMR), the use of the water transverse relaxation rate [R2(1H2O)] has been previously used to determine protein concentration and aggregate level; however, it cannot be used to separate between them without using an additional technique. This work shows that it is possible to "decouple" these two key characteristics by recording the water diffusion coefficient [D(1H2O)] in conjunction with R2(1H2O), even in the event of overlap in either D(1H2O) or R2(1H2O). This method is demonstrated on three different systems, following appropriate D(1H2O) or R2(1H2O) calibration data acquisition for a protein of interest. Our method highlights the potential use of benchtop NMR as an at-line process analytical technique.

TGA and NMR relaxation measurement of nonmesoporous silica to investigate the amount of hydrolysis product in acetylsalicylic acid adsorbed on silica

This study investigated a crucial surface property of silica that contributes to the chemical stability of acetylsalicylic acid (ASA) physically adsorbed on silica. Hydrophilic nonmesoporous types of silica were selected, and the number of hydroxyl groups on silica (N(OH)) was evaluated using thermogravimetric analysis (TGA). The ASA-containing silica was stored at 40 °C in drying conditions, and the amount of ASA degradation was quantified based on salicylic acid. From the scatterplots between the number of hydroxyl groups per unit weight (specific surface area (SSA) × N(OH)) and the amount of ASA degradation, it was clarified that in ASA adsorbed on silica, the ASA chemical stability was determined by the formula (the SSA × N(OH)). In addition, a time-domain nuclear magnetic resonance measurement verified the N(OH) result by estimating the interaction between the silica surface and water in an aqueous silica suspension. The N(OH) result was found to be reasonable.

In-situ biophysical characterization of high-concentration protein formulations using wNMR

High-concentration protein formulation is of paramount importance in patient-centric drug product development, but it also presents challenges due to the potential for enhanced aggregation and increased viscosity. The analysis of critical quality attributes often necessitates the transfer of samples from their primary containers together with sample dilution. Therefore, there is a demand for noninvasive, in situ biophysical methods to assess protein drug products directly in primary sterile containers, such as prefilled syringes, without dilution. In this study, we introduce a novel application of water proton nuclear magnetic resonance (wNMR) to evaluate the aggregation propensity of a high-concentration drug product, Dupixent® (dupilumab), under stress conditions. wNMR results demonstrate a concentration-dependent, reversible association of dupilumab in the commercial formulation, as well as irreversible aggregation when exposed to accelerated thermal stress, but gradually reversible aggregation when exposed to freeze and thaw cycles. Importantly, these results show a strong correlation with data obtained from established biophysical analytical tools widely used in the pharmaceutical industry. The application of wNMR represents a promising approach for in situ noninvasive analysis of high-concentration protein formulations directly in their primary containers, providing valuable insights for drug development and quality assessment.

Usefulness of Applying Partial Least Squares Regression to T2 Relaxation Curves for Predicting the Solid form Content in Binary Physical Mixtures

This study applied partial least squares (PLS) regression to nuclear magnetic resonance (NMR) relaxation curves to quantify the free base of an active pharmaceutical ingredient powder. We measured the T₂ relaxation of intact and moisture-absorbed physical mixtures of tetracaine free base (TC) and its hydrochloride salt (TC·HCl). The obtained T₂ relaxation curves were analyzed by two methods, one using a previously reported T₂ relaxation time (T₂), and the other using PLS regression. The accuracy of estimating TC was inadequate when using previous T₂ values because the moisture-absorbed physical mixtures showed biphasic T₂ relaxation curves. By contrast, the entire measured whole of the T₂ relaxation curves was used as input variables and analyzed by PLS regression to quantify the content of TC in the moisture-absorbed TC/TC·HCl. Based on scatterplots of theoretical versus predicted TC, the obtained PLS model exhibited acceptable coefficients of determination and relatively low root mean squared error values for calibration and validation data. The statistical values confirmed that an accurate and reliable PLS model was created to quantify TC in even moisture-absorbed TC/TC·HCl. The bench-top low-field NMR instrument used to apply PLS regression to the T₂ relaxation curve may be a promising tool in process analytical technology.

