Intensive therapy with inhaled insulin via the AERx insulin diabetes management system: a 12-week proof-of-concept trial in patients with type 2 diabetes

Solid lipid nanoparticles: a promising tool for insulin delivery

INTRODUCTION

Insulin plays a critical role in metabolism modulation including carbohydrate, lipid, and protein metabolism. There is room to improve insulin delivery but optimizing the best carrier remains challenging. Traditional and conventional approaches for insulin delivery do not emulate the normal fate of insulin release in the body. Despite extensive research attempts to overcome this and other challenges, the goal of achieving optimal insulin delivery that emulates the natural system remains unresolved.

AREAS COVERED

Solid Lipid Nanoparticles (SLNs) may provide a solution, because they are nontoxic, biocompatible, and straightforward to formulate thus providing a promising platform for achieving targeted and controlled delivery of various therapeutic agents. This review aims to provide an overview on the suitability and application of SLNs for insulin delivery. A special emphasis is placed on the biopharmaceutical aspects of insulin loaded SLNs which have not been explored in detail to date.

EXPERT OPINION

SLNs have proven to be safe and versatile drug delivery systems suitable for insulin delivery and capable of improving the efficacy and pharmacokinetic profile of encapsulated insulin. There is still some work to be done to fully explore SLNs' true potential as drug delivery and specifically insulin delivery vehicles suitable for clinical use.

Therapeutic peptides for the treatment of cystic fibrosis: Challenges and perspectives

Cystic fibrosis (CF) is the most common amongst rare genetic diseases, affecting more than 70.000 people worldwide. CF is characterized by a dysfunctional chloride channel, termed cystic fibrosis conductance regulator (CFTR), which leads to the production of a thick and viscous mucus layer that clogs the lungs of CF patients and traps pathogens, leading to chronic infections and inflammation and, ultimately, lung damage. In recent years, the use of peptides for the treatment of respiratory diseases, including CF, has gained growing interest. Therapeutic peptides for CF include antimicrobial peptides, inhibitors of proteases, and modulators of ion channels, among others. Peptides display unique features that make them appealing candidates for clinical translation, like specificity of action, high efficacy, and low toxicity. Nevertheless, the intrinsic properties of peptides, together with the need of delivering these compounds locally, e.g. by inhalation, raise a number of concerns in the development of peptide therapeutics for CF lung disease. In this review, we discuss the challenges related to the use of peptides for the treatment of CF lung disease through inhalation, which include retention within mucus, proteolysis, immunogenicity and aggregation. Strategies for overcoming major shortcomings of peptide therapeutics will be presented, together with recent developments in peptide design and optimization, including computational analysis and high-throughput screening.

Preclinical Safety Assessment of 2 Inhaled Single-Domain Antibodies in the Cynomolgus Monkey

The safety of 2 single domain antibodies (dAbs) was evaluated by inhalation toxicology studies in the cynomolgus monkey. In the first case study, a 14-day repeat-dose study evaluating an anti-thymic stromal lymphopoietin (anti-TSLP) dAb resulted in minimal mononuclear inflammatory cell infiltrates in the lungs, increases in lymphocytes in bronchoalveolar lavage fluid, and development of antidrug antibodies (ADAs). In a 6-week inhalation study, there was an increase in incidence and/or severity of mononuclear cell infiltrates in the lung, increased cellularity in the tracheobronchial lymph node (TBLN), and development of ADA. The second case study evaluated a change in duration of inhalation dosing, a different route of exposure (intravenous or IV), and recovery following an off-dose period with an anti-tumor necrosis factor receptor 1 dAb. A 7-day repeat-dose inhalation study and a 14-day IV study produced no microscopic effects in the lung, whereas a 14-day inhalation study resulted in moderate increases in pulmonary perivascular/peribronchiolar/alveolar lymphocytic infiltrates and increased cellularity in the TBLN, with partial and full recovery, respectively, after 14 days. The lung and lymph node findings seen after inhalation of either dAb were considered secondary to the immunogenic response to a human protein and were considered nonadverse.

Clinical Pharmacology of Fast-Acting Insulin Aspart Versus Insulin Aspart Measured as Free or Total Insulin Aspart and the Relation to Anti-Insulin Aspart Antibody Levels in Subjects with Type 1 Diabetes Mellitus

Background

Fast-acting insulin aspart (faster aspart) is an ultra-fast-acting formulation of insulin aspart (IAsp). This post hoc analysis investigated the pharmacokinetics of faster aspart versus IAsp, measured as free or total IAsp, and the relationship between anti-IAsp antibodies and the pharmacokinetics/pharmacodynamics of faster aspart and IAsp.

Methods

Free and total IAsp concentrations and anti-IAsp antibodies were determined in adults with type 1 diabetes mellitus receiving subcutaneous faster aspart and/or IAsp in four single-dose clinical pharmacology trials (n = 175) and a 26-week phase IIIa trial (n = 1040). Pharmacodynamics were assessed by euglycaemic clamp or meal test, respectively.

Results

The pharmacokinetic profile was left-shifted and early exposure was greater with faster aspart versus IAsp independent of free or total IAsp assay. The faster aspart-IAsp difference in the time to 50% of maximum IAsp concentration in the early part of the pharmacokinetic profile (t_{Early 50 % Cmax}) [95% confidence interval (CI)] was − 8.8 [− 10.0 to − 7.5] and − 7.6 [− 8.8 to − 6.4] min for free and total IAsp, respectively. The faster aspart/IAsp ratio for the area under the concentration–time curve (AUC) for IAsp from time zero to 30 min (AUC_{IAsp,0–30 min}) [95% CI] was 1.88 [1.74–2.04] and 1.77 [1.64–1.90] for free and total IAsp. Higher anti-IAsp antibody levels were associated with a lower ratio of free/total IAsp for the total AUC for IAsp (AUC_IAsp,0–t). Early glucose-lowering effect (AUC for the glucose infusion rate [GIR] from time zero to 60 min [AUC_{GIR,0–60 min}]) was greater by 25–44% for faster aspart versus IAsp independent of anti-IAsp antibody levels. Total glucose-lowering effect (total AUC for GIR [AUC_GIR,0–t]) in a clamp and 1-h postprandial glucose increment in a meal test appeared essentially unaffected by anti-IAsp antibodies.

Conclusions

Faster aspart provides accelerated pharmacokinetics versus IAsp regardless if based on free or total IAsp assay. Higher anti-IAsp antibodies increase total IAsp concentrations but do not influence faster aspart nor IAsp pharmacodynamics.

ClinicalTrials.gov identifiers

NCT01618188, NCT02003677, NCT01934712, NCT02568280, NCT01831765.

Electronic supplementary material

The online version of this article (10.1007/s40262-018-0718-6) contains supplementary material, which is available to authorized users.

