NMR Spectroscopy for Protein Higher Order Structure Similarity Assessment in Formulated Drug Products

Higher Order Structure Differences Among Insulin Crystalline Drugs Revealed by 2D heteronuclear NMR

During therapeutic protein development, two-dimensional (2D) heteronuclear NMR spectra can be a powerful analytical method for measuring protein higher order structure (HOS) in solution since the spectra exhibit much higher resolution than homonuclear 1H spectra. However, 2D NMR capabilities for characterizing protein HOS in crystalline states remain to be assessed, given the low 13C natural abundance and intrinsically broader lines in solid-state NMR (SSNMR). Herein, high-resolution heteronuclear correlation (HETCOR) SSNMR was utilized to directly measure intact crystal drug products of insulin human, insulin analogs of insulin lispro and insulin aspart. The fingerprint regions in 2D 1H-13C HETCOR spectra were identified, which distinguished the insulin crystals in their primary structure, HOS heterogeneity and dynamics, as well as the manufacturing processes. The HOS heterogeneity in insulin analogs is consistent with their therapeutic effect of rapid action; while insulin human crystals showed more structural homogeneity, consistent with their slower pharmacokinetics (PK) peak time than insulin analogs. Therefore, heteronuclear NMR could be broadly applicable to study protein drug dosage forms from liquid to solid, yielding improved molecular level structure data for assessing drug HOS in biosimilar drug development.

Analytical sameness methodology for the evaluation of structural, physicochemical, and biological characteristics of Armlupeg: A pegfilgrastim biosimilar case study

Pegfilgrastim is administered as an adjunct to chemotherapy to reduce the incidence of febrile neutropenia and associated infectious complications. Lupin's Pegfilgrastim is a proposed biosimilar to the U.S.-referenced Neulasta®. Demonstration of biosimilarity requires extensive physicochemical and functional characterization of the biosimilar, and demonstration of analytical similarity to the reference product, in addition to clinical studies. This work is a case study for demonstrating the analytical similarity of Armlupeg (Lupin's Pegfilgrastim) to Neulasta® with respect to structural and physicochemical attributes using several robust, orthogonal, and state-of-the-art techniques including high-end liquid chromatography, mass spectrometry, and spectroscopy techniques; circular dichroism; differential scanning calorimetry; nuclear magnetic resonance; analytical ultracentrifugation; and micro-flow imaging. Functional similarity was demonstrated using an in vitro cell proliferation assay to measure relative potency and surface plasmon resonance to measure receptor binding kinetics. Furthermore, comparative forced-degradation studies were performed to study the degradation of the products under stress conditions. The product attributes were ranked based on a critical quality attributes risk score according to their potential clinical impact. Based on criticality, all analyses were statistically evaluated to conclude analytical similarity. Lupin's Pegfilgrastim was comparable to Neulasta® as demonstrated via structural, functional, and purity analyses. Lupin's Pegfilgrastim complied with the quality and statistical ranges established using Neulasta®. Both products follow the same degradation pathways under stress conditions as observed in the forced-degradation studies. No new impurity or degradation product was observed in Lupin's Pegfilgrastim. These data conclusively demonstrate the analytical similarity of Lupin's Pegfilgrastim and Neulasta®.

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.

Mahalanobis distance correlation: A novel approach for quantitating changes in multidimensional NMR spectra in biological applications

We present here a novel protocol for quantitating changes in the NMR spectra, which is based on Mahalanobis statistics. In a two dimensional NMR spectrum, the various peaks are taken to represent a distribution, and the two chemical shifts along the orthogonal axes and the peak intensities constitute three observables. All these observables vary in a correlated manner. Taking account of these, the Mahalanobis distance (MD) reflects the distance of any chosen peak from the centre of the distribution. For quantitating changes in a particular spectrum (say A) with N peaks (altered protein NMR spectrum) with respect to a reference spectrum (say B) with M peaks (original protein NMR spectrum), a composite spectrum with N + M peaks is generated. A one-to-one correspondence between N MD values considering all the N peaks in A and the same N peaks in the composite spectrum (A + B) is calculated. The MD distance of corresponding peaks in two different distributions can be correlated to assess the changes in the spectra during the course of a biological phenomenon, or as a result of biomolecular interactions. We have demonstrated these ideas, first, using the ¹H-¹⁵N HSQC spectrum of Ubiquitin, and then application of these has been demonstrated for monitoring progression of fibrillation of the protein α-Synuclein, in absence and presence of safranal, a known inhibitor of fibrillation of the protein. The method is in general applicable to multidimensional NMR spectra, does not require extensive data collection, and allows quantitative assessment of spectral changes via a single parameter. We believe that the method will have wide ranging applications to monitor many biological phenomena, and will also be useful in an industrial environment for mass comparison of molecules in a rapid manner.

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.