Correlated analytical and functional evaluation of higher order structure perturbations from oxidation of NISTmAb

The clinical efficacy and safety of protein-based drugs such as monoclonal antibodies (mAbs) rely on the integrity of the protein higher order structure (HOS) during product development, manufacturing, storage, and patient administration. As mAb-based drugs are becoming more prevalent in the treatment of many illnesses, the need to establish metrics for quality attributes of mAb therapeutics through high-resolution techniques is also becoming evident. To this end, here we used a forced degradation method, time-dependent oxidation by hydrogen peroxide, on the model biotherapeutic NISTmAb and evaluated the effects on HOS with orthogonal analytical methods and a functional assay. To monitor the oxidation process, the experimental workflow involved incubation of NISTmAb with hydrogen peroxide in a benchtop nuclear magnetic resonance spectrometer (NMR) that followed the reaction kinetics, in real-time through the water proton transverse relaxation rate R₂(¹H₂O). Aliquots taken at defined time points were further analyzed by high-field 2D ¹H-¹³C methyl correlation fingerprint spectra in parallel with other analytical techniques, including thermal unfolding, size-exclusion chromatography, and surface plasmon resonance, to assess changes in stability, heterogeneity, and binding affinities. The complementary measurement outputs from the different techniques demonstrate the utility of combining NMR with other analytical tools to monitor oxidation kinetics and extract the resulting structural changes in mAbs that are functionally relevant, allowing rigorous assessment of HOS attributes relevant to the efficacy and safety of mAb-based drug products.

Inspecting Insulin Products Using Water Proton NMR. I. Noninvasive vs Invasive Inspection

BACKGROUND

There is a clear need to transition from batch-level to vial/syringe/pen-level quality control of biologic drugs, such as insulin. This could be achieved only by noninvasive and quantitative inspection technologies that maintain the integrity of the drug product.

METHODS

Four insulin products for patient self-injection presented as prefilled pens have been noninvasively and quantitatively inspected using the water proton NMR technology. The inspection output is the water proton relaxation rate R₂(¹H₂O), a continuous numerical variable rather than binary pass/fail.

RESULTS

Ten pens of each product were inspected. R₂(¹H₂O) displays insignificant variation among the 10 pens of each product, suggesting good insulin content uniformity in the inspected pens. It is also shown that transferring the insulin solution out of and then back into the insulin pen caused significant change in R₂(¹H₂O), presumably due to exposure to O₂ in air.

CONCLUSIONS

Water proton NMR can noninvasively and quantitatively inspect insulin pens. wNMR can confirm product content uniformity, but not absolute content. Its sensitivity to sample transferring provides a way to detect drug product tampering. This opens the possibility of inspecting every pen/vial/syringe by manufacturers and end-users.

Quality Assurance of Commercial Insulin Formulations: Novel Assay Using Infrared Spectroscopy

BACKGROUND

For insulins in commercial formulations, degradation can be observed within the certified shelf life when not stored at recommended conditions. Elevated temperatures and exposure to shear forces can cause changes in the secondary structure of the hormone, leading to a decrease in pharmaceutical potency. International pharmacopoeia recommendations for insulin quality monitoring assays mainly rely on liquid chromatography methods. These methods are unable to distinguish between active and inactive forms, both of which may exist in pharmaceutical insulins exposed to stress conditions.

METHOD

Infrared attenuated total reflection spectroscopy has been used for the analysis of insulin dry film preparations using affordable instrumentation. This method can be applied to either formulated insulin specimens or pure insulins obtained by ultrafiltration. Such samples have been stored under different temperatures (0°C, 20°C, and 37°C), and degradation processes have been monitored up to a period of a few months.

RESULTS

By analyzing specific shifts of absorption bands in the infrared spectra, which are sensitive to the protein secondary structure, even small structural changes in the hormone become evident. Another option is amide I band deconvolution into individual bands, which can be attributed to secondary structure subunits that are part of the insulin tertiary structure.

CONCLUSION

A novel and innovative method based on infrared attenuated total reflection spectroscopy of insulin dry films is a promising analytical tool for quantifying the degree of insulin degradation, as it provides information on indicating a decrease in biological potency. The established methods for insulin potency assays require animal testing or clamp experiments on people with diabetes.