Exogenous insulin antibody syndrome (EIAS): a clinical syndrome associated with insulin antibodies induced by exogenous insulin in diabetic patients

Insulin has been used for diabetes therapy and has achieved significant therapeutic effect. In recent years, the use of purified and recombinant human insulin preparations has markedly reduced, but not completely suppressed, the incidence of insulin antibodies (IAs). IAs induced by exogenous insulin in diabetic patients is associated with clinical events, which is named exogenous insulin antibody syndrome (EIAS). The present review is based on our research and summarizes the characterization of IAs, the factors affecting IA development, the clinical significance of IAs and the treatments for EIAS.

Review: Current status of the development of inhaled insulin

The most promising alternative route of insulin administration seems to be pulmonary delivery by inhalation. For a maximal rate of absorption insulin must be applied deep into the lung, i.e., into the alveoli. A number of inhalers designed to generate an aerosol with an appropriate particle size for pulmonary delivery are currently in clinical development. The pharmacodynamic effects of insulin formulations administered via the lung are comparable to, or are even faster than, those of subcutaneously injected regular insulin or rapid-acting insulin analogues. The relative biopotency of inhaled insulin is approximately 10%, i.e., the dose of inhaled insulin must be 10 times higher than the dose applied subcutaneously in order to induce a comparable metabolic effect. Clinical trials indicate that metabolic control with this pain free route of insulin administration is at least comparable to that of subcutaneous (sc) insulin therapy. Side effects. observed in human trials, gave rise to safety concerns that have delayed development for several years. Nevertheless, recent long-term safety studies indicate that the increased stimulation of insulin antibody formation stopped after some time and that the observed changes in lung function were minor or reversible. Consequently the first application for an approval of pulmonary insulin has been submitted to the authorities. In summary, it seems as if, after several decades of research, for the first time a feasible alternative route for insulin administration is within Reach.

Review: Diabetes and insulin therapy in older people

Concerns about hypoglycaemia, plus lack of evidence of benefit, contributed to underutilisation of insulin for older people with type 2 diabetes in the past. Following the UKPDS it is clear that many elderly patients treated with diet and oral antidiabetic agents will develop beta-cell failure and will be at risk of worsening glycaemic control with reduced well-being unless insulin is considered. Following diabetes diagnosis, the mainstay of treatment will be dietary control and exercise together with management of cardiovascular risk factors. When glycaemic control deteriorates oral agents will be needed. However, whereas in the past insulin was seen as a last resort for older type 2 patients there is support for considering its early use in selected older people with preserved cognitive function and poor glycaemic control, as well as for frail older people with weight loss and poor quality of life. The regimens of choice may include a combination of basal insulin with oral agents or twice-daily combinations of premixed short and intermediate acting insulin. The development of insulin analogues with their associated reduced risk of hypoglycaemia may also herald a new era of insulin treatment for older people.

Review: Inhaled insulin: overcoming barriers to insulin therapy?

nhaled insulin is a new route of insulin delivery that can be used in the treatment of type 1 and type 2 diabetes. It offers an alternative and additional means of insulin administration, and has been received with particular satisfaction by patients who dislike injections. Trials indicate that inhaled insulin can be used effectively for pre-meal bolus intensification of treatment. Pre-meal inhaled insulin with Exubera® has shown faster absorption and similar duration of action to regular subcutaneous insulin with an overall similar glucodynamic effect. Although bioavailability is lower, mainly due to losses in the upper airways, this is compensated for by dose. The commonest side effect reported with inhaled insulin, as with subcutaneous insulin, was hypoglycaemia, almost a quarter of patients noted a cough which settled with continued treatment. Increased antibody titres and changes in lung function return to normal on discontinuation of inhaled insulin. Quality of life scores indicate patient preference for inhaled versus injected insulin, thus increased choice may improve adherence to treatment regimens. However, true cost:benefit analyses have to be undertaken as do studies in children, smokers and people with respiratory conditions, e.g. asthma.

Immunogenicity of Biotherapeutics: Causes and Association with Posttranslational Modifications

Today, potential immunogenicity can be better evaluated during the drug development process, and we have rational approaches to manage the clinical consequences of immunogenicity. The focus of the scientific community should be on developing sensitive diagnostics that can predict immunogenicity-mediated adverse events in the small fraction of subjects that develop clinically relevant anti-drug antibodies. Here, we discuss the causes of immunogenicity which could be product-related (inherent property of the product or might be picked up during the manufacturing process), patient-related (genetic profile or eating habits), or linked to the route of administration. We describe various posttranslational modifications (PTMs) and how they may influence immunogenicity. Over the last three decades, we have significantly improved our understanding about the types of PTMs of biotherapeutic proteins and their association with immunogenicity. It is also now clear that all PTMs do not lead to clinical immunogenicity. We also discuss the mechanisms of immunogenicity (which include T cell-dependent and T cell-independent responses) and immunological tolerance. We further elaborate on the management of immunogenicity in preclinical and clinical setting and the unique challenges raised by biosimilars, which may have different immunogenic potential from their parent biotherapeutics.

Pure insulin highly respirable powders for inhalation

The aim of the present research was to investigate the possibility to obtain by spray drying an insulin pulmonary powder respirable and stable at room temperature without the use of excipients. Several insulin spray-dried powders were prepared with or without the addition of excipients (mannitol, bovine serum albumin, aspartic acid) from water dispersions or from acidic aqueous solutions. Each formulation was characterized using laser diffraction, scanning electron microscopy and in vitro aerosol performance with a Turbospin DPI device. Stability was assessed by the quantification of impurities with a molecular mass greater than that of insulin (HMWP) and related proteins (A21+ORP). Insulin powders prepared without excipients from an acid solution showed a shrivelled, raisin-like shape of non-aggregated microparticles and a high respirability (FPF>65%). The optimal result with respect to respirability and stability was reached when the pH of the insulin acetic acid solution to spray dry was adjusted at pH 3.6 with ammonium hydroxide. The median volume diameter of the obtained powder was 4.04 μm, insulin content 95%, emitted dose of 89.5%, MMAD 1.79 μm and fine particle fraction of 83.6%. This powder was stable at room temperature over a period of eighteen months with respect to the content of A21+ORP. As far as the HMWP content was concerned, the powder complied with the specification limits for a period of five months. The insulin acetic powder opens up the possibility of a more effective pulmonary therapy less dependent on refrigerated storage.

Novel non-invasive methods of insulin delivery

INTRODUCTION

Insulin has usually been administered subcutaneously in the treatment of diabetes mellitus. Alternative delivery routes of insulin are expected to overcome some limitations, mainly concerned with the possibility of hypoglycemia episodes, weight gain and inadequate post-meal glucose control, in order to lead a better patient compliance.

AREAS COVERED

This review article covers all the most relevant non-invasive insulin delivery methods under development, respective technology and clinical data available according to their status of development. Special focus is given to the systems with late clinical trial evidences, their achievements and pitfalls. Pulmonary and oral appear to be the most advantageous routes, with regard to the long list of potentially marketed products.

