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.

Simultaneous quantitative determination of liraglutide and insulin degludec in rat plasma by liquid chromatography-tandem mass spectrometry method and its application.

A simple, fast and high-throughput LC-tandem mass spectrometry method was developed and validated to simultaneously measure liraglutide and insulin degludec in rat plasma. After protein precipitation, plasma samples were subjected to gradient elution using an InertSustain Bio C18 column with 1000/20/1 water/acetonitrile/formic acid (v/v/v) and 1000/1 acetonitrile/formic acid (v/v) as the mobile phase. The method was validated from 1.00 to 500 ng/mL of liraglutide and insulin degludec. Further, the extraction recovery from the plasma was 41.8%-49.2% for liraglutide and 56.5%-69.7% for insulin degludec. Intra- and inter-day precision of liraglutide was 3.5%-9.4% and 8.4%-9.8%, respectively, whereas its accuracy was between -12.6% and -1.3%. Intra- and inter-day precision of insulin degludec was 5.2%-13.6% and 11.8%-19.1%, respectively, showing an accuracy between -3.0% and 9.9%. As a result, the method was successfully applied to a pharmacokinetics study of liraglutide and insulin degludec following a single-dose subcutaneous administration to rats.

A sustained zero-order release carrier for long-acting, peakless basal insulin therapy.

Basal insulin therapy plays a key role in diabetes management. An ideal therapy should mimic the steady physiologic basal insulin secretion, and provide a peak-free, prolonged and steady insulin supply. Herein, a new drug carrier was designed by first PEGylating insulin and then incorporating the conjugate into layer-by-layer assembled films with tannic acid (TA). Because PEG-insulin and TA in the films were linked with reversible, dynamic hydrogen bonds, the films disintegrate gradually when soaked in aqueous solutions, and thus release PEG-insulin into the media. In vitro release tests revealed that the release of PEG-insulin follows a zero-order kinetics. Theoretical analysis based on the unique release mechanism also supports a zero-order kinetics. In vivo tests using a streptozotocin-induced diabetic rat model demonstrated that subcutaneous implantation of the film could maintain a steady plasma drug level and hence maintain a fasting blood glucose level (BGL) close to normal. The duration of action depends on the thickness of the film. Using a 50-bilayer film, fasting BGL was kept within the normoglycemic range for ∼16 days. Initial burst release, a severe problem for other release systems, was successfully avoided.

Expression, purification, and characterization of the Degludec precursor DesB30.

Diabetes is a chronic metabolic disease, for which recombinant human insulin is the most effective and mainstream treatment. DesB30 is an insulin analogue in which the B chain lacks amino acid 30 (Thr) compared with human insulin. This analogue can be used to produce the long-acting insulin Degludec or Detemir. In this study, a spacer peptide was added before the sequence of DesB30 and the C-peptide was replaced with AAK, a short connecting peptide. The target gene was cloned under the control of AOX1 and expressed as a secretory protein in Pichia pastoris. A high-yield recombination strain was selected by screening for resistance to G418. The basal salts medium was optimized and a lower salt concentration medium was found to show the best effects. Both media were used to compare the yield of high-density fermentation. The maximum yield reached 4.51 g/L in 1/2 basal salt medium, which is the highest reported yield to date. The insulin precursor, which is single-stranded, was purified by weak cation exchange chromatograph and preparative reversed-phase high-performance liquid chromatography (RP-HPLC), from which 73.39% of product was recovered at over 95% purity. The double-stranded protein (DesB30) was obtained by digesting the insulin precursor with trypsin. Using preparative RP-HPLC, the product was obtained with over 95% purity. Finally, the structure of DesB30 was confirmed.

Identification of recombinant human insulin and biosynthetic insulin analogues by multiplexed targeted unlabeled mass spectrometry of proteotypic tryptic peptides.

