Molecular variants and derivatives of insulin for improved glycemic control in diabetes

Improving the stability of insulin through effective chemical modifications: A Comprehensive review

Insulin, an essential peptide hormone, conjointly regulates blood glucose levels by its receptor and it is used as vital drug to treat diabetes. This therapeutic hormone may undergo different chemical modifications during industrial processes, pharmaceutical formulation, and through its endogenous storage in the pancreatic β-cells. Insulin is highly sensitive to environmental stresses and readily undergoes structural changes, being also able to unfold and aggregate in physiological conditions. Even; small changes altering the structural integrity of insulin may have significant impacts on its biological efficacy to its physiological and pharmacological activities. Insulin analogs have been engineered to achieve modified properties, such as improved stability, solubility, and pharmacokinetics, while preserving the molecular pharmacology of insulin. The casually or purposively strategies of chemical modifications of insulin occurred to improve its therapeutic and pharmaceutical properties. Knowing the effects of chemical modification, formation of aggregates, and nanoparticles on protein can be a new look at the production of protein analogues drugs and its application in living system. The project focused on effects of chemical modifications and nanoparticles on the structure, stability, aggregation and their results in effective drug delivery system, biological activity, and pharmacological properties of insulin. The future challenge in biotechnology and pharmacokinetic arises from the complexity of biopharmaceuticals, which are often molecular structures that require formulation and delivery strategies to ensure their efficacy and safety.

Discrete, Chiral Polymer-Insulin Conjugates

Polymer conjugation has been widely used to improve the stability and pharmacokinetics of therapeutic biomacromolecules; however, conventional methods to generate such conjugates often use disperse and/or achiral polymers with limited functionality. The heterogeneity of such conjugates may lead to manufacturing variability, poorly controlled biological performance, and limited ability to optimize structure-property relationships. Here, using insulin as a model therapeutic polypeptide, we introduce a strategy for the synthesis of polymer-protein conjugates based on discrete, chiral polymers synthesized through iterative exponential growth (IEG). These conjugates eliminate manufacturing variables originating from polymer dispersity and poorly controlled absolute configuration. Moreover, they offer tunable molecular features, such as conformational rigidity, that can be modulated to impact protein function, enabling faster or longer-lasting blood glucose responses in diabetic mice when compared to PEGylated insulin and the commercial insulin variant Lantus. Furthermore, IEG-insulin conjugates showed no signs of decreased activity, immunogenicity, or toxicity following repeat dosing. This work represents a significant step toward the synthesis of precise synthetic polymer-biopolymer conjugates and reveals that fine tuning of synthetic polymer structure may be used to optimize such conjugates in the future.

Application of machine learning methods for the prediction of true fasting status in patients performing blood tests

The fasting blood glucose (FBG) values extracted from electronic medical records (EMR) are assumed valid in existing research, which may cause diagnostic bias due to misclassification of fasting status. We proposed a machine learning (ML) algorithm to predict the fasting status of blood samples. This cross-sectional study was conducted using the EMR of a medical center from 2003 to 2018 and a total of 2,196,833 ontological FBGs from the outpatient service were enrolled. The theoretical true fasting status are identified by comparing the values of ontological FBG with average glucose levels derived from concomitant tested HbA1c based on multi-criteria. In addition to multiple logistic regression, we extracted 67 features to predict the fasting status by eXtreme Gradient Boosting (XGBoost). The discrimination and calibration of the prediction models were also assessed. Real-world performance was gauged by the prevalence of ineffective glucose measurement (IGM). Of the 784,340 ontologically labeled fasting samples, 77.1% were considered theoretical FBGs. The median (IQR) glucose and HbA1c level of ontological and theoretical fasting samples in patients without diabetes mellitus (DM) were 94.0 (87.0, 102.0) mg/dL and 5.6 (5.4, 5.9)%, and 92.0 (86.0, 99.0) mg/dL and 5.6 (5.4, 5.9)%, respectively. The XGBoost showed comparable calibration and AUROC of 0.887 than that of 0.868 in multiple logistic regression in the parsimonious approach and identified important predictors of glucose level, home-to-hospital distance, age, and concomitantly serum creatinine and lipid testing. The prevalence of IGM dropped from 27.8% based on ontological FBGs to 0.48% by using algorithm-verified FBGs. The proposed ML algorithm or multiple logistic regression model aids in verification of the fasting status.