EXPERT OPINION

Alternative insulin delivery to the subcutaneous administration is more and more close to the success, being fundamental that any optimized technology could overcome the overall low mucosal bioavailability of insulin, mostly due to its early degradation before absorption, inactivation and digestion by proteolytic enzymes and poor permeability across mucosal epithelium because of its high molecular weight and lack of lipophilicity.

Can inhaled insulin be used for the treatment of diabetes mellitus?

Reluctance to start and adequately titrate subcutaneous insulin are major reasons why many patients with diabetes mellitus are insufficiently metabolically controlled. Pulmonary insulin administration has the advantage over subcutaneous insulin in that it is noninvasive, seems better accepted by the diabetic population and exerts equal efficacy in terms of glycemic control. As such, inhaled insulin has the potential to increase the diabetic (Type 2) patient's willingness to commence and adhere to insulin therapy. Inhaled insulin's short duration of action makes it suitable for prandial administration provided that basal insulin requirements are met by residual b-cell function, or by supplemental long-acting subcutaneous insulin. In clinical trials, inhaled insulin is comparable to short-acting subcutaneous insulin with regard to efficacy and hypoglycemic risk. Adverse effects associated with inhaled insulin include dry cough, which tends to diminish over time, a slight drop in pulmonary function that does not progress and is reversible in most patients if treatment is discontinued, and increased insulin antibody formation, albeit without clinical sequelae. Long-term safety remains an issue for a product intended to be used chronically for many years. Exubera((R)) was thus far the only inhaled insulin product to receive approval in the USA and Europe for use in adults with Type 1 or Type 2 diabetes, but was recently withdrawn from the market. At present it is unclear how this decision will affect programs from other companies with inhaled insulin products under development.

In pursuit of excellence in diabetes care: trends in insulin delivery

Diabetes mellitus has been estimated to affect 2.9 million people in the UK. Large-scale clinical trials conclusively demonstrate that elevated blood glucose levels are associated with an increased risk of micro- and macrovascular complications. The high rates of morbidity and mortality associated with this condition demonstrate how important effective glycaemic control is. Subcutaneous insulin injection continues to be the mainstay of therapy for all people with type 1 diabetes mellitus and the majority of individuals with type 2 diabetes mellitus. However, there are a number of barriers to insulin therapy. For example, conventional insulin delivery is arguably time consuming. Furthermore, it has been associated with common errors, such as inaccurate dosing and administration (National Patient Safety Agency, 2010). Insulin pen devices have various advantages over conventional delivery. Their ease of use and incorporation into busy lifestyles may improve diabetes control with much less effort, while maintaining adherence and quality of life. Research in insulin delivery shows there is a prospect of needle-free delivery in the near future. Despite such progress, the role of the healthcare professionals in involving, assessing, supporting and educating people having insulin therapy, including the attainment of the agreed blood glucose levels, cannot be overestimated.

The economic and clinical benefits of adequate insulin initiation and intensification in people with type 2 diabetes mellitus

AIM

To study the clinical and economic benefits associated with adequate and early initiation and intensification of insulin in people with type 2 diabetes mellitus (T2DM).

METHODS

A systematic review was performed using published articles from January 2000 to August 2010 that linked intervention, disease, study design and outcomes. Studies were further classified as initiation and intensification based on predefined criteria. Individual studies in systematic reviews and meta-analysis were searched and included if relevant.

RESULTS

A total of 2690 articles were screened with 76 (40 initiation and 36 intensification) studies included. Most initiation studies had mean baseline HbA1c values of >8.5%. The endpoint HbA1c values were reduced with insulin treatment in these studies, with endpoint values ranging from 6.6 to 9.8%. Similar results were seen with the intensification studies (endpoint HbA1c: 6.4-9.6%). Addition of insulin to oral antidiabetics (OADs) resulted in better glycaemic control in most studies. Blood glucose levels reduced substantially with OADs + insulin compared with OADs alone. Quality of life outcomes and treatment satisfaction were reported in six studies and not significantly different for insulin vs. OADs. Hypoglycaemic events were manageable with insulin initiation. However, all insulin types were associated with weight gain although the comparison with OADs elicited varying results.

CONCLUSIONS

Proactive management with early insulin initiation and intensification should be considered in people with T2DM in inadequate glycaemic control. The economic benefits with early initiation and intensification have to be fully explored.

Inhaled insulin: too soon to be forgotten?

Inhalation is a potentially viable route of administration for numerous agents. In diabetes mellitus, the need for frequent injections to achieve ideal glycemic control remains a significant limitation for initiating and complying with insulin therapy in a large number of patients. To overcome this barrier, inhaled insulin was developed. The inhalation form of regular human insulin has been tested and administered in a large number of trials. Respiratory capacity was evaluated in patients with normal lung parenchyma in whom inhaled insulin was administered without complications. However, issues like cost, bulky device, fear for lung safety, and the small number of studies in subjects with underlying respiratory disease prevented widespread use of this new mode of delivery. In the present review, we will suggest a number of methods that could be applied in this form of administration to maximize drug absorption and fully exploit the advantages of this route of administration.

Impact of product-related factors on immunogenicity of biotherapeutics

All protein therapeutics have the potential to be immunogenic. Several factors, including patient characteristics, disease state, and the therapy itself, influence the generation of an immune response. Product-related factors such as the molecule design, the expression system, post-translational modifications, impurities, contaminants, formulation and excipients, container, closure, as well as degradation products are all implicated. However, a critical examination of the available data shows that clear unequivocal evidence for the impact of these latter factors on clinical immunogenicity is lacking. No report could be found that clearly deconvolutes the clinical impact of the product attributes on patient susceptibility. Aggregation carries the greatest concern as a risk factor for immunogenicity, but the impact of aggregates is likely to depend on their structure as well as on the functionality (e.g., immunostimulatory or immunomodulatory) of the therapeutic. Preclinical studies are not yet capable of assessing the clinically relevant immunogenicity potential of these product-related factors. Simply addressing these risk factors as part of product development will not eliminate immunogenicity. Minimization of immunogenicity has to begin at the molecule design stage by reducing or eliminating antigenic epitopes and building in favorable physical and chemical properties.

Modulite technology in the development of formoterol HFA pMDI: clinical evidence and future opportunities

This article is based on published safety and efficacy data on formoterol pressurized metered-dose inhalers (pMDIs) developed with the Modulite technology. This technology allows the development of ozone-friendly inhaled drugs that replace the same doses of chlorofluorocarbon (CFC)-formulated products and enables the attainment of new formulations with extra-fine particles and improved lung deposition. Clinical pharmacology, as well as clinical studies against comparators, have demonstrated that formoterol Modulite and the existing dry powder inhaler and CFC formoterol formulations have a similar pharmacokinetic profile, are clinically equivalent in bronchodilating effects and exhibit a similar potential for systemic side effects. Therefore, the Modulite formoterol hydrofluoroalkane-based formulation in extra-fine particles is a valuable therapeutic option for both patients and physicians in the management of asthma and chronic obstructive pulmonary disease.