Direct qualitative methods that allow the rapid screening and identification of insulin products during early stages of the drug development process and those already in the market can be of great utility for manufacturers and regulatory agencies and the recent scientific literature describes several methods. Herein, a qualitative proteomic method is presented for the identification of recombinant human insulin and all marketed biosynthetic analogues -insulin lispro, aspart, glulisine, glargine, detemir and degludec- via tryptic digestion and identification of proteotypic peptides for each insulin. Individual insulins were first denatured under reducing conditions and the cysteine residues blocked by iodoacetamide. The proteins were then digested with trypsin and the peptide products separated by reversed phase liquid chromatography on an Ascentis® Express ES-C18 column and detected by positive polarity ESI-MS/MS. The digestion peptides were characterized using a multiplexed MRM approach that monitors the fragmentation of the doubly charged unlabeled precursor ion of each peptide into a collection of signature y and b ions. The MRM transitions for the individual peptides were optimized to allow maximal ionization on a standard triple quadrupole mass spectrometer. All products of the digestion procedure for all insulins were detected with adequate signal intensity except for the C-terminal B30Thr whenever it was present and cleaved and the tryptic B1-3 tripeptide of insulin glulisine. The unique proteotypic peptides identified for each of the insulin analogues coupled with their signature y and b ions permitted the unambiguous verification of all sequence variations and chemical modifications. The elution of the A polypeptide chain for all insulins and the tryptic peptides of the B chain, with the exception of a very few, occurred around the same time point. This underscores the close similarity in the physicochemical properties between the digestion peptides and is consistent with the subtle variations in amino acid sequence among the various insulins. Therefore, the identification and distinction of the different types of insulin based solely on the chromatographic retention time of their respective proteolytic products can be deceptive without proper mass spectrometric analysis and may result in false positives.

Solution structures of long-acting insulin analogues and their complexes with albumin.

The lipidation of peptide drugs is one strategy to obtain extended half-lives, enabling once-daily or even less frequent injections for patients. The half-life extension results from a combination of self-association and association with human serum albumin (albumin). The self-association and association with albumin of two insulin analogues, insulin detemir and insulin degludec, were investigated by small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) in phenolic buffers. Detemir shows concentration-dependent self-association, with an equilibrium between hexamer, dihexamer, trihexamer and larger species, while degludec appears as a dihexamer independent of concentration. The solution structure of the detemir trihexamer has a bent shape. The stoichiometry of the association with albumin was studied using DLS. For albumin-detemir the molar stoichiometry was determined to be 1:6 (albumin:detemir ratio) and for albumin-degludec it was between 1:6 and 1:12 (albumin:degludec ratio). Batch SAXS measurements of a 1:6 albumin:detemir concentration series revealed a concentration dependence of complex formation. The data allowed the modelling of a complex between albumin and a detemir hexamer and a complex consisting of two albumins binding to opposite ends of a detemir dihexamer. Measurements of size-exclusion chromatography coupled to SAXS revealed a complex between a degludec dihexamer and albumin. Based on the results, equilibria for the albumin-detemir and albumin-degludec mixtures are proposed.

Fabrication of long-acting insulin formulation based on poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles: preparation, optimization, characterization, and in vitro evaluation.

The purpose of this research was the fabrication, statistical optimization, and in vitro characterization of insulin-loaded poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanoparticles (INS-PHBV-NPs). Nanopar-ticles were successfully developed by double emulsification solvent evaporation method. The NPs were characterized for particle size, entrapment efficiency (EE%), and polydispersity index (PDI). The NPs also were characterized by scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and circular dichroism (CD). The optimum conditions were found to be 1.6% polyvinyl alcohol (PVA), 0.9% of PHBV, and 15 mg/ml of insulin with the aid of the Box-Behnken experimental design results. The optimized NPs showed spherical shape with particle size of 250.21 ± 11.37 nm, PDI of 0.12 ± 0.01, and with EE% of 90.12 ± 2.10%. In vitro drug release pattern followed Korsmeyer-Peppas model and exhibited an initial burst release of 19% with extended drug release of 63.2% from optimized NPs within 27 d. In conclusion, these results suggest that INS-PHBV-NPs could be a promising candidate for designing an injectable sustained release formulation for insulin.

