Absorption kinetics and action profiles of subcutaneously administered insulin analogues (AspB9GluB27, AspB10, AspB28) in healthy subjects

Characterization and impact of peptide physicochemical properties on oral and subcutaneous delivery

Peptides, an emerging modality within the biopharmaceutical industry, are often delivered subcutaneously with evolving prospects on oral delivery. Barrier biology within the subcutis or gastrointestinal tract is a significant challenge in limiting absorption or otherwise disrupting peptide disposition. Aspects of peptide pharmacokinetic performance and ADME can be mitigated with careful molecular design that tailors for properties such as effective size, hydrophobicity, net charge, proteolytic stability, and albumin binding. In this review, we endeavor to highlight effective techniques in qualifying physicochemical properties of peptides and discuss advancements of in vitro models of subcutaneous and oral delivery. Additionally, we will delineate empirical findings around the relationship of these physicochemical properties and in vivo (animal or human) impact. We conclude that robust peptide characterization methods and in vitro techniques with demonstrated correlations to in vivo data are key routines to incorporate in the drug discovery and development to improve the probability of technical and commercial success of peptide therapeutics.

Review: Pharmacology of insulin

Diabetes is associated with microvascular and macrovascular complications leading to significant morbidity and mortality. Glycaemic control is important to prevent and delay the progression of these complications. An ideal insulin regimen in patients with diabetes would mirror the 24-hour insulin profile of a non-diabetic person and thereby prevent hyperglycaemia without inducing hypoglycaemia. This has, until recently, proved difficult to reproduce by regular subcutaneous insulin injections due to the inherent pharmacokinetic properties of the available insulins. Normoglycaemia was rarely achieved without hypoglycaemia compromising the quality of patients' lives. The advent of the new long- and short-acting insulin analogues are expected to both improve glycaemic control leading to a reduction in diabetes-related complications and reduce the incidence of hypoglycaemia thereby offering patients a better lifestyle.

Obesity and Diabetes: The Increased Risk of Cancer and Cancer-Related Mortality

Obesity and type 2 diabetes are becoming increasingly prevalent worldwide, and both are associated with an increased incidence and mortality from many cancers. The metabolic abnormalities associated with type 2 diabetes develop many years before the onset of diabetes and, therefore, may be contributing to cancer risk before individuals are aware that they are at risk. Multiple factors potentially contribute to the progression of cancer in obesity and type 2 diabetes, including hyperinsulinemia and insulin-like growth factor I, hyperglycemia, dyslipidemia, adipokines and cytokines, and the gut microbiome. These metabolic changes may contribute directly or indirectly to cancer progression. Intentional weight loss may protect against cancer development, and therapies for diabetes may prove to be effective adjuvant agents in reducing cancer progression. In this review we discuss the current epidemiology, basic science, and clinical data that link obesity, diabetes, and cancer and how treating obesity and type 2 diabetes could also reduce cancer risk and improve outcomes.

Pharmacokinetic Model of the Transport of Fast-Acting Insulin From the Subcutaneous and Intradermal Spaces to Blood

Pharmacokinetic (PK) models describing the transport of insulin from the injection site to blood assist clinical decision making and are part of in silico platforms for developing and testing of insulin delivery strategies for treatment of patients with diabetes. The ability of these models to accurately describe all facets of the in vivo insulin transport is therefore critical for their application. Here, we propose a new model of fast-acting insulin analogs transport from the subcutaneous and intradermal spaces to blood that can accommodate clinically observed biphasic appearance and delayed clearance of injected insulin, 2 phenomena that are not captured by existing PK models. To develop the model we compare 9 insulin transport PK models which describe hypothetical insulin delivery pathways potentially capable of approximating biphasic appearance of exogenous insulin. The models are tested with respect to their ability to describe clinical data from 10 healthy volunteers which received 1 subcutaneous and 2 intradermal insulin injections on 3 different occasions. The optimal model, selected based on information and posterior identifiability criteria, assumes that insulin is delivered at the administrative site and is then transported to the bloodstream via 2 independent routes (1) diffusion-like process to the blood and (2) combination of diffusion-like processes followed by an additional compartment before entering the blood. This optimal model accounts for biphasic appearance and delayed clearance of exogenous insulin. It agrees better with the clinical data as compared to commonly used models and is expected to improve the in silico development and testing of insulin treatment strategies, including artificial pancreas systems.

Absorption Mechanism of a Physical Complex of Monomeric Insulin and Deoxycholyl-l-lysyl-methylester in the Small Intestine

Currently, oral administration of insulin still remains the best option to avoid the burden of repeated subcutaneous injections and to improve its pharmacokinetics. The objective of the present investigation was to demonstrate the absorption mechanism of insulin in the physical complexation of deoxycholyl-l-lysyl-methylester (DCK) for oral delivery. The oral insulin/DCK complex was prepared by making a physical complex of insulin aspart with DCK through ion-pair interaction in water. For the cellular uptake study, fluorescein-labeled insulin or DCK were prepared according to a standard protocol and applied to Caco-2 or MDCK cell lines. For the PK/PD studies, we performed intrajejunal administration of different formulation of insulin/DCK complex to diabetic rats. The resulting insulin and DCK complex demonstrated greatly enhanced lipophilicity as well as increased permeation across Caco-2 monolayers. The immunofluorescence study revealed the distribution of the complex in the cytoplasm of Caco-2 cells. Moreover, in the apical sodium bile acid transporter (ASBT) transfected MDCK, the insulin/DCK complex showed interaction with ASBT, and also demonstrated absorption through passive diffusion. We could not find that any evidence of endocytosis in relation to the uptake of insulin complex in vitro. In the rat intestine model, the highest absorption of insulin complex was observed in the jejunum at 1 h and then in the ileum at 2-4 h. In PK/PD study, the complex showed a similar PK profile to that of SC insulin. Overall, the study showed that the effect of DCK on enhancing the absorption of insulin resulted from transcellular processes as well as bile acid transporter activity.