Inhaled insulin: overview of a novel route of insulin administration

Diabetes is a chronic disease characterized by inadequate insulin secretion with resulting hyperglycemia. Diabetes complications include both microvascular and macrovascular disease, both of which are affected by optimal diabetes control. Many individuals with diabetes rely on subcutaneous insulin administration by injection or continuous infusion to control glucose levels. Novel routes of insulin administration are an area of interest in the diabetes field, given that insulin injection therapy is burdensome for many patients. This review will discuss pulmonary delivery of insulin via inhalation. The safety of inhaled insulin as well as the efficacy in comparison to subcutaneous insulin in the various populations with diabetes are covered. In addition, the experience and pitfalls that face the development and marketing of inhaled insulin are discussed.

Efficacy and safety of AIR inhaled insulin compared to insulin lispro in patients with type 1 diabetes mellitus in a 6-month, randomized, noninferiority trial

BACKGROUND

Patients with type 1 diabetes may prefer features of AIR inhaled insulin (developed by Alkermes, Inc. [Cambridge, MA] and Eli Lilly and Company [Indianapolis, IN]; AIR is a registered trademark of Alkermes, Inc.) over insulin injection, but the two methods need to be compared for efficacy and safety.

METHODS

This multicenter, 6-month, parallel-group, noninferiority trial had 500 patients with type 1 diabetes randomized to morning doses of basal insulin glargine plus either preprandial injectable insulin lispro or preprandial AIR insulin. We hypothesized that AIR insulin is noninferior (upper bound of the 95% confidence interval < or = 0.4%) to insulin lispro for change-from-baseline hemoglobin A1C (A1C).

RESULTS

Baseline A1C was 7.95 +/- 0.08% for both groups. At end point, A1C was lower with insulin lispro than with AIR insulin by 0.27% (95% confidence interval 0.11, 0.43; P< 0.001). Noninferiority of AIR insulin to insulin lispro was not demonstrated, but similar percentages of patients in each group achieved A1C <7.0% (P = 0.448). Overall daily blood glucose was similar between groups at baseline (P = 0.879) and end point (P = 0.161). Two-hour postprandial blood glucose change from baseline was significantly (P < 0.001) higher with AIR insulin (20.77 +/- 4.33 mg/dL at 3 months and 15.85 +/- 3.08 mg/dL at end point) than with insulin lispro (3.29 +/- 4.14 mg/dL at 3 months and 1.67 +/- 2.91 mg/dL at end point). Overall hypoglycemia was similar between treatment groups (P = 0.355). The AIR insulin group had greater decrease in diffusing capacity of the lung for carbon monoxide at end point (P = 0.020) and greater incidence of cough (P = 0.024) and dyspnea (P = 0.030). Body weight decreased in the AIR insulin group and increased in the insulin lispro group.

CONCLUSIONS

Insulin lispro provided lower A1C than AIR insulin, but the difference may not be clinically relevant.

Two-year efficacy and safety of AIR inhaled insulin in patients with type 1 diabetes: An open-label randomized controlled trial

BACKGROUND

Patients with type 1 diabetes require intensive insulin therapy for optimal glycemic control. AIR((R)) inhaled insulin (system from Eli Lilly and Company, Indianapolis, IN) (AIR is a registered trademark of Alkermes, Inc., Cambridge, MA) may be an efficacious and safe alternative to subcutaneously injected (SC) mealtime insulin.

METHODS

This was a Phase 3, 2-year, randomized, open-label, active-comparator, parallel-group study in 385 patients with type 1 diabetes who were randomly assigned to receive AIR insulin or SC insulin (regular human insulin or insulin lispro) at mealtimes. Both groups received insulin glargine once daily. Efficacy measures included mean change in hemoglobin A1C (A1C) from baseline to end point, eight-point self-monitored blood glucose profiles, and insulin dosage. Safety assessments included hypoglycemic events, pulmonary function tests, adverse events, and insulin antibody levels.

RESULTS

In both treatment groups, only 20% of subjects reached the target of A1C <7.0%. A significant A1C difference of 0.44% was seen favoring SC insulin, with no difference between the groups in insulin doses or hypoglycemic events at end point. Patients in both treatment groups experienced progressive decreases in lung function, but larger (reversible) decrements in diffusing capacity of the lung for carbon monoxide (DL(CO)) were associated with AIR insulin treatment. Greater weight gain was seen with SC insulin treatment.

CONCLUSIONS

The AIR inhaled insulin program was terminated by the sponsor prior to availability of any Phase 3 data for reasons unrelated to safety or efficacy. Despite early termination, this trial provides evidence that AIR insulin was less efficacious in lowering A1C and was associated with a greater decrease in DL(CO) and increased incidence of cough than SC insulin in patients with type 1 diabetes.

Inhaled insulin is associated with prolonged enhancement of glucose disposal in muscle and liver in the canine

Diabetic patients treated with inhaled insulin exhibit reduced fasting plasma glucose levels. In dogs, insulin action in muscle is enhanced for as long as 3 h after insulin inhalation. This study was designed to determine whether this effect lasts for a prolonged duration such that it could explain the effect observed in diabetic patients. Human insulin was administered via inhalation (Exubera; n = 9) or infusion (Humulin R; n = 9) in dogs using an infusion algorithm that yielded matched plasma insulin kinetics between the two groups. Somatostatin was infused to prevent insulin secretion, and glucagon was infused to replace basal plasma levels of the hormone. Glucose was infused into the portal vein at 4 mg/kg/min and into a peripheral vein to maintain the arterial plasma glucose level at 160 mg/dl. Arterial and hepatic sinusoidal insulin and glucose levels were virtually identical in the two groups. Notwithstanding, glucose utilization was greater when insulin was administered by inhalation. At its peak, the peripheral glucose infusion rate was 4 mg/kg/min greater in the inhalation group, and a 50% difference between groups persisted over 8 h. Inhalation of insulin caused a greater increase in nonhepatic glucose uptake in the first 3 h after inhalation; thereafter, net hepatic glucose uptake was greater. Inhalation of insulin was associated with greater than expected (based on insulin levels) glucose disposal. This may explain the reduced fasting glucose concentrations observed in humans after administration of certain inhaled insulin formulations compared with subcutaneous insulin.

Safety and efficacy of inhaled insulin (AERx iDMS) compared with subcutaneous insulin therapy in patients with Type 1 diabetes: 1-year data from a randomized, parallel group trial

AIMS

Assessment of the long-term safety and efficacy of liquid inhaled insulin via AERx insulin Diabetes Management System (iDMS) in a basal/bolus treatment regimen of adults with Type 1 diabetes.