Strategy for peptide quantification using LC-MS in regulated bioanalysis: case study with a glucose-responsive insulin.

AIM: Advances in technology have led to a shift for peptide quantification from traditional ligand-binding assays to LC-MS/MS-based analysis, which presents challenges, in other assay sensitivity, specificity and ruggedness, in addition to lacking of regulatory guidance, especially for the hybrid assay format. Methodology & results: This report communicates a strategy that has been employed in our laboratories for method development and assay validation, and exemplified in a case study of MK-2640, a glucose-responsive insulin, in multiple matrices. Intact MK-2640 was monitored, while immunoaffinity purification and SPE were used to support the rat/dog GLP and clinical studies, respectively. The rationale and considerations behind our approach, as well as the acceptance criteria applied to the assay validation are discussed.

Optimization of a Coupling Process for Insulin Degludec According to a Quality by Design (QbD) Paradigm.

This case study described a successful application of the quality by design (QbD) principles to a coupling process development of insulin degludec. Failure mode effects analysis (FMEA) risk analysis was first used to recognize critical process parameters (CPPs). Five CPPs, including coupling temperature (Temp), pH of desB30 solution (pH), reaction time (Time), desB30 concentration (Conc), and molar equivalent of ester per mole of desB30 insulin (MolE), were then investigated using a fractional factorial design. The curvature effect was found significant, indicating the requirement of second-order models. Afterwards, a central composite design was built with an augmented star and center points study. Regression models were developed for the CPPs to predict the purity and yield of predegludec using above experimental data. The R2 and adjusted R2 were higher than 96 and 93% for the two models respectively. The Q2 values were more than 80% indicating a good predictive ability of models. MolE was found to be the most significant factor affecting both yield and purity of predegludec. Temp, pH, and Conc were also significant for predegludec purity, while Time appeared to remarkably influence the yield model. The multi-dimensional design space and normal operating region (NOR) with a robust setpoint were determined using a probability-based Monte-Carlo simulation method. The verified experimental results showed that the design space was reliable and effective. This study enriches the understanding of acetylation process and is instructional to other complicated operations in biopharmaceutical engineering.

Glargine and degludec: Solution behaviour of higher dose synthetic insulins.

Single, double and triple doses of the synthetic insulins glargine and degludec currently used in patient therapy are characterised using macromolecular hydrodynamic techniques (dynamic light scattering and analytical ultracentrifugation) in an attempt to provide the basis for improved personalised insulin profiling in patients with diabetes. Using dynamic light scattering and sedimentation velocity in the analytical ultracentrifuge glargine was shown to be primarily dimeric under solvent conditions used in current formulations whereas degludec behaved as a dihexamer with evidence of further association of the hexamers ("multi-hexamerisation"). Further analysis by sedimentation equilibrium showed that degludec exhibited reversible interaction between mono- and-di-hexamer forms. Unlike glargine, degludec showed strong thermodynamic non-ideality, but this was suppressed by the addition of salt. With such large injectable doses of synthetic insulins remaining in the physiological system for extended periods of time, in some case 24-40 hours, double and triple dose insulins may impact adversely on personalised insulin profiling in patients with diabetes.

Using Dextran-encapsulated gold nanoparticles as insulin carriers to prolong insulin activity.