Can glucose be monitored accurately at the site of subcutaneous insulin delivery?

Because insulin promotes glucose uptake into adipocytes, it has been assumed that during measurement of glucose at the site of insulin delivery, the local glucose level would be much lower than systemic glucose. However, recent investigations challenge this notion. What explanations could account for a reduced local effect of insulin in the subcutaneous space? One explanation is that, in humans, the effect of insulin on adipocytes appears to be small. Another is that insulin monomers and dimers (from hexamer disassociation) might be absorbed into the circulation before they can increase glucose uptake locally. In addition, negative cooperativity of insulin action (a lower than expected effect of very high insulin concentrations)may play a contributing role. Other factors to be considered include dilution of interstitial fluid by the insulin vehicle and the possibility that some of the local decline in glucose might be due to the systemic effect of insulin. With regard to future research, redundant sensing units might be able to quantify the effects of proximity, leading to a compensatory algorithm. In summary, when measured at the site of insulin delivery, the decline in subcutaneous glucose level appears to be minimal, though the literature base is not large. Findings thus far support (1) the development of integrated devices that monitor glucose and deliver insulin and (2) the use of such devices to investigate the relationship between subcutaneous delivery of insulin and its local effects on glucose. A reduction in the number of percutaneous devices needed to manage diabetes would be welcome.

Bioavailability and variability of biphasic insulin mixtures

Absorption of subcutaneously administered insulin is associated with considerable variability. Some of this variability was quantitatively explained for both soluble insulin and insulin suspensions in a recent contribution to this journal (Søeborg et al., 2009). In the present article, the absorption kinetics for mixtures of insulins is described. This requires that the bioavailability of the different insulins is considered. A short review of insulin bioavailability and a description of the subcutaneous depot thus precede the presentation of possible mechanisms associated with subcutaneous insulin degradation. Soluble insulins are assumed to be degraded enzymatically in the subcutaneous tissue. Suspended insulin crystals form condensed heaps that are assumed to be degraded from their surface by invading macrophages. It is demonstrated how the shape of the heaps affects the absorption kinetics. Variations in heap formation thus explain some of the additional variability associated with suspended insulins (e.g. NPH insulins) compared to soluble insulins. The heap model also describes how increasing concentrations of suspended insulins lead to decreasing bioavailability and lower values of Cmax. Together, the findings constitute a comprehensive, quantitative description of insulin absorption after subcutaneous administration. The model considers different concentrations and doses of soluble insulin, including rapid acting insulin analogues, insulin suspensions and biphasic insulin mixtures. The results can be used in both the development of novel insulin products and in the planning of the treatment of insulin dependent diabetic patients.

Explorative study of pharmacokinetics and pharmacodynamics after change in basal insulin infusion rate

BACKGROUND

The use of insulin pumps is rapidly increasing and new, technologically more advanced pumps are continuously being developed. It is of interest to assess the clinical relevance of the many technical features of these pumps, e.g., the effect on pharmacokinetics and pharmacodynamics with change in infusion rate.

METHOD

The aim of this study was to explore the sequence of pharmacokinetic and pharmacodynamic changes after dose doubling of the basal insulin infusion rate with subcutaneous bolus insulin injections once an hour, continuous subcutaneous insulin infusion, and continuous intravenous insulin infusion. Ten type 1 diabetes mellitus patients were included. The insulin doses were calculated based on the habitual insulin doses. The study was designed as an open-labeled, single-center, randomized, crossover exploratory trial.

RESULTS

Dose doubling of the basal insulin infusion rate with the three different administration protocols did not result in any clinically relevant differences in the time courses of the pharmacokinetic and pharmacodynamic parameters. With all three administration protocols, we observed a time interval of more than 6 hours before a new steady state of insulin was achieved.

CONCLUSIONS

Our results indicate that frequent changes in basal subcutaneous insulin infusion rates are not of significant clinical relevance on a 24-hour basis. Regarding technological features of subcutaneous insulin pumps, no discernable advantages of increasing pump stroke frequency were found. This indicates that pump stroke frequency sophistication might not be of clinical relevance in pumps used for basal subcutaneous insulin infusion.

MATHEMATICAL MODELS OF SUBCUTANEOUS INJECTION OF INSULIN ANALOGUES: A MINI-REVIEW

In the last three decades, several models relevant to the subcutaneous injection of insulin analogues have appeared in the literature. Most of them model the absorption of insulin analogues in the injection depot and then compute the plasma insulin concentration. The most recent systemic models directly simulate the plasma insulin dynamics. These models have been and/or can be applied to the technology of the insulin pump or to the coming closed-loop systems, also known as the artificial pancreas. In this paper, we selectively review these models in detail and at point out that these models provide key building blocks for some important endeavors into physiological questions of insulin secretion and action. For example, it is not clear at this time whether or not picomolar doses of insulin are found near the islets and there is no experimental method to assess this in vivo. This is of interest because picomolar concentrations of insulin have been found to be effective at blocking beta-cell death and increasing beta-cell growth in recent cell culture experiments.