METHODS

Patients were randomized 2 : 1 to prandial inhaled (n = 205) or subcutaneous (s.c.) (n = 99) insulin, plus one/two daily injections of neutral protamine Hagedorn (NPH) insulin for 12 months. The primary endpoints were pulmonary function tests (PFT) and baseline changes in chest X-rays at 12 months. Safety and efficacy assessments were measured at regular intervals.

RESULTS

PFTs after 12 months were comparable between the groups, except for reduced per cent of predicted carbon monoxide lung diffusing capacity with inhaled insulin (difference: -2.03%, P = 0.04) occurring after the first 3 months and then stabilizing. There were no apparent treatment differences in chest X-rays. Overall risk of hypoglycaemia [risk ratio (RR) 1.02, P = 0.83] and adverse events were comparable between groups. Risk of nocturnal hypoglycaemia was higher in the inhaled group (RR 1.58, P = 0.001). Cough [10% (inhaled); 3% (s.c.)] tended to be mild in nature. Inhaled insulin was non-inferior to s.c. insulin for change in glycated haemoglobin (HbA(1c)) after 12 months [difference 0.18% (CI 95%-0.04; 0.39)]. At trial end, mean laboratory measured fasting plasma glucose was lower in the inhaled group (inhaled 9.2 mmol/l; s.c. 11.7 mmol/l; difference: -2.53 mmol/l, P < 0.001).

CONCLUSIONS

The safety and efficacy results in this trial were similar to those reported with other inhaled insulins; however, inhaled insulin using AERx iDMS requires further optimization to reduce nocturnal hypoglycaemia before it has comparable safety and efficacy to s.c. insulin aspart.

Time-action profile and patient assessment of inhaled insulin via the Exubera device in comparison with subcutaneously injected insulin aspart via the FlexPen device

BACKGROUND

The goal of our investigation was to compare the pharmacokinetics/pharmacodynamics properties of and patient preference for insulin aspart applied with the FlexPen (Novo Nordisk, Bagsvaerd, Denmark) (IAFP) with pulmonary human insulin applied with the Exubera (Pfizer, New York, NY) device (HIEX).

METHODS

Twelve patients with diabetes (six with type 1 and six with type 2; eight men, four women; age, 54.5 +/- 11.0 years; duration of diabetes, 16.5 +/- 10.6 years; hemoglobin A1c, 7.5 +/- 0.7%; body mass index, 29.5 +/- 7.2 kg/m(2); mean +/- SD) participated in an open-label, randomized, euglycemic clamp study. The patients received 11 units of IAFP or a dose-equivalent of (3 + 1 mg) insulin from HIEX in a randomized sequence on two different study days. Insulin plasma levels and the required glucose infusion rate (GIR) were monitored for a time period of 6 h. In addition, the patients' individual ratings from 1 (excellent) to 5 (poor) regarding several different handling items were assessed using a questionnaire.

RESULTS

No significant difference in the pharmacokinetics/pharmacodynamics parameters could be observed between IAFP and HIEX within the first 120 min. In the second part of the clamp procedure, plasma insulin levels (area under the curve versus time [AUC]) and the GIR was significantly higher after HIEX compared with IAFP (insulin AUC(120-360), 66,232 +/- 4,521 vs. 48,852 +/- 2,999 pmol/L, P < 0.05; GIR AUC(120-360), 8,928 +/- 1,334 vs. 6,805 +/- 1,655 mg/kg/min). A superior patient judgment was obtained for the FlexPen with regard to trust in insulin delivery (2.3 +/- 1.1 vs. 2.8 +/- 1.0), trust in correct insulin dosing (1.8 +/- 1.1 vs. 2.6 +/- 0.9), size (2.3 +/- 1.1 vs. 3.6 +/- 0.9), and appearance of the device (2.4 +/- 1.0 vs. 3.8 +/- 0.9) (P < 0.05, respectively).

CONCLUSIONS

Insulin treatment with HIEX was found to have pharmacokinetics/pharmacodynamics properties comparable to IAFP. Both insulin administration technologies were overall evaluated positive, but most patients preferred IAFP.

Current therapies and technological advances in aqueous aerosol drug delivery

Recent advances in aerosolization technology have led to renewed interest in pulmonary delivery of a variety of drugs. Pressurized metered dose inhalers (pMDIs) and dry powder inhalers (DPIs) have experienced success in recent years; however, many limitations are presented by formulation difficulties, inefficient delivery, and complex device designs. Simplification of the formulation process as well as adaptability of new devices has led many in the pharmaceutical industry to reconsider aerosolization in an aqueous carrier. In the acute care setting, breath-enhanced air-jet nebulizers are controlling and minimizing the amount of wasted medication, while producing a high percentage of respirable droplets. Vibrating mesh nebulizers offer advantages in higher respirable fractions (RFs) and slower velocity aerosols when compared with air-jet nebulizers. Vibrating mesh nebulizers incorporating formulation and patient adaptive components provide improvements to continuous nebulization technology by generating aerosol only when it is most likely to reach the deep lung. Novel innovations in generation of liquid aerosols are now being adapted for propellant-free pulmonary drug delivery to achieve unprecedented control over dose delivered and are leading the way for the adaptation of systemic drugs for delivery via the pulmonary route. Devices designed for the metered dose delivery of insulin, morphine, sildenafil, triptans, and various peptides are all currently under investigation for pulmonary delivery to treat nonrespiratory diseases. Although these devices are currently still in clinical testing (with the exception of the Respimat), metered dose liquid inhalers (MDLIs) have already shown superior outcomes to current pulmonary and systemic delivery methods.

The role of inhaled insulin in the treatment of type 2 diabetes

With the increasing prevalence of type 2 diabetes, it is imperative that health care providers adopt a more aggressive treatment approach to optimize glycemic control and to reduce the incidence of and costs associated with diabetes-related morbidity and mortality. Despite the well-recognized benefits of improved glycemic control in patients with type 2 diabetes, the majority of patients still have poor glycemic control. Diabetes is a progressive disease, and many patients who initially achieve glycemic control with oral therapy will eventually require the addition of insulin to maintain glycemic control. Subcutaneous injections, however, represent a barrier to patients' initiation of insulin therapy, and alternative methods of insulin delivery are likely to be viewed positively by patients and physicians. The recent approval of Exubera (Pfizer, New York, NY), a novel inhaled insulin delivery system for patients with type 1 or type 2 diabetes, may alleviate some of the barriers to the initiation of insulin. In studies in patients with type 2 diabetes, Exubera provided effective glycemic control that was comparable to that seen with subcutaneous insulin and superior to that seen with oral therapy, with a favorable safety and tolerability profile. Exubera can reduce the need for daily insulin injections and may become a useful alternative to existing treatments for the management of type 2 diabetes. Greater acceptance of new insulin delivery systems may lead to earlier introduction of insulin therapy, which should help more patients with diabetes achieve glycemic control sooner after diagnosis.