Systematic stability testing of insulins as representative biopharmaceuticals using ATR FTIR-spectroscopy with focus on quality assurance

SIGNIFICANCE

Bioactive proteins represent the most important component class in biopharmaceutical products for therapeutic applications. Their production is most often biotechnologically realized by genetically engineered microorganisms. For the quality assurance of insulins as representatives of life-saving pharmaceuticals, analytical methods are required that allow more than total protein quantification in vials or batches. Chemical and physical factors such as unstable temperatures or shear rate exposure under storage can lead to misfolding, nucleation, and subsequent fibril forming of the insulins. The assumption is valid that these processes go parallel with a decrease in bioactivity.

AIM

Infrared (IR) spectroscopy has been successfully utilized for secondary structure analysis in cases of protein misfolding and fibril formation.

APPROACH

A reliable method for the quantification of the secondary structure changes has been developed using insulin dry-film Fourier-transform IR spectroscopy in combination with the attenuated total reflection (ATR) technique and subsequent data analyses such as band-shift determination, spectral band deconvolution, and principal component analysis.

RESULTS

A systematic study of insulin spectra was carried out on model insulin specimens, available either as original formulations or as hormones purified by ultrafiltration. Insulin specimens were stored at different temperatures, i.e., 0°C, 20°C, and 37°C, respectively, for up to three months. Weekly ATR-measurements allowed the monitoring of hormone secondary structure changes, which are supposed to be negatively correlated with insulin bioactivity.

CONCLUSIONS

It could be shown that IR-ATR spectroscopy offers a fast and reliable analytical method for the determination of secondary structural changes within insulin molecules, as available in pharmaceutical insulin formulations and therefore challenges internationally established measurement techniques for quality control regarding time, costs, and effort of analysis.

Comprehensive Assessment of Protein and Excipient Stability in Biopharmaceutical Formulations Using 1H NMR Spectroscopy

Biopharmaceutical proteins are important drug therapies in the treatment of a range of diseases. Proteins, such as antibodies (Abs) and peptides, are prone to chemical and physical degradation, particularly at the high concentrations currently sought for subcutaneous injections, and so formulation conditions, including buffers and excipients, must be optimized to minimize such instabilities. Therefore, both the protein and small molecule content of biopharmaceutical formulations and their stability are critical to a treatment's success. However, assessing all aspects of protein and small molecule stability currently requires a large number of analytical techniques, most of which involve sample dilution or other manipulations which may themselves distort sample behavior. Here, we demonstrate the application of 1H nuclear magnetic resonance (NMR) spectroscopy to study both protein and small molecule content and stability in situ in high-concentration (100 mg/mL) Ab formulations. We show that protein degradation (aggregation or fragmentation) can be detected as changes in 1D 1H NMR signal intensity, while apparent relaxation rates are specifically sensitive to Ab fragmentation. Simultaneously, relaxation-filtered spectra reveal the presence and degradation of small molecule components such as excipients, as well as changes in general solution properties, such as pH. 1H NMR spectroscopy can thus provide a holistic overview of biopharmaceutical formulation content and stability, providing a preliminary characterization of degradation and acting as a triaging step to guide further analytical techniques.

FT-IR versus EC-QCL spectroscopy for biopharmaceutical quality assessment with focus on insulin-total protein assay and secondary structure analysis using attenuated total reflection

For the quality control of biopharmaceutical products, which contain proteins as the most important active ingredients, shelf life may be limited due to inappropriate storage conditions or mechanical stress. For insulins as representatives of life-saving pharmaceuticals, analytical methods are needed, which are providing additional information than obtained by assays for total protein quantification. Despite sophisticated formulations, the chemical stability may be challenged by temperatures deviating from recommended conditions or shear rate exposure under storage, leading to misfolding, nucleation, and subsequent fibril formation, accompanied by a decrease in bioactivity. A reliable method for insulin quantification and determination of secondary structure changes has been developed by attenuated total reflection (ATR) Fourier-transform infrared spectroscopy of insulin formulations by a silver halide fiber-coupled diamond probe with subsequent dry-film preparation. A special emphasis has been placed on the protein amide I band evaluation, for which spectral band analysis provides unique information on secondary structure fractions for intact and misfolded insulins. Quantitative measurements are possible down to concentrations of less than 0.5 mg/ml, whereas the dry-film preparation delivers high signal-to-noise ratios due to the prior water evaporation, thus allowing a reliable determination of secondary structure information. Graphical abstract.