Insulin aspart: rapid control for postmeal glucose excursions

Insulin aspart is a rapid-acting insulin analog that can be used to control prandial glucose levels as part of basal-bolus therapy, in continuous subcutaneous insulin infusion or in combination with oral antidiabetic drugs. Compared with exogenous human soluble insulin, insulin aspart has a faster onset of action, a higher peak concentration and a shorter duration of action, and is therefore more comparable to the physiological prandial insulin response. Randomized clinical trials have shown efficacy and safety advantages with insulin aspart over human soluble insulin, in particular, improved postprandial glucose control and lower rates of hypoglycemia. Currently, insulin aspart has been approved for use not only in adults and children with diabetes mellitus, but also for pregnant women with diabetes, including those with gestational diabetes.

Within-patient variation of the pharmacokinetics of subcutaneously injected biphasic insulin aspart as assessed by compartmental modelling

AIMS/HYPOTHESIS

Pharmacokinetics of s.c. administered insulin preparations have been widely studied, mostly using descriptive measures such as AUC, time to peak, or the peak plasma concentration. Several compartmental modelling studies of single-bolus s.c. insulin pharmacokinetics have also appeared, with contrasting results regarding the feasibility of insulin pharmacokinetics modelling and the appropriate level of detail for such models. In this paper, we used compartmental models to study the pharmacokinetics of biphasic insulin aspart administered by multiple s.c. injections. The main objective was to assess the magnitude of the inter-and intra-subject variation in the kinetics.

MATERIALS AND METHODS

Analyses were performed on 24-h serum insulin concentrations measured in 20 type 1 diabetes subjects given three daily s.c. injections of biphasic insulin aspart.

RESULTS

Preliminary analysis of the AUC:dose ratio showed that the apparent kinetics are not constant throughout the three daily injections of the compound. A simple and robust compartmental model was shown to be appropriate for interpreting the observations, provided that one of its parameters (the first-order rate constant for transfer from the s.c. depot to plasma) is allowed to vary between injections.

CONCLUSIONS/INTERPRETATION

Population estimates of the chosen model show that intra-subject variations between injections is of the same order of magnitude as inter-subject variation, partially explaining the difficulties encountered when individually tailoring intensified insulin therapy. We conclude that the explicit consideration of a rather simple kinetic model will allow better experimental designs in the future study of s.c. insulin preparations.

Insulin kinetics in type-I diabetes: continuous and bolus delivery of rapid acting insulin

We investigated insulin lispro kinetics with bolus and continuous subcutaneous insulin infusion (CSII) modes of insulin delivery. Seven subjects with type-1 diabetes treated by CSII with insulin lispro have been studied during prandial and postprandial conditions over 12 hours. Eleven alternative models of insulin kinetics have been proposed implementing a number of putative characteristics. We assessed 1) the effect of insulin delivery mode, i.e., bolus or basal, on the insulin absorption rate, the effects of 2) insulin association state and 3) insulin dose on the rate of insulin absorption, 4) the remote insulin effect on its volume of distribution, 5) the effect of insulin dose on insulin disappearance, 6) the presence of insulin degradation at the injection site, and finally 7) the existence of two pathways, fast and slow, of insulin absorption. An iterative two-stage parameter estimation technique was used. Models were validated through assessing physiological feasibility of parameter estimates, posterior identifiability, and distribution of residuals. Based on the principle of parsimony, best model to fit our data combined the slow and fast absorption channels and included local insulin degradation. The model estimated that 67(53-82)% [mean (interquartile range)] of delivered insulin passed through the slow absorption channel [absorption rate 0.011(0.004-0.029) min(-1)] with the remaining 33% passed through the fast channel [absorption rate 0.021(0.011-0.040) min(-1)]. Local degradation rate was described as a saturable process with Michaelis-Menten characteristics [VMAX = 1.93(0.62 - 6.03) mU min(-1), KM = 62.6(62.6 - 62.6) mU]. Models representing the dependence of insulin absorption rate on insulin disappearance and the remote insulin effect on its volume of distribution could not be validated suggesting that these effects are not present or cannot be detected during physiological conditions.

Postprandial versus preprandial dosing of biphasic insulin aspart in elderly type 2 diabetes patients

Preprandial dosing (within 5 min before meal) and postprandial dosing (15-20 min after meal onset) of NovoLog Mix 70/30 (BIAsp 30, a biphasic formulation of insulin aspart, 30% soluble and 70% protamine-crystallized) were compared in elderly (> or =65 years) type 2 diabetes patients in this open-label, 12-week, crossover study. Ninety-three patients were treated with b.i.d. preprandial injections of BIAsp 30 during a 2-week run-in period and subsequently randomized to a 4-week treatment with either pre- or postprandial b.i.d. BIAsp 30, followed by crossover to the other regimen for 4 weeks. Mean plasma glucose values during a 4-h mealtest at the end of each treatment were similar for pre- and postprandial BIAsp 30 (153 +/- 58 mg/dl and 161 +/- 59 mg/dl, respectively, difference not significant). However, the mean blood glucose increment from self-measured blood glucose values was slightly but significantly greater after postprandial injection than after preprandial injection (treatment difference: 16.3mg/dl; 95% CI: [0.5, 29.3]). Fifty-six percent of patients reported a hypoglycemic episode; postprandial injection did not increase the incidence of hypoglycemia as compared to preprandial injection (113 episodes versus 125 episodes, respectively). For some elderly type 2 diabetes patients, postprandial injection of BIAsp 30 may be an acceptable alternative to standard preprandial injection.