Oligomerization of Pharmaceutically Relevant Insulin Analogues for Varying Concentration and Salinity Revealed by Small-Angle X-ray Scattering

Two different insulin analogues, insulin degludec and lithocholyl insulin, were studied by small-angle X-ray scattering with respect to their self-assembly and interactions in solution at different concentrations of insulin and salt, NaCl. Very different behavior was observed for the two. Insulin degludec, linked to a hexadecanedioic acid, consistently formed di-hexamers, without any further oligomeric growth upon screening of electrostatic repulsions, indicating a stable di-hexamer unit without further oligomerization, as expected in the presence of phenol. The other insulin analogue, linked to the sterol lithocholic acid, formed n-hexamers with n ranging from 1 to 15, increasing with NaCl concentration and insulin concentration, indicating attractive forces in competition with the electrostatic repulsion and solution entropy. At the highest concentration of insulin and NaCl, a liquid crystal phase was observed, which has not previously been identified, featuring a quadratic structure organized into layers, which might hold interesting properties for pharmaceutical applications.

Applications of X-ray Powder Diffraction in Protein Crystallography and Drug Screening

Providing fundamental information on intra/intermolecular interactions and physicochemical properties, the three-dimensional structural characterization of biological macromolecules is of extreme importance towards understanding their mechanism of action. Among other methods, X-ray powder diffraction (XRPD) has proved its applicability and efficiency in numerous studies of different materials. Owing to recent methodological advances, this method is now considered a respectable tool for identifying macromolecular phase transitions, quantitative analysis, and determining structural modifications of samples ranging from small organics to full-length proteins. An overview of the XRPD applications and recent improvements related to the study of challenging macromolecules and peptides toward structure-based drug design is discussed. This review congregates recent studies in the field of drug formulation and delivery processes, as well as in polymorph identification and the effect of ligands and environmental conditions upon crystal characteristics. These studies further manifest the efficiency of protein XRPD for quick and accurate preliminary structural characterization.

An NMR-Based Similarity Metric for Higher Order Structure Quality Assessment Among U.S. Marketed Insulin Therapeutics

Protein or peptide higher order structure (HOS) is a quality attribute that could affect therapeutic efficacy and safety. Where appropriate, the HOS similarity between a proposed follow-on product and the reference listed drug should be demonstrated during regulatory assessment. Establishing quantitative HOS similarity for 2 drug substances, manufactured by different processes, has been challenging. Herein, HOS differences among U.S. marketed insulin drug products (DPs) were quantified using nuclear magnetic resonance spectra and principal component analysis (PCA). Then, the unitless Mahalanobis distance (D_M) in PCA space was calculated between insulin analog reference listed drugs and their recently approved follow-on products, and all D_M values were 3.29 or less. By contrast, a larger D_M value of 20.5 was obtained between the 2 insulin human DPs independently approved. However, upon mass-balanced and reversible dialysis of the 2 insulin human DPs against the same buffers, the D_M value was reduced to 1.19 or less. Thus, the observed range of nuclear magnetic resonance-PCA-derived D_M values can be used as a robust and sensitive measure of HOS similarity. Overall, the D_M values of 3.3 for DP and 1.2 for drug substances using insulin therapeutics represented realistic and achievable similarity metrics for developing generic or biosimilar drugs, quality assurance, or control.

Identification of N-Terminally Truncated Derivatives of Insulin Analogs Formed in Pharmaceutical Formulations

PURPOSE

Isolation and identification of unknown impurities of recombinant insulin lispro (produced at IBA) formed during accelerated stability testing of pharmaceutical solutions. For comparative purposes also commercially available formulations of recombinant human insulin (Humulin S®; Lilly), recombinant insulin lispro (Humalog®; Lilly), recombinant insulin aspart (NovoRapid® Penfill®; Novo Nordisk), recombinant insulin detemir (Levemir®; Novo Nordisk) and recombinant insulin glargine (Lantus®; Sanofi-Aventis) were analyzed.