AIM: Diabetes mellitus is commonly treated with painful insulin injections. We aim to explore drug carriers that can prolong insulin activity. MATERIALS & METHODS: Dextran-encapsulated gold NPs (AuNPs@Dextran) that can bind with insulin are used as insulin carriers. The affinity (K d = ∼42 pM) between insulin and insulin receptors on the cells is much higher than that (K d = ∼4.02 µM) of insulin and AuNPs@Dextran. Thus, insulin released from the AuNP@Dextran-insulin conjugates to maintain kinetic equilibrium and prefers to bind to the insulin receptor. The slow release of insulin from the AuNP@Dextran-insulin conjugates facilitates the lasting of insulin activity. RESULTS & DISCUSSION: AuNP@Dextran-insulin conjugates can prolong insulin activity to 12 h, whereas free form insulin loses activity after 4 h in adipocyte cells. CONCLUSION: AuNPs@Dextran are suitable carriers that can prolong insulin activity.

Short- and Longterm Glycemic Control of Streptozotocin-Induced Diabetic Rats Using Different Insulin Preparations.

The chemical induction of diabetes with STZ has gained popularity because of the relative ease of rendering normal animals diabetic. Insulin substitution is required in STZ-rats in long-term studies to avoid ketoacidosis and consequently loss of animals. Aim of the present studies was to test different insulin preparations and different ways of administration in their ability to reduce blood glucose in STZ-induced diabetic rats. Single dosing of the long-acting insulin analogue glargine was able to dose-dependently reduce blood glucose over 4 h towards normoglycemia in STZ-treated rats. However, this effect was not sustained until 8 h post injection. A more sustained glucose-lowering effect was achieved using insulin-releasing implants. In STZ-rats, 1 insulin implant moderately lowered blood glucose levels 10 days after implantation, while 2 implants induced normoglycemia over the whole day. According to the glucose-lowering effect 1 as well as 2 insulin implants significantly reduced HbA1c measured after 26 days of implantation. In line with the improved glucose homeostasis due to the implants, urinary glucose excretion was also blunted in STZ-treated rats with 2 implants. Since diabetic nephropathy is one of the complications of longterm diabetes, renal function was characterized in the STZ-rat model. Increases in creatinine clearance and urinary albumin excretion resemble early signs of diabetic nephropathy. These functional abnormalities of the kidney could clearly be corrected with insulin-releasing implants 27 days after implantation. The data show that diabetic STZ-rats respond to exogenous insulin with regard to glucose levels as well as kidney parameters and a suitable dose of insulin implants for glucose control was established. This animal model together with the insulin dosing regimen is suitable to address diabetes-induced early diabetic nephropathy and also to study combination therapies with insulin for the treatment of type 1 diabetes.

Twice-daily insulin degludec/insulin aspart provides superior fasting plasma glucose control and a reduced rate of hypoglycaemia compared with biphasic insulin aspart 30 in insulin-naïve adults with Type 2 diabetes.

AIM: To evaluate the efficacy and safety of twice-daily insulin degludec/insulin aspart vs. twice-daily biphasic insulin aspart 30 in people with Type 2 diabetes mellitus who were naïve to insulin. METHODS: In this 26-week, multinational, open-label, controlled, two-arm, parallel-group, treat-to-target trial, participants [mean (± sd) age 58.9 (±8.9) years, duration of diabetes 9.5 (±5.9) years, HbA1c 68 (±8.7) mmol/mol or 8.4 (±0.8)% and BMI 31.2 (±4.2) kg/m(2) ) were randomized (1:1) to insulin degludec/insulin aspart (n = 197) or biphasic insulin aspart 30 (n = 197), administered with breakfast and the main evening meal, titrated to a self-monitored plasma glucose target > 3.9 and ≤ 5.0 mmol/l. RESULTS: The mean HbA1c was reduced to 49 mmol/mol (6.6%) with insulin degludec/insulin aspart and 48 mmol/mol (6.5%) with biphasic insulin aspart 30. Insulin degludec/insulin aspart achieved the prespecified non-inferiority margin (estimated treatment difference 0.02%; 95% CI -0.12, 0.17). Insulin degludec/insulin aspart was superior in lowering fasting plasma glucose (estimated treatment difference -1.00 mmol/l; 95% CI -1.4, -0.6; P < 0.001) and reducing overall and nocturnal confirmed hypoglycaemia at a similar overall insulin dose compared with biphasic insulin aspart 30. Similar proportions of participants in each arm experienced severe hypoglycaemia. Adverse events were equally distributed. CONCLUSIONS: Consistent with previous findings, insulin degludec/insulin aspart twice daily effectively improved long-term glycaemic control, with superior reductions in FPG, and significantly less overall and nocturnal confirmed hypoglycaemia compared with biphasic insulin aspart 30 in people with Type 2 diabetes who were insulin-naïve.