Pharmacokinetic and pharmacodynamic properties of insulin aspart and human insulin

The preferred approach to determine the pharmacokinetic (PK) and pharmacodynamic (PD) properties of insulin analogues is the euglycemic glucose clamp. Currently non-compartmental data analytical approaches are used to analyze data. The purpose of the present study is to propose a novel compartmental-model for analysis of data from glucose clamp studies. Data used in this trial only involved 18 of the 20 originally treated subjects. Data was obtained from a crossover trial where 18 healthy subjects each received a single subcutaneous (s.c.) dose of 1.2 nmol/kg (body weight) insulin aspart (IAsp) or 1.2 nmol/kg human insulin (HI) during a euglycemic glucose clamp after overnight fast. Serum insulin and glucose concentrations were measured and the glucose infusion rate (GIR) was adjusted after dosing, to maintain blood glucose near basal levels. Individual model parameters were estimated for IAsp, HI, and the corresponding glucose and GIR data. We found statistically significant differences between most of the HI and IAsp pharmacokinetic parameters, including the sigmoidicity of the time course of absorption (1.5 for HI vs. 2.1 for IAsp (unit less), P = 0.0005, Wilcoxon Signed-rank test), elimination rate constant (0.010 min-1 for HI vs. 0.016 min-1 for IAsp (P = 0.002)). The PD model parameters were mostly not different, except for the rate of insulin action (0.012 min-1 for HI vs. 0.017 min-1 for IAsp (P = 0.03)). The model may provide a framework to account for different PK properties when estimating the PD properties of insulin and insulin analogues in glucose clamp experiments.

Gene therapy of streptozotocin-induced diabetes by intramuscular delivery of modified preproinsulin genes

BACKGROUND

Despite improvements in insulin preparation and delivery, physiological normoglycemia is not easily achieved in diabetics. Therefore, there has been considerable interest in developing gene therapy approaches to supply insulin. We studied a nonviral muscle-based method of gene therapy and demonstrated that it could prevent hyperglycemia in murine streptozotocin (STZ)-induced diabetes.

METHODS

A plasmid encoding mouse furin-cleavable preproinsulin II cDNA (FI), or its B10-analogue (B10FI), and a plasmid encoding furin were coinjected into muscle of CD-1 mice, who were treated a day later with STZ to induce diabetes. Electroporation was applied to increase gene transfer. Blood glucose was measured in fed and fasting mice, and fasting plasma insulin was measured by radioimmunoassay. The form of insulin produced and the presence of C-peptide were analyzed by gel filtration chromatography.

RESULTS

A B10FI plasmid codelivered with a furin plasmid reduced fed and fasting blood glucose levels in STZ-treated diabetic mice. The (pro)insulin levels in plasma were increased by up to 70-fold versus blank plasmid-treated diabetic mice. The administration of FI with furin was less effective. (Pro)insulin levels were greatly increased by using two plasmids carrying different promoter elements (CMV and SV40). Insulin was identified in muscle cells by immunohistochemistry. In plasma, 40-70% of the (pro)insulin was processed to the mature form and free C-peptide was identified. Insulin gene-treated mice had improved growth rates and appeared healthier. A single injection of B10FI with SV40Furin DNA increased plasma (pro)insulin for at least 8 weeks and reduced fed blood glucose levels for 5 weeks and fasting levels for 8 weeks.

CONCLUSIONS

This is the first report that electroporation-enhanced intramuscular gene therapy with B10FI can prevent hyperglycemia in murine STZ-induced diabetes. Gene therapy using various routes and methods of furin-cleavable insulin gene delivery has been previously explored but, in muscle, results comparable to ours have not been reported.

Clinical pharmacokinetics and pharmacodynamics of insulin aspart

Insulin aspart is a novel rapid-acting insulin analogue with improved subcutaneous absorption properties when compared with soluble human insulin. Pharmacokinetic studies show an absorption profile with a time to reach peak concentration (t(max)) about half that of human insulin, a peak plasma drug concentration (Cmax) approximately twice as high and shorter residence time. The potency and bioavailability of insulin aspart are similar to those of human insulin. The pharmacokinetics of insulin aspart have been studied in healthy Caucasian and Asian-Japanese volunteers, in patients with type 1 and 2 diabetes mellitus, and in children with diabetes, with both pre- and postprandial administration and during continuous subcutaneous insulin infusion (CSII). The pharmacokinetic profile was similar to that of another rapid-acting insulin analogue, insulin lispro, on the basis of published information for that agent. Pharmacodynamic studies show a smaller excursion of postprandial glucose with insulin aspart injected subcutaneously just before the meal compared with soluble human insulin injected 30 minutes before the meal in patients with type 1 diabetes mellitus, and an equivalent control in patients with type 2 diabetes displaying residual insulin production. In a treatment study, glucose excursions evaluated from 24-hour glucose profiles showed less variability with insulin aspart compared with human insulin. Adverse events, including hypoglycaemia-induced ventricular repolarisation and hypoglycaemic threshold and awareness, did not differ between insulin aspart and human insulin. The available data suggest that subcutaneous injections of insulin aspart just before meals better mimic the endogenous insulin profile in blood compared with human insulin, resulting in improved glucose control in a meal-related insulin regimen. This review summarises the clinical pharmacokinetics and pharmacodynamics of insulin aspart in relation to human insulin and insulin lispro.