Recent challenges in insulin delivery systems: a review

Relatively, a large percentage of world population is affected by diabetes mellitus, out of which approximately 5-10% with type 1 diabetes while the remaining 90% with type 2. Insulin administration is essential for type 1 patients while it is required at later stage by the patients of type 2. Current insulin delivery systems are available as transdermal injections which may be considered as invasive. Several non-invasive approaches for insulin delivery are being pursued by pharmaceutical companies to reduce the pain, and hypoglycemic incidences associated with injections in order to improve patient compliance. While any new insulin delivery system requires health authorities' approval, to provide long term safety profile and insuring patients' acceptance. The inhalation delivery system Exubera((R)) has already become clinically available in the United States and Europe for patients with diabetes as non-invasive delivery system.

AIR inhaled insulin versus subcutaneous insulin: pharmacokinetics, glucodynamics, and pulmonary function in asthma

OBJECTIVE

This study evaluated pharmacokinetic and glucodynamic responses to AIR inhaled insulin relative to subcutaneous insulin lispro, safety, pulmonary function, and effects of salbutamol coadministration.

RESEARCH DESIGN AND METHODS

Healthy, mildly asthmatic, and moderately asthmatic subjects (n = 13/group, aged 19-58 years, nonsmoking, and nondiabetic) completed this phase I, open-label, randomized, crossover euglycemic clamp study. Subjects received 12 units equivalent AIR insulin or 12 units subcutaneous insulin lispro or salbutamol plus AIR insulin (moderate asthma group only) before the clamp.

RESULTS

AIR insulin exposure was reduced 34 and 41% (both P < 0.01) in asthmatic subjects (area under the curve(0-t'), 24.0 and 21.1 nmol x min x l(-1) in mild and moderate asthma subjects, respectively) compared with healthy subjects (35.2 nmol x min x l(-1)), respectively. Glucodynamic (G) effects were similar in healthy and mildly asthmatic subjects (G(tot) = 38.7 and 23.4 g, respectively; P = 0.16) and were reduced in moderately asthmatic subjects (G(tot) = 10.7 g). Salbutamol pretreatment (moderately asthmatic subjects) improved bioavailability. AIR insulin had no discernable effect on pulmonary function. AIR insulin adverse events (cough, headache, and dizziness) were mild to moderate in intensity and have been previously reported or are typical of studies involving glucose clamp procedures.

CONCLUSIONS

This study suggests that pulmonary disease severity and asthma treatment status influence the metabolic effect of AIR insulin in individuals with asthma but do not affect AIR insulin pulmonary safety or tolerability. In view of the potential interactions between diabetes treatment and pulmonary status, it is prudent to await the results of ongoing clinical trials in diabetic patients with comorbid lung disease before considering the use of inhaled insulin in such patients.

Current challenges in non-invasive insulin delivery systems: a comparative review

The quest to eliminate the needle from insulin delivery and to replace it with non- or less-invasive alternative routes has driven rigorous pharmaceutical research to replace the injectable forms of insulin. Recently, various approaches have been studied involving many strategies using various technologies that have shown success in delivering insulin, which are designed to overcome the inherent barriers for insulin uptake across the gastrointestinal tract, mucosal membranes and skin. This review examines some of the many attempts made to develop alternative, more convenient routes for insulin delivery to avoid existing long-term dependence on multiple subcutaneous injections and to improve the pharmacodynamic properties of insulin. In addition, this article concentrates on the successes in this new millennium in developing potential non-invasive technologies and devices, and on major new milestones in modern insulin delivery for the effective treatment of diabetes.

Inhaled insulin

Inhaled insulin has attractive pharmacodynamic properties with a fast onset of action which should lead to improved postprandial blood glucose concentrations. Comparisons with regular subcutaneous (sc) insulin in clinical studies, however, showed lower fasting blood glucose concentrations. Overall, clinical efficacy of inhaled insulin was comparable to that of regular sc insulin. Treatment with inhaled insulin was safe and well tolerated, with slight and reversible changes in lung function parameters and a rise in insulin antibodies (not associated with any clinical or safety parameters) as main adverse effects. Treatment satisfaction in open-label studies was higher with inhaled than with sc insulin, indicating that inhaled insulin might help to overcome one of the major hurdles of diabetes therapy, i.e. a timely initiation of insulin therapy. The first inhaled insulin formulation was approved in the US and Europe in January 2006, but some countries granted reimbursement only for selected patients, or did not reimburse treatment with inhaled insulin at all because of the high treatment costs. These are due to the rather low bioavailability of approximately 8-15%. Therefore, further research is needed to improve the bioavailability of inhaled insulin: e.g. through optimization of the inhaler, the insulin formulation, or the inhalation technique. In view of the potential for further improvement, inhaled insulin may become a very attractive alternative to sc insulin, in particular in patients in whom insulin therapy has to be initiated and/or intensified.

Inhaled insulin using AERx insulin Diabetes Management System (AERx iDMS)

Diabetes is a chronic, debilitating disease that afflicts millions of people worldwide and poor glycemic control in this disease leads to numerous microvascular and macrovascular complications. There is growing evidence that tight glycemic control prevents the development, and delays the progression, of microvascular complications and possibly macrovascular disease in patients with diabetes. All patients with Type 1 diabetes and many patients with Type 2 diabetes require intensive insulin therapy to achieve optimal glucose control. Although subcutaneous insulin therapy is the mainstay of insulin therapy, there are patients who fear needles and often refuse to start insulin therapy despite suboptimal glucose control. In these patients, inhaled insulin represents a non-invasive, painless method to administer intensive insulin treatment. The Novo Nordisk AS AERx iDMS (insulin Diabetes Management System) for inhaled insulin is a novel device that administers an aerosol of liquid insulin into the deep lung with dose adjustments as precise as one subcutaneous unit. Initial pharmacokinetic and pharmacodynamic studies demonstrate that the device delivers liquid insulin in a clear dose-response manner and with a rapid onset of action similar to the fast-acting analog insulins. At present, large, long-term Phase III studies are in progress to document not only the efficacy, but also the safety and feasibility of this device in the treatment of patients with diabetes.