METHODS

The impurities of insulin analogs were isolated by RP-HPLC and identified with peptide mass fingerprinting using MALDI-TOF/TOF mass spectrometry.

RESULTS

The identified derivatives were N-terminally truncated insulin analog impurities of decreased molecular mass of 119, 147 and 377 Da related to the original protein. The modifications resulting in a mass decrease were detected at the N-terminus of B chains of insulin lispro, insulin aspart, human insulin, insulin glargine, insulin detemir in all tested formulations. To our knowledge it is the first time that these impurities are reported.

CONCLUSIONS

The following derivatives formed by truncation of the B chain in insulin analogs were identified in pharmaceutical formulations: desPheB1-N-formyl-ValB2 derivative, desPheB1 derivative, pyroGluB4 derivative.

Human insulin polymorphism upon ligand binding and pH variation: the case of 4-ethylresorcinol

This study focuses on the effects of the organic ligand 4-ethylresorcinol on the crystal structure of human insulin using powder X-ray crystallography. For this purpose, systematic crystallization experiments have been conducted in the presence of the organic ligand and zinc ions within the pH range 4.50-8.20, while observing crystallization behaviour around the isoelectric point of insulin. High-throughput crystal screening was performed using a laboratory X-ray diffraction system. The most representative samples were selected for synchrotron X-ray diffraction measurements, which took place at the European Synchrotron Radiation Facility (ESRF) and the Swiss Light Source (SLS). Four different crystalline polymorphs have been identified. Among these, two new phases with monoclinic symmetry have been found, which are targets for the future development of microcrystalline insulin drugs.

Functions and roles of proteins: diabetes as a paradigm

Molecular and cellular biology has moved towards complete and accurate knowledge of how molecules behave in space and time. Protein is considered as the primary group of molecules responsible for mediating most physiological processes. Changes in the levels of proteins may lead to the altered function and are responsible for many diseases. This review provides a partial molecular explanation of biological force-ratio generation that may act to split protein into branches, and shows molecular functional divergence. Developing a non-reductionist theory of the cellular function in medicine is clearly not sufficient. Finding effective parameters of the models by characterizing molecular interactions becomes necessary. Protein interactivity and stability provides a basis for an integrated understanding of pathologies such diabetes. One example of how a mechanistic analysis of such physiological processes can be of value is the time-delay between mRNA and translation that can act as a fork allowing a slowdown in gene expression.

Polymeric hydrogels for oral insulin delivery

The search for an effective and reliable oral insulin delivery system has been a major challenge facing pharmaceutical scientists for over many decades. Even though innumerable carrier systems that protect insulin from degradation in the GIT with improved membrane permeability and biological activity have been developed, yet a clinically acceptable device is not available for human application. Efforts in this direction are continuing at an accelerated speed. One of the preferred systems widely explored is based on polymeric hydrogels that protect insulin from enzymatic degradation in acidic stomach and delivers effectively in the intestine. Swelling and deswelling mechanisms of the hydrogel under varying pH conditions of the body control the release of insulin. The micro and nanoparticle (NP) hydrogel devices based on biopolymers have been widely explored, but their applications in human insulin therapy are still far from satisfactory. The present review highlights the recent findings on hydrogel-based devices for oral delivery of insulin. Literature data are critically assessed and results from different laboratories are compared.

Metal ion controlled self-assembly of a chemically reengineered protein drug studied by small-angle X-ray scattering