Insulin aspart: promising early results borne out in clinical practice

The novel, rapid-acting insulin analogue insulin aspart (IAsp; Novo Nordisk) has been shown in preclinical studies to be more rapidly absorbed than human insulin (HI) when administered subcutaneously. IAsp reaches higher peak serum concentrations in a shorter time than HI, whilst maintaining a similar receptor binding and safety profile. The physiological pharmacokinetic profile of IAsp compared to that of HI has been demonstrated in both adult and paediatric populations and was accompanied by small but statistically significant reductions in HbA(1c), lower postprandial glucose excursions and a reduced risk of late postprandial and major nocturnal hypoglycaemia. Benefits may be maximised by dose optimisation, using bolus doses that result in effective postprandial glucose reduction, as well as higher and multiple basal insulin doses. The safety profile, including cardiovascular risk, is equivalent to HI.

Insulin analogues: have they changed insulin treatment and improved glycaemic control?

To improve insulin therapy, new insulin analogues have been developed. Two fast-acting analogues with a more rapid onset of effect and a shorter duration of action combined with a low day-to-day variation in absorption rate are now available. Despite this favourable time-action profile most studies have not been able to show any improvement in overall glycaemic control with the fast-acting analogues. A reduced post-prandial increase in blood glucose has been found in all studies, whereas between 3 and 5 h after the meal and during the night an increased blood glucose level is the normal course. This is probably the main explanation for the absence of improvement in overall glycaemic control when compared with regular human insulin. A tendency to a reduction in hypoglycaemic events during treatment with fast-acting analogues has been observed in most studies. Recent studies have indicated that NPH insulin administered several times daily at mealtimes can improve glycaemic control without increasing the risk of hypoglycaemia. The fast-acting analogues are now also available as insulin mixed with NPH. Insulin glargine is a new long-acting insulin which is soluble and precipitates after injection, resulting in a long half-life with a residual activity of about 50% 24 h after injection. Insulin glargine is a peakless insulin and studies in both type 1 and type 2 diabetic patients indicate that glargine improves fasting blood glucose control and reduces the incidence of nocturnal hypoglycaemia. Surprisingly, the new fast-acting analogues have not achieved the expected commercial success, which emphasises the need for new strategies for basal insulin supplementation, exercise, diet and blood glucose monitoring.

Graphical human insulin time-activity profiles using standardized definitions

The purpose of this study was to (1) develop consistent definitions to report time-activity profiles of insulin formulations, (2) determine human insulin time-activity profiles based on all available pharmacokinetic studies of biosynthetic human insulin rDNA(E. coli) (Humulin), and (3) create graphs that accurately and usefully represent human insulin time-activity profiles (TAPs). Standard definitions of onset, peak, duration, and time of 50% maximal activity were developed for human insulin. Results from all pharmacokinetic and pharmacodynamic studies available on human insulin from searches of both published literature and unpublished work were analyzed by these standard methods. Data obtained using these definitions were used to construct diagrams of the time-activity relationships for each formulation. Sixty-three insulin tests utilizing a variety of methodologies and data analysis techniques were located. Time-activity curves generated by application of standardized definitions varied depending on methodology, and on whether glucose, insulin and/or glucose infusion rates were used as the measure of insulin activity. A method of standard analysis is required for evaluating insulin pharmacokinetic studies due to the wide variation in design of these studies. Graphic representation of ranges obtained by standard analysis of onset, peak, duration, and 50% maximal activity increase the information transmitted when compared to currently used tables of time-activity data. The time of 50% maximal activity during increasing and decreasing phases may be a better marker of clinically significant activity than the classically defined parameters of onset and duration.

Efficacy, safety, and pump compatibility of insulin aspart used in continuous subcutaneous insulin infusion therapy in patients with type 1 diabetes

OBJECTIVE

The purpose of this study was to compare the efficacy, safety and pump compatibility of insulin aspart (a rapid-acting insulin analog) and buffered regular human insulin in patients with type 1 diabetes undergoing continuous subcutaneous insulin infusion (CSII) therapy.

RESEARCH DESIGN AND METHODS

This was a single-center randomized open-label study Patients received CSII therapy with insulin aspart (n = 19) or buffered regular human insulin (n = 10) for 7 weeks. Bolus doses of insulin aspart were administered immediately before meals and buffered regular human insulin 30 min before meals.

RESULTS

Insulin aspart and buffered regular human insulin were both effective in controlling average daily blood glucose levels (8.2 +/- 1.9 and 8.5 +/- 2.1 mmol/l, respectively) (mean +/- SD) and maintaining serum fructosamine (343 +/- 25.7 and 336 +/- 27.4 micromol/l) and HbA1c (6.9 +/- 0.6 and 7.1 +/- 0.6%) levels. Possible obstructions and set leakages were infrequently reported in both groups. Similar numbers of patients experienced hypoglycemia (blood glucose <2.5 mmol/l): 14 (74%) insulin aspart patients versus 6 (60%) buffered regular human insulin patients. Patients receiving insulin aspart had fewer hypoglycemic events per patient (2.9) than those patients receiving buffered regular human insulin (6.2). There were no differences between the two insulins in the occurrence of hyperglycemic events (blood glucose >19 mmol/l) or in the number and type of adverse events.

CONCLUSIONS

Insulin aspart and buffered regular human insulin were effective and well tolerated and provided similar pump compatibility when used in CSII therapy.

Insulin aspart: a new rapid-acting insulin analog

OBJECTIVE

To examine the pharmacology, therapeutics, pharmacokinetics, dosing guidelines, adverse effects, and drug interactions of insulin aspart, and summarize the clinical trials of efficacy and safety in patients with type or type 2 diabetes mellitus.

DATA SOURCES

A MEDLINE database search (1985-May 2000) was performed to identify all applicable published articles and abstracts; in some cases, Novo Nordisk unpublished information was also obtained. Review articles on insulin analogs were also identified, as well as review chapters in medical textbooks.