[Future of ultra long-acting insulin analogues].

Optimal insulin therapy should mimic endogenous insulin secretion in healthy subjects and maintain normal glycemic control. Short- or rapid-acting insulin is used to mimic the response of insulin secretion after meal. Basal insulin restrains hepatic glucose production in fasting state, and should be mimicked by neutral protamine Hagedorn (NPH) or long-acting insulin. Long-acting basal insulin analogues offer some advantage over the NPH insulin in terms of less glycemic variability when used once daily. Various scientific associations recommend once-daily basal insulin when starting insulin therapy; therefore, long-acting basal insulin analogues play important part of continual and optimal insulin therapy. In this article, we review long-acting basal insulin analogues currently available in Japan and new basal insulin in research and development phase.

Review of Clinical Profile of IDegAsp.

In patients with diabetes, treatment intensification requires basal and bolus insulin injections to control the fasting and prandial insulin needs. To overcome the burden of multiple daily injections, co-formulating basal and bolus insulins in single injection could allow a simple regimen with fewer injections. Current premixed insulin analogues are limited by the protaminated insulin component, which cannot provide effective basal coverage. While, long-acting insulin analogues like insulin glargine and insulin detemir cannot be combined with rapid-acting insulin analogues due to physicochemical incompatibility. Insulin degludec/insulin aspart (IDegAsp) is a soluble co-formulation of two distinct insulin analogues in the ratio of 70% ultra-long-acting insulin degludec (IDeg) and 30% rapid-acting insulin aspart (IAsp). The distinct PK/PD properties of IDeg and IAsp components are preserved in the co-formulation, with the rapid absorption characteristics of IAsp and flat and stable profile of IDeg maintained separately. Size exclusion chromatography studies of IDegAsp indicate that IDeg and lAsp exist as stable di-hexamers and hexamers, respectively in the formulation. Moreover, at steady state, the prandial and basal glucose lowering effects of IDeg and IAsp were distinct and clearly separated. A clear dose-response relationship was observed in patients with type 1 and type 2 diabetes treated with IDegAsp. The glucose lowering effects of basal and prandial components of IDegAsp are maintained in elderly (≥ 65 years of age) patients with type 1 diabetes. In addition, the PK and clearance of IDeg and IAsp are not affected by mild, moderate or severe renal or hepatic impairment. Presence of two distinct insulin analogues, as a soluble co-formulation with basal component with an ultra-long duration of action makes IDegAsp an advance to premix insulins.

Concentrated insulin glargine (Toujeo) for diabetes.

Toujeo, the new 300 IU/mL formulation of insulin glargine, is as effective as insulin glargine 100 IU/mL (Lantus) in lowering HbA1c, and might cause less hypoglycemia.

Investigation of the Physico-Chemical Properties that Enable Co-Formulation of Basal Insulin Degludec with Fast-Acting Insulin Aspart.