The Hydration Shell of Monomeric and Dimeric Insulin Studied by Terahertz Time-Domain Spectroscopy

Protein aggregation is believed to be a significant biological mechanism related to neurodegenerative disease, which makes the early-stage detection of aggregates a major concern. We demonstrated the use of terahertz (THz) time-domain spectroscopy to study protein-water interaction of monomeric and dimeric bovine insulin in aqueous samples. Regulated by changing pH and verified by size-exclusion chromatography and dynamic light scattering, we then measured their concentration-dependent changes in THz absorption between 0.5 and 3.0 THz and quantitatively deduced the extended hydration shell thickness by cubic distribution model and random distribution model. Under a random distribution assumption, the extended hydration thickness is 15.4 ± 0.4 Å for monomeric insulin and 17.5 ± 0.5 Å for dimeric insulin, with the hydration number of 6700 and 11,000, respectively. The hydration number of dimeric insulin is not twice but 1.64 times that of monomeric insulin, further supported by the ratio of solvent-accessible surface area. This "1.64-times" relation probably originates from the structural and conformational changes accompanied with dimerization. Combined with the investigations on insulin samples with different single amino acid mutations, residue B24 is believed to play an important role in the dimerization process. It is demonstrated that THz time-domain spectroscopy is a useful tool and has the sensitivity to provide the hydration information of different protein aggregates at an early stage.

A nondestructive and noninvasive method to determine water content in lyophilized proteins using low-field time-domain NMR

Determining the moisture content in lyophilized solids is a fundamental step towards predicting the quality and stability of lyophilized products, but conventional methods are time-consuming, invasive, and destructive. High levels of residual moisture in a lyophilized product can lead to cake collapse, product degradation, and reduced shelf life. The aim of this study was to develop a fast, noninvasive, nondestructive, and inexpensive method for determining the moisture content in a lyophilized monoclonal antibody (mAb) formulation using benchtop low-field time-domain nuclear magnetic resonance spectroscopy.

Separation, Characterization and Discriminant Analysis of Subvisible Particles in Biologics Formulations

Background:

The presence of subvisible particles (SVPs) in parenteral formulations of biologics is a major challenge in the development of therapeutic protein formulations. Distinction between proteinaceous and non-proteinaceous SVPs is vital in monitoring formulation stability.

Methods:

The current compendial method based on light obscuration (LO) has limitations in the analysis of translucent/low refractive index particles. A number of attempts have been made to develop an unambiguous method to characterize SVPs, albeit with limited success.

Results:

Herein, we describe a robust method that characterizes and distinguishes both potentially proteinaceous and non-proteinaceous SVPs in protein formulations using Microflow imaging (MFI) in conjunction with the MVAS software (MFI View Analysis Suite), developed by ProteinSimple. The method utilizes two Intensity parameters and a morphological filter that successfully distinguishes proteinaceous SVPs from non-proteinaceous SVPs and mixed aggregates.

Conclusion:

he MFI generated raw data of a protein sample is processed through Lumetics LINK software that applies an in-house developed filter to separate proteinaceous from the rest of the particulates.

An Evaluation of the Potential of NMR Spectroscopy and Computational Modelling Methods to Inform Biopharmaceutical Formulations

Protein-based therapeutics are considered to be one of the most important classes of pharmaceuticals on the market. The growing need to prolong stability of high protein concentrations in liquid form has proven to be challenging. Therefore, significant effort is being made to design formulations which can enable the storage of these highly concentrated protein therapies for up to 2 years. Currently, the excipient selection approach involves empirical high-throughput screening, but does not reveal details on aggregation mechanisms or the molecular-level effects of the formulations under storage conditions. Computational modelling approaches have the potential to elucidate such mechanisms, and rapidly screen in silico prior to experimental testing. Nuclear Magnetic Resonance (NMR) spectroscopy can also provide complementary insights into excipient–protein interactions. This review will highlight the underpinning principles of molecular modelling and NMR spectroscopy. It will also discuss the advancements in the applications of computational and NMR approaches in investigating excipient–protein interactions.

Water proton NMR detection of amide hydrolysis and diglycine dimerization

The transverse relaxation rate of water protons R2(1H2O) is found to be sensitive to amide hydrolysis and diglycine dimerization. The results demonstrate the feasibility of using R2(1H2O) as a diagnostic tool to detect chemical changes in aqueous solutions. Potential applications include drug product formulation and inspection.