STUDY SELECTION

The majority of the studies identified were in abstract form. These studies reported information on the pharmacokinetics of insulin aspart in healthy volunteers and in those with diabetes, as well as the therapeutic utility, safety, and clinical efficacy in patients with diabetes. A limited number of randomized studies were reported as artices in the medical literature

DATA EXTRACTION

All published clinical studies were reviewed.

DATA SYNTHESIS

Insulin aspart, the second Food and Drug Administration-approved rapid-acting insulin analog, is produced by recombinant technology that replaces the proline at position 28 on the B chain of insulin with negatively charged aspartic acid. Insulin aspart exists as hexamers that rapidly dissociate into monomers and dimers on subcutaneous injection. When administered immediately prior to a meal, insulin aspart is at least as effective as regular human insulin in control of postprandial blood glucose concentrations. Insulin aspart achieves higher peak insulin concentrations in less time and with a shorter duration of action than regular human insulin.

CONCLUSIONS

Insulin aspart is a convenient premeal insulin for use by patients requiring mealtime insulin. Furthermore, due to favorable pharmacokinetics, insulin aspart controls postprandial blood glucose concentrations at least as well as regular human insulin and contributes to improved quality of life.

Four new monomeric insulins obtained by alanine scanning the dimer-forming surface of the insulin molecule

The residues A21Asn, B12Val, B16Tyr, B24Phe, B25Phe, B26Tyr and B27Thr, buried in the dimer of insulin, were identified by means of alanine-scanning mutagenesis. The receptor binding activity, in vivo biological potency and self-association properties of the seven single alanine human insulin mutants were determined. Four of the seven single alanine mutants, [B12Ala]human insulin, [B16Ala]human insulin, [B24Ala]human insulin and [B26Ala]human insulin, are monomeric insulin, which indicates that B12Val, B16Tyr, B24Phe and B26Tyr are crucial for the formation of insulin dimer. The monomeric [B16Ala]human insulin and [B26Ala]human insulin retain 27 and 54% receptor binding activity, respectively, and nearly the same in vivo biological potency compared with native insulin, so they could be developed as the fast-acting insulin.

Pharmacokinetics and pharmacodynamics of insulin aspart, a rapid-acting analog of human insulin, in healthy Japanese volunteers

Pharmacokinetic and pharmacodynamic properties of a rapid-acting analog of human insulin, insulin aspart, were compared with those of soluble human insulin in Japanese healthy subjects. Subcutaneous single injections (0.025 and 0.05 U/kg body weight (BW)) of insulin aspart produced a significantly earlier peak of exogenous insulin level in comparison with human insulin (30.8+/-13.8 versus 61.3+/-14. 6 min, P<0.9001 for 0.025 U/kg; and 39.2+/-18.8 versus 99.2+/-53.8 min, P<0.005 for 0.05 U/kg). The peak serum level of insulin aspart was higher than that of human insulin (23.0+/-6.0 versus 9.9+/-3.1 microU/ml for 0.025 U/kg; and 30.9+/-9.2 versus 13.3+/-4.1 microU/ml for 0.05 U/kg, P<0.0001). The time to the minimal level of glucose after insulin aspart was significantly shorter compared with human insulin (P<0.05 for 0.025 U/kg BW and P<0.01 for 0.05 U/kg BW). The Delta change in blood glucose induced by insulin aspart was larger than that observed for human insulin at any dose (P<0.001). The repeated injection of insulin aspart before each meal also resulted in a rapid rise in exogenous insulin level with peak level obtained approximately 40 min after insulin aspart at any dose. When compared with results of other trials with insulin aspart, the present results showed that pharmacokinetic and pharmacodynamic profiles of the rapid-acting analog insulin aspart in Japanese subjects are no different from those in nonJapanese subjects.

Models of subcutaneous insulin kinetics. A critical review

Subcutaneous insulin kinetics is a complex process whose quantitation is needed for a reliable glycemic control in the conventional therapy of insulin-dependent diabetes. The major difficulties in modeling include accounting for the distribution in the subcutaneous depot and transport to plasma. A single model describing in detail the various processes for all the commercially available insulin preparations is not available. Several models however have been proposed which vary in the degree of complexity. Virtually all of them handle the regular insulin preparation while a few handle the intermediate acting and the novel insulin analogues. In this paper we critically review these models.

Lymphatic transport of proteins after subcutaneous administration

This mini-review summarizes the relevant literature regarding the lymphatic transport of proteins after subcutaneous administration. A review of the physiology of the lymphatics and inherent anatomical differences between blood and lymph capillaries is presented followed by a brief overview of the general characteristics of protein absorption and bioavailability following S.C. injection. A description of factors known to directly affect the lymphatic uptake of macromolecules follows and is supported by representative data from this laboratory. A brief perspective on the importance of lymphatic uptake and transport in understanding the biopharmaceutical properties of protein drugs and potentially targeting the lymphatics is presented.