Immunological responses to exogenous insulin

Regardless of purity and origin, therapeutic insulins continue to be immunogenic in humans. However, severe immunological complications occur rarely, and less severe events affect a small minority of patients. Insulin autoantibodies (IAAs) may be detectable in insulin-naive individuals who have a high likelihood of developing type 1 diabetes or in patients who have had viral disorders, have been treated with various drugs, or have autoimmune disorders or paraneoplastic syndromes. This suggests that under certain circumstances, immune tolerance to insulin can be overcome. Factors that can lead to more or less susceptibility to humoral responses to exogenous insulin include the recipient's immune response genes, age, the presence of sufficient circulating autologous insulin, and the site of insulin delivery. Little proof exists, however, that the development of insulin antibodies (IAs) to exogenous insulin therapy affects integrated glucose control, insulin dose requirements, and incidence of hypoglycemia, or contributes to beta-cell failure or to long-term complications of diabetes. Studies in which pregnant women with diabetes were monitored for glycemic control argue against a connection between IAs and fetal risk. Although studies have shown increased levels of immune complexes in patients with diabetic microangiopathic complications, these immune complexes often do not contain insulin or IAs, and insulin administration does not contribute to their formation. The majority of studies have shown no relationship between IAs and diabetic angiopathic complications, including nephropathy, retinopathy, and neuropathy. With the advent of novel insulin formulations and delivery systems, such as insulin pumps and inhaled insulin, examination of these issues is increasingly relevant.

Peptide Drug Delivery Strategies for the Treatment of Diabetes

Drug delivery strategies for diabetes have included a wide range of scientific and engineering approaches, including molecular design, formulation and device design. Molecular engineering has resulted in modified pharmacokinetics, such as rapid-acting or slow-release analogs of insulin. Long-acting insulin formulations are designed to meet the body's basal needs, whereas rapid-acting insulin formulations are designed to cover mealtime glucose spikes. Furthermore, the discovery of new therapeutic biomolecules, which like insulin need to be injected, will drive the need for more flexible and universally applicable delivery systems. Formulation design, such as particle engineering, can be used to modify pharmacokinetic profiles. In general, suspension formulations of insulin commonly demonstrate reduced solubility and result in sustained release. Similarly, depot injections can result in precipitation of insulin at the site of injection, again resulting in lower solubility and sustained release. Particle engineering also has been applied to pulmonary formulations for delivery to the deep lung. The creation of novel drug delivery methods for the treatment of diabetes should remove barriers to insulin therapy and increase patient acceptance and compliance. Eliminating routine injections with needle-free injectors, insulin pumps, inhalation, buccal sprays, intra-nasal delivery, and transdermal patches may offer increasingly attractive alternatives.

Delivering needle-free insulin using AERx iDMS (insulin diabetes management system) technology

BACKGROUND AND METHODS

Inhaled insulin has recently emerged as an alternative to subcutaneous insulin administration. One inhaled insulin device, AERx (a registered trademark of Aradigm Corp., Hayward, CA, or its affiliates in the United States and other countries) insulin diabetes management system (iDMS) (Novo Nordisk A/S, Bagsvaerd, Denmark), uses a unique liquid human insulin strip to deliver an aerosol of insulin to the lungs. AERx iDMS enables 1-unit increment dosing, and the device ensures that the insulin dose is released at the optimal point of inhalation for delivery to the lungs.

RESULTS

Compared with subcutaneous human insulin, the pharmacokinetic and pharmacodynamic profile of inhaled insulin with AERx iDMS is similar, but with a more rapid onset of action. Data from these pharmacokinetic studies have also demonstrated that inhaled insulin dosing with AERx iDMS is as consistent and reproducible as subcutaneous human insulin.

CONCLUSIONS

In individuals with diabetes, prandial inhaled insulin with AERx iDMS is as effective and well tolerated as subcutaneous prandial human insulin or insulin aspart in terms of glycemic control and overall hypoglycemia. No major safety concerns have been raised with respect to pulmonary function tests. Other clinical studies using AERx iDMS in special populations, such as smokers, people with asthma, or people suffering from upper respiratory tract infections, have provided important information regarding the use of inhaled insulin in these circumstances. Overall, pulmonary insulin delivery with the AERx iDMS device appears to be a promising safe and efficacious alternative to subcutaneous insulin injections.

Insulin antibodies with pulmonary delivery of insulin

BACKGROUND AND METHODS

Delivery of insulin to the deep lung presents unique challenges to the body's mucosal defense system. Pulmonary mucosal defense has the ability to discriminate between self and non-self antigens and has the potential for induction of immunologic tolerance. Published data concerning the immunogenicity of inhaled human insulin in drug trials will be reviewed, and data regarding the possible adverse effects of anti-insulin antibody development will be presented. Examination of the immunologic safety of inhaled human insulin will include discussion of comparator studies, factors affecting immunogenicity, the effects of insulin immunity on glycemic control and pulmonary function, and the relationship of insulin antibodies to dose requirements, pharmacodynamics, and hypoglycemia.

CONCLUSIONS

Inhaled human insulin, whether formulated as a powder or liquid, has been shown to be more immunogenic than comparator insulins given by subcutaneous routes; however, adverse effects of antibody formation have not been demonstrated.

Pulmonary function changes related to acute and chronic administration of inhaled insulin

The need for frequent insulin injections to achieve optimal glycemic control remains a major barrier to initiating and maintaining insulin therapy in diabetes. The inhaled route of insulin administration offers many potential advantages. However, there are ongoing concerns regarding the pulmonary safety of inhaled insulin. Published studies reporting pulmonary safety and data submitted to the Food and Drug Administration were reviewed. All studies were open-label, included adult subjects with type 1 and 2 diabetes, and excluded patients with underlying lung disease. Inhaled insulin was compared with subcutaneous insulin and oral agents. Inhaled insulin is associated with small, consistent reductions in lung function, primarily forced expiratory volume in 1 s (FEV(1)) and diffusion capacity for carbon monoxide (DL(CO)). The small reductions in lung function occurred early (within 12 weeks) and did not progress over time. The magnitudes of the reductions were 30-50 mL for FEV(1) and 0.5-1.0 standard units for DL(CO). Collectively, the data indicate that inhaled insulin is safe in studies with duration up to 4 years. The Food and Drug Administration requires monitoring of lung function on a regular basis.

Eficacia y seguridad de la insulina inhalada en el tratamiento de la diabetes mellitus

OBJECTIVE

To evaluate the efficacy and safety of inhaled insulin.

DESIGN

Systematic review.

DATA SOURCES

Reference data bases, MEDLINE (1999 to November 2005) and EMBASE (2000 to November 2005), the CENTRAL base (Cochrane Library), the European Drug Agency, the Food and Drug Administration, the International Network of Technology Evaluation Agencies, the European Network for Early Detection (EuroScan), and various research registers.

STUDIES

Eight clinical trials were recovered. Studies not comparing inhaled with subcutaneous insulin and those that did not measure metabolic control or satisfaction and quality of life were excluded.

DATA EXTRACTION

Critical reading using the methods proposed by the CASPe programme.