PURPOSE: To study the self-association states of insulin degludec and insulin aspart alone and combined in pharmaceutical formulation and under conditions simulating the subcutaneous depot. METHODS: Formulations were made of 0.6 mM degludec at 3 and 5 Zn/6 insulin monomers, and 0.6 mM aspart (2 Zn/6 insulin monomers). Self-association was assessed using size-exclusion chromatography (SEC) monitored by UV and orthogonal reverse-phase chromatography. RESULTS: Simulating pharmaceutical formulation, degludec eluted as dihexamers, whereas aspart eluted as hexamers and monomers. Combining degludec at low zinc with aspart increased dihexamer content, indicating hybrid hexamer formation. At high zinc concentration, however, there was no evidence of this. Simulating the subcutaneous depot by removing preservative, degludec eluted as multihexamers and aspart as monomers. Aspart was incorporated into the multihexamer structures when combined with degludec at low zinc, but there was no such interaction with high-zinc degludec. SEC using progressively diluted concentrations of phenol and m-cresol showed that dissociation of aspart into monomers occurs before the formation of degludec multihexamers. CONCLUSION: Insulins degludec and aspart can be combined without forming hybrid hexamers, but this combinability is dependent on zinc and preservative concentration, and requires that degludec is fully dihexameric before addition of aspart.

Direct comparison of radioimmunoassay and LC-MS/MS for PK assessment of insulin glargine in clinical development.

BACKGROUND: A direct comparison of radioimmunoassay (RIA) and LC-MS/MS for insulin glargine quantification in human plasma is provided. RESULTS: Compared with the RIA, the LC-MS/MS assay exhibited comparable/improved sensitivity (LLOQ at 0.1 ng/ml [˜16.7 pM or 2.8 µU/ml] for glargine and its metabolites M1 and M2, respectively) and ruggedness. Most importantly, it demonstrated a superior specificity advantage against the interference from endogenous insulin, exogenous insulin analogs (e.g., Novolog(®), Humalog(®) or Levemir(®), routine treatment for diabetes mellitus) and potentially pre-existing anti-insulin antibodies in patient samples. The data obtained from diabetic patients suggested the LC-MS/MS assay substantially improved pharmacokinetic characterization of glargine. CONCLUSION: LC-MS/MS overcame common limitations of RIA, and provided critically needed specificity to support glargine clinical development, without sacrificing assay sensitivity and ruggedness.

Ideal basal insulin: opportunities from designer proteins.

Ideally, the insulin therapy must aim at the creation of a near normal glycaemic profile without the barriers of unacceptable weight gain or hypoglycaemia. Provision of a flexible insulin regimen would further enhance adherence to the prescribed therapy and positively impact glycaemic control. Insulin degludec addresses many of the aspirations of ideal basal insulin. Long duration of action, flat pharmacodynamic profile, low day-to-day variability translate into benefits of predictable glucose excursions, lower risk of hypoglycaemia at same glycaemic level and effective glycaemic with one daily injection in individuals. In conclusion, insulin degludec represents an important advancement in the treatment of type 1 and 2 diabetes.

Translating structure to clinical properties of an ideal basal insulin.

There is a need for ideal basal insulin which can overcome the unmet need of a truly once daily insulin, with a flat peakless profile. Useful for all types of patients Insulin degludec is next generation insulin with a unique mode of protraction of forming soluble multi-hexamers and slow continuous absorption giving it a flat profile compared to the existing basal insulin. In patients with type 1 diabetes or with type 2 diabetes, at steady-state, the mean terminal half-life of insulin degludec was 25 hours, i.e., approximately twice as long as for insulin glargine (half-life of 12.1 hours). In once-daily dosing regimen it reaches steady state after approximately 3 days. The duration of action of insulin degludec was estimated to be beyond 42 hours in euglycaemic clamp studies and this gives the unique opportunity of flexible time dosing which is not an available option with the existing basal insulin. The glucose-lowering effect is evenly distributed across a 24-hour dosing interval with insulin degludec having 4 times lower variability than insulin glargine. This is an important attribute given the narrow therapeutic window of insulin and the goal of achieving night time and inter-prandial glycaemic control without increasing the risk for hypoglycaemia, a goal that is challenging given the variability of absorption and lower PK half-lives of current basal insulin products. The combination of the ultra-long, flat and stable profile with an improved hour-to-hour and day-to-day variability could present an improved risk-benefit trade-off with the lower risk of hypoglycaemia, allowing for targeting improved levels of glycaemic control.