Insulin delivery with plasmid DNA

Success in controlling hyperglycemia in type I diabetics will require a restoration of basal insulin. To this end, three plasmid DNAs (pDNA) encoding preproinsulin were compared for constitutive expression and processing to insulin in nonendocrine cells in vitro. The pDNAs were designed to express rat proinsulin I (VR-3501), rat proinsulin I with the B10 aspartic acid point mutation (VR-3502), and a derivative of VR-3502 with a furin cleavage site added at the B-chain and C-peptide junction (VR-3503). Cells transfected with VR-3501 or VR-3502 were able to secrete only proinsulin, whereas transfection with VR-3503 yielded 30-70% mature insulin, which could be increased to >99% by cotransfection with a furin expression plasmid (VR-3505). The insulin produced was biologically active. The bilateral injection of 100 microg of VR-3502 plasmid into the tibialis anterior muscles of mice on two consecutive days yielded, on average, several hundred picograms of heterologous proinsulin per milliliter of serum. In BALB/c mice, serum proinsulin peaked 7-14 days postinjection and declined to preinjection levels by days 21-28. In athymic nude mice, serum proinsulin was sustained for at least 6 weeks. The therapeutic efficacy of delivering insulin via muscle injection of pDNA was evaluated in athymic nude mice made diabetic with the beta cell toxin streptozotocin (STZ). All animals given control DNA died within 1 week of receiving STZ while 40% of the mice coinjected with plasmids VR-3503 and VR-3505 lived through the duration of the 4-week experiment. Muscles of the surviving animals contained 17-100 ng of immune-reactive insulin (IRI), 86-94% of which was mature insulin. The results suggest that heterologous insulin made in muscle increased the survival rate. We propose that insulin plasmid expression in skeletal muscle may be a valid approach to basal insulin delivery. The feasibility of plasmid DNA-based delivery of basal insulin was investigated. An expression system consisting of pDNAs encoding a selectively mutated rat preproinsulin and mouse furin was developed and characterized in vitro and in vivo. When injected with preproinsulin pDNA, the mouse tibialis anterior muscle expressed and released proinsulin into serum at levels comparable to normal basal insulin in rodents. These heterologous proinsulin levels were sustained for several weeks in immune-compromised nondiabetic mice. Mouse muscle coinjected with a pDNA encoding the endopeptidase furin and a pDNA encoding a pre-proinsulin modified to contain two furin cleavage sites produced fully processed insulin. This muscle-made insulin appears to have contributed to the survival of mice treated with a highly diabetogenic dose of streptozotocin, a beta cell toxin. The results demonstrate that skeletal muscle is able to express and deliver therapeutic insulin from plasmid DNA.

Hypoglycemia and insulin analogues: is there a reduction in the incidence?

Rapid-acting insulin analogues were developed in answer to the need for a more appropriate time-action profile for prandial insulin substitution therapy. Improvements in at least one of three important endpoints needs to be demonstrated-metabolic control, hypoglycemic events, and/or quality of life-if there is to be a case for use of a new insulin preparation. This paper considers the data available on hypoglycemic events in the 24 controlled clinical trials (19 open, unblinded, and 5 double-blind) reported to date with rapid-acting insulin analogues (22 studies with insulin lispro). A significant reduction in the incidence of mild hypoglycemia was observed in 5 of 22 studies (22%). No change in frequency of severe hypoglycemic episodes was observed 10 of 12 studies (83%) reporting such events. A decrease in the frequency of nocturnal hypoglycemia has been reported in six studies; however, in the other 18 studies, no similar decrease in numbers were reported. There is no evidence for a reduction in patient awareness of hypoglycemia with rapid-acting insulin analogues. Even a slight reduction in hypoglycemic events would be welcomed by diabetic patients. However, rapid-acting insulins are only appropriate for use in patients using an intensive insulin regimen. Such patients are well motivated and well educated and will be able to adapt their insulin therapy to take account of the changes in the time-action profile of the rapid-acting insulin analogues. Thus, rapid-acting insulin analogues do not appear to have revolutionized insulin therapy, but appropriate use should result in benefits such as improved metabolic control for diabetic patients.

Insulin analogs with improved pharmacokinetic profiles

The aim of insulin replacement therapy is to normalize blood glucose in order to reduce the complications of diabetes. The pharmacokinetics of the traditional insulin preparations, however, do not match the profiles of physiological insulin secretion. The introduction of the rDNA technology 20 years ago opened new ways to create insulin analogs with altered properties. Fast-acting analogs are based on the idea that an insulin with less tendency to self-association than human insulin would be more readily absorbed into the systemic circulation. Protracted-acting analogs have been created to mimic the slow, steady rate of insulin secretion in the fasting state. The present paper provides a historical review of the efforts to change the physicochemical and pharmacological properties of insulin in order to improve insulin therapy. The available clinical studies of the new insulins are surveyed and show, together with modeling results, that new strategies for optimal basal-bolus treatment are required for utilization of the new fast-acting analogs.

Site-specific insulin conjugates with enhanced stability and extended action profile

Two different hydrophilic moieties, carboxyl derivatives of monosaccharidic (Glc, Gal, Man, Fuc) glycosides and methoxypolyethylene glycols of varying MW, were covalently attached to the insulin GlyA1, PheB1 and/or LysB29 amino groups (seven possible derivatives), and resulting insulin conjugates purified to homogeneity. In vivo bioactivity in rats of most derivatives was preserved while disubstituted PEG-insulins showed decreased potency. Only site-specific modification of PheB1 amino group with either moiety resulted in pronouncedly increased resistance of insulin to fibrillation, indicating that the B-chain N-terminus of the insulin molecule is mechanistically involved in the fibrillation process. Immunogenicity in vivo and in vitro of monoglycosylated insulins was comparable to that of insulin, diglycosylated insulins showed immunogenicity enhancement. Immunogenicity of PEG-insulins was significantly suppressed. PheB1-glycosylated insulins administered subcutaneously in dogs displayed extended action profiles, the most effective being PheB1-galactosylated insulin, resembling the pharmacodynamic response of intermediate-acting insulin preparations. The pharmacokinetic parameters of these insulin derivatives were not significantly different from that of insulin even though absorption and residence time and clearance were increased, providing some explanation for prolonged action profile. Lectin-specific binding as a retardation basis is not likely involved. In support of this, subcutaneously administered PheB1-PEG(600)-insulin showed an even more protracted action profile, suggesting that the basis of retardation is physical and nonspecific. This implies that by increasing PEG chain MW, further delay/prolongation of action can be achieved to yield new soluble basal insulin substitutes with potential clinical applications.