RESULTS

The difference between the 2 groups in mean values of descent of glycosylated haemoglobin was -0.07% (95% CI, -0.32 to 0.17) for type-2 diabetics; and between 0.16% (95% CI, -0.01 to 0.32) and -0.16% (95% CI, -0.34 to 0.01) in type-1 diabetics. Hypoglucaemias per subject-month were similar (between 0.83 and 1.57 in type-2 diabetics and between 8.6 and 9.9 in type-1 diabetics). Quality of life and satisfaction were favourable to the intervention group (P< .05). Secondary effects were comparable except in the appearance of cough (21%-27% in inhaled and 2%-7% in subcutaneous insulin).

CONCLUSIONS

Inhaled insulin is comparable to subcutaneous insulin in metabolic control, the number of hypoglucaemias and side-effects. However, the trials reviewed showed certain problems of internal and external validity. Studies with longer follow-up are needed, in order to evaluate possible lung disorders.

First approved inhaled insulin therapy for diabetes mellitus

The long-term benefits of tight glycemic control in preventing microvascular and macrovascular complications are well established in both Type 1 diabetes mellitus (Type 1 DM) and Type 2 diabetes mellitus (Type 2 DM). Nonetheless, achievement of recommended haemoglobin A1c (HbA(1c)) goals (< or = 6.5 - 7.0%) has remained elusive, especially in patients with diabetes who require insulin therapy. Delayed/suboptimal titration of insulin is partly related to poor acceptance of multiple injection regimen by both physicians and patients. EXUBERA (human insulin [rDNA origin]; Pfizer), the first approved inhaled insulin for the treatment of diabetic patients, has been shown to be safe and as effective as regular/rapidly acting insulin in improving glycemic control. In addition to controlling postprandial glucose excursions, EXUBERA exerts a major action to reduce fasting plasma glucose (FPG) concentration. Thus, it has the potential to be used as a monotherapy in Type 2 DM, as well as in combination with an insulin sensitizer in Type 2 DM or in combination with long-acting insulin in both Type 2 DM and Type 1 DM.

The impact of large tidal volume ventilation on the absorption of inhaled insulin in rabbits

Previous studies have shown that ventilation patterns affect absorption of inhaled compounds. Thus, the aim of this study was to investigate the effect of large tidal volume ventilation (LTVV) on the absorption of inhaled insulin in rabbits. Mechanically ventilated rabbits were given human insulin via a nebuliser system, and plasma insulin was measured for the following 120min. Ventilation was adjusted to (1) normal tidal volume ventilation (NTVV) for the entire period after dosing (NTVV group), to (2) LTVV for the entire period after dosing (LTVV group), to (3) NTVV except for 15min LTVV immediately after dosing (Early LTVV group), or to (4) NTVV except for 15min LTVV starting at 60min after dosing (late LTVV group). Insulin absorption (AUC(ins(0-120min))) was increased by 149% for the LTVV group compared to NTVV group (p<0.01) with increased maximal insulin concentration (106%, p=0.03). The Early LTVV group showed a changed absorption profile. For the late LTVV group an increase in insulin levels was observed after the LTVV period (not significant compared to the NTVV group). These data could potentially have implications for patients using inhaled insulin in situations where a change in breathing pattern is seen, such as exercise.

Alternatives routes of insulin delivery

Optimal glycaemic control is necessary to prevent diabetes-related complications. An intensive treatment, which could mimic physiological insulin secretion, would be the best one. However subcutaneous insulin treatment is not physiologic and represents a heavy burden for patients with type 1 and type 2 diabetes mellitus. Consequently, more acceptable, at least as effective, alternative routes of insulin delivery have been developed over the past years. Up to now, only pulmonary administration of insulin (inhaled insulin) has become a feasible alternative to cover mealtime insulin requirements and one of the various administration systems was recently approved for clinical use in Europe and the United States. But, due to advances in technology, other routes, such as transdermal or oral (buccal and intestinal) insulin administration, could become feasible in a near future, and they could be combined together to offer non-invasive, efficacious and more physiological way of insulin administration to patients with diabetes.

Inhalation of human insulin (exubera) augments the efficiency of muscle glucose uptake in vivo

This study assessed the site of increased glucose uptake resulting from insulin inhalation, quantified its effect under steady-state glucose concentrations, and identified the time to onset of effect. Human insulin was administered to 13 beagles via inhalation (Exubera [insulin human (rDNA origin)] Inhalation Powder; n = 7) or infusion into the inferior vena cava (Humulin R; n = 6) using an algorithm to match plasma insulin levels and kinetics for both groups. Somatostatin and glucagon were infused. Glucose was delivered into the portal vein (4 mg x kg(-1) x min(-1)) and a peripheral vein, as needed, to maintain arterial plasma glucose levels at 180 mg/dl. Hepatic exposure to insulin and glucose and liver glucose uptake were similar in both groups. Despite comparable arterial insulin and glucose levels, hind-limb glucose uptake increased 2.4-fold after inhalation compared with infusion due to increased muscle glucose uptake. Glucose infusion rate, nonhepatic glucose uptake, and tracer-determined glucose disposal were about twice as great compared with intravenous insulin. The effect appeared after 1 h, persisting at least as long as arterial insulin levels remained above basal. Pulmonary administration of insulin increases nonhepatic glucose uptake compared with infusion, and skeletal muscle is the likely site of that effect.

Inhaled insulin delivery--where are we now?

Since 1925, when the concept of treating diabetes with inhaled insulin (INH) was originally published, a number of clinical challenges have been resolved through technological advancements. Efforts by pharmaceutical partnerships or individual companies have resulted in the development of both injection-free devices and novel insulin formulations. Four different INH systems are now in phase 3 of clinical development, and several other INH systems are in earlier stages of clinical study. Clinical data consistently demonstrate that INH therapy is comparable to subcutaneous (SC) therapy in improving glycaemic control in patients with either type 1 or type 2 diabetes, generally without greater risk of overall hypoglycaemia. INH is generally well tolerated and appears to be safe. Adverse-event profiles for INH therapies are similar to SC insulin therapy, with the majority of events being reported as being mild to moderate. Long-term safety studies are ongoing, with emphasis on evaluating the impact of INH therapy on pulmonary function and immune responses. Although small, reversible decreases in pulmonary diffusion capacity (DL(co)) and FEV1 have been reported in response to INH, pulmonary function and structure do not appear to be affected in any clinically significant way. While insulin antibodies are increased in INH therapy, these antibodies have not been correlated with haemoglobin A1c (HbA1c), insulin dosage, hypoglycaemia, pulmonary function or adverse events. Nevertheless, properly controlled, long-term studies will best answer any remaining concerns. From the patient's perspective, INH therapy is preferred by the majority of patients over conventional SC insulin therapy. Studies have shown that patients prefer INH therapy, because it provides greater lifestyle flexibility and social acceptability while at the same time avoiding the pain associated with injection. Thus, after more than 80 years during which the injection route has been the only means of administering insulin, patients and physicians may soon avail themselves of another valuable tool in management of diabetes.