Precise control of the oligomeric state of proteins is of central importance for biological function and for the properties of biopharmaceutical drugs. Here, the self-assembly of 2,2'-bipyridine conjugated monomeric insulin analogues, induced through coordination to divalent metal ions, was studied. This protein drug system was designed to form non-native homo-oligomers through selective coordination of two divalent metal ions, Fe(II) and Zn(II), respectively. The insulin type chosen for this study is a variant designed for a reduced tendency toward native dimer formation at physiological concentrations. A small-angle X-ray scattering analysis of the bipyridine-modified insulin system confirmed an organization into a novel well-ordered structure based on insulin trimers, as induced by the addition of Fe(II). In contrast, unmodified monomeric insulin formed larger and more randomly structured assemblies upon addition of Fe(II). The addition of Zn(II), on the other hand, led to the formation of small quantities of insulin hexamers for both the bipyridine-modified and the unmodified monomeric insulin. Interestingly, the location of the bipyridine-modification significantly affects the tendency to hexamer formation as compared to the unmodified insulin. Our study shows how combining a structural study and chemical design can be used to obtain molecular understanding and control of the self-assembly of a protein drug. This knowledge may eventually be employed to develop an optimized in vivo drug release profile.

Comparative pharmacodynamic and pharmacokinetic characteristics of subcutaneous insulin glulisine and insulin aspart prior to a standard meal in obese subjects with type 2 diabetes

AIMS

A multinational, randomized, double-blind, two-way crossover trial to compare the pharmacokinetic and pharmacodynamic properties of bolus, subcutaneously administered insulin glulisine (glulisine) and insulin aspart (aspart) in insulin-naÏve, obese subjects with type 2 diabetes.

METHODS

Thirty subjects [9/21 females/males; mean ± SD age: 60.7 ± 7.7 years; body mass index (BMI): 33.5 ± 3.3 kg/m(2) ; duration of diabetes: 6.8 ± 4.6 years; HbA1c: 7.1 ± 0.8%] were included in the analysis. They fasted overnight and then received a 0.2 U/kg subcutaneous dose of glulisine or aspart 2 min before starting a standardized test meal, 7 days apart, according to a randomization schedule. Blood samples were taken every 15 min, starting 20 min before the meal and ending 6 h postprandially.

RESULTS

The area under the absolute glucose concentration-time curve between 0 and 1 h after insulin injection and maximal glucose concentration was significantly lower with glulisine than with aspart (p = 0.0455 and 0.0337, respectively). However, for the total study period, plasma glucose concentration was similar for glulisine and aspart. Peak insulin concentration was significantly higher for glulisine than for insulin aspart (p < 0.0001). Hypoglycaemic events (≤ 70 mg/dl with or without symptoms) occurred in 13 and 16 subjects treated with glulisine and aspart, respectively, but there were no cases of severe hypoglycaemia requiring intervention.

CONCLUSIONS

Glulisine was associated with lower glucose levels during the first hour after a standard meal; the remaining glucose profiles were otherwise equivalent, with higher insulin levels observed throughout the study period.

A comparison of preprandial insulin glulisine versus insulin lispro in people with Type 2 diabetes over a 12-h period

A comparison of the plasma glucose and insulin day profiles between two prandial rapid-acting insulin analogues, insulin glulisine (glulisine) and insulin lispro (lispro), in 18 obese subjects with Type 2 diabetes. Subjects (body mass index: males, 36.7 [33.2-43.8] kg/m(2); females, 40.0 [35.7-46.5] kg/m(2)) received subcutaneous glulisine or lispro (0.15 U/kg) at 4-h intervals immediately (within 2 min) before three standard test meals during each of two 12-h, randomised, open-label, crossover studies (7+/-2-day interval between each). Overall, preprandial-subtracted glucose concentrations (area under the curve) were similar on the glulisine and lispro study days. However, the mean of the three maximal preprandial subtracted plasma glucose concentrations (DeltaGLU(max)) were lower with glulisine versus lispro (12%; p<0.01). Mean concentrations of insulin analogue were significantly higher post-meal with glulisine (p<0.01 for all). Post hoc analysis showed a significantly faster absorption rate for glulisine versus lispro in the first 30 min post-meal (estimated difference 0.48 microU/min; p<0.0001). Only two cases of hypoglycaemia were reported; both from one subject during the lispro day. When glulisine is injected immediately before a meal in obese patients with Type 2 diabetes, glulisine achieves significantly lower glucose excursions over lispro. Significantly faster absorption with higher and sustained post-meal levels of insulin analogue was achieved at every meal with glulisine versus lispro.