A sedimentation equilibrium study of platypus insulin: the HB10D mutant does not associate beyond dimer

An extensive study of the self-association patterns of zinc-free synthetic native and mutant (HB10D) platypus insulin in solution (pH = 7.0; I = 0.1 M; 25 degrees C) has been undertaken using the method of sedimentation equilibrium. The data was fitted to a mathematical equation describing the indefinite duoisodesmic (IDI) model of self-association [A.E. Mark, P.D. Jeffrey, Biol. Chem. Hoppe-Slayer, 371 (1990) 1165]. From this the relevant association constants, KA and KB, describing the polymerising system were calculated. This information allows the calculation of the complex distribution of odd and even numbered polymeric species within the insulin system in solution. In the studies on the self-association of the synthetic native and mutant platypus insulin, each was compared with bovine insulin as well as with each other. It is concluded that there is some reduction in the extent of the self-association of native platypus insulin compared to bovine insulin. A reduction, in specifically the dimer-dimer interaction, is indicated by the higher KA and lower KB values. HB10D platypus insulin shows a dramatic reduction in self-association compared to native platypus and to bovine insulin. Analysis of the self-association pattern yielding a KB value of effectively zero suggests that the substitution of an aspartic acid residue for a histidine at B10 virtually abolishes its dimer-dimer interaction. Platypus insulin has essentially the same biological activity as that of porcine (submitted for publication) but a somewhat lower self-association, while the introduction of one amino acid in a critical region increases the activity twofold while abolishing self-association beyond dimer.

Long-term comparison of human insulin analogue B10Asp and soluble human insulin in IDDM patients on a basal/bolus insulin regimen

Recombinant DNA technology allows the production of insulin analogues with faster absorption rates from subcutaneous tissue as compared to soluble human insulin. The human insulin analogue B10Asp (mono/dimeric) is absorbed twice as fast as soluble human insulin (hexameric). A double blind, randomised crossover study with a 1-month run-in period and two 2-month treatment periods was performed in 21 male insulin-dependent diabetic (IDDM) patients aged 18-40 years in order to compare the metabolic control obtained with equimolar doses of the analogue B10Asp vs soluble human insulin (Actrapid) given as mealtime insulin and intermediate acting isophane insulin (Protaphane) at bedtime. At the end of each 2-month study period, the patients were admitted to the metabolic ward. We found significantly higher plasma insulin/analogue levels after breakfast, lunch and dinner with B10Asp as compared to Actrapid (p < 0.05). The plasma insulin/analogue levels were significantly lower before lunch and dinner with B10Asp as compared to Actrapid (p < 0.05). Also, the plasma insulin/analogue level tended to be lower at bedtime when comparing B10Asp to Actrapid. The 24-h blood glucose profiles showed identical fasting blood glucose, significantly lower blood glucose after breakfast with the analogue (p < 0.05), no differences in blood glucose after lunch and dinner but a significantly higher blood glucose at midnight using the analogue (p < 0.05). The overall 24-h mean blood glucose concentrations, the daily insulin dose, HbA1c, diet, home blood glucose monitoring and frequency of hypoglycaemia were almost identical in the two treatment periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant-DNA-derived insulin analogues as potentially useful therapeutic agents

Whilst insulin is a spectacularly successful drug for the management of diabetes mellitus, it remains difficult to mimic the physiological pattern of insulin secretion, even using the various quick-acting and insoluble formulations that are available. The introduction of recombinant-DNA technology to the manufacture of therapeutic insulin has made the rational design and production of insulin analogues with altered pharmacokinetic and pharmacological properties possible. Such analogues include 'monomeric' insulins, which do not form the insulin-zinc hexamer in solution and are absorbed more rapidly from the injection site, and long-acting insulins, which are absorbed very slowly at physiological pH. Many of these analogues are being tested clinically, and it is possible that the next generation of insulin therapy will be various combinations of rationally designed insulin analogues produced by industrial biotechnology.

Conventional and sprinkler needle injection of magnesium insulin

Currently available short-acting insulin preparations fail to mimic the postprandial insulin profile of non-diabetic individuals. The activity of a novel insulin designed for faster absorption has been tested after subcutaneous injection. Magnesium insulin (50 U ml-1) given by sprinkler needle was compared with unmodified human insulin (100 U ml-1) given by conventional needle and unmodified human insulin (50 U ml-1) given by sprinkler needle in normal volunteers using a euglycaemic clamp. Magnesium insulin had a significantly faster onset of action resulting in a higher exogenous insulin level by 15 min, peak level was reached after 60 min compared with 75 min for the unmodified insulins, and duration of action was significantly shorter than both unmodified insulins. No significant differences were observed between the unmodified insulins for the first 5 h after injection, indicating that the observed differences to magnesium insulin could not be attributed to the insulin concentration or the type of needle used for insulin administration. Injection of magnesium insulin prior to a test breakfast in people with Type 2 diabetes resulted in significantly lower total and 0 to 120 min areas under the glucose curve, an earlier rise in exogenous insulin levels and a higher area under the insulin curve from 0 to 120 min compared with unmodified 100 U ml-1 human insulin.