Dose response of inhaled dry-powder insulin and dose equivalence to subcutaneous insulin lispro

Bioequivalence and comparative pharmacodynamics of insulin lispro 200 U/mL relative to insulin lispro (Humalog®) 100 U/mL

Insulin lispro 200 U/mL (IL200) is a new strength formulation of insulin lispro (Humalog®, IL100), developed as an option for diabetic patients on higher daily mealtime insulin doses. This phase 1, open‐label, 2‐sequence, 4‐period crossover, randomized, 8‐hour euglycemic clamp study aimed to demonstrate the bioequivalence of IL200 and IL100 after subcutaneous administration of 20 U (U) to healthy subjects (n = 38). Pharmacokinetic (PK) and pharmacodynamic (PD) responses were similar in both formulations. All 90%CIs for the ratios of area under the concentration‐versus‐time curve from time zero to the time of the last measurable concentration (AUC_0–tlast) and maximum observed drug concentration (C_max), as well as the total glucose infused throughout the clamp (G_tot) and the maximum glucose infusion rate (R_max), were contained within 0.80 and 1.25. Time of maximum observed drug concentration (t_max) was similar between formulations, with a median difference of 15 minutes and a 95%CI of the difference that included zero. Inter‐ and intrasubject variability estimates were similar for both formulations. Both formulations were well tolerated. IL200 was bioequivalent to IL100 after subcutaneous administration of 20‐U single doses, and PD responses were comparable between formulation strengths.

Dry powders for oral inhalation free of lactose carrier particles

Dry powder inhaler (DPI) products have traditionally comprised a simple formulation of micronised drug mixed with a carrier excipient, typically lactose monohydrate. The presence of the carrier is aimed at overcoming issues of poor flowability and dispersibility, associated with the cohesive nature of small, micronised active pharmaceutical ingredient (API) particles. Both the powder blend and the DPI device must be carefully designed so as to ensure detachment of the micronised drug from the carrier excipient on inhalation. Over the last two decades there has been a significant body of research undertaken on the design of carrier-free formulations for DPI products. Many of these formulations are based on sophisticated particle engineering techniques; a common aim in formulation design of carrier-free products being to reduce the intrinsic cohesion of the particles, while maximising dispersion and delivery from the inhaler. In tandem with the development of alternative formulations has been the development of devices designed to ensure the efficient delivery and dispersion of carrier-free powder on inhalation. In this review we examine approaches to both the powder formulation and inhaler design for carrier-free DPI products.

Lipid-based carriers for pulmonary products: preclinical development and case studies in humans

A number of lipid-based technologies have been applied to pharmaceuticals to modify their drug release characteristics, and additionally, to improve the drug loading for poorly soluble drugs. These technologies, including solid-state lipid microparticles, many of which are porous in nature, liposomes, solid lipid nanoparticles and nanostructured lipid carriers, are increasingly being developed for inhalation applications. This article provides a review of the rationale for the use of these technologies in the pulmonary delivery of drugs, and summarizes the manufacturing processes and their limitations, the in vitro and in vivo performance of these systems, the safety of these lipid-based systems in the lung, and their promise for commercialization.

Confusion Regarding Duration of Insulin Action: A Potential Source for Major Insulin Dose Errors by Bolus Calculators

People with diabetes on insulin pumps often use a bolus calculator (BC) to obtain insulin dose recommendations. After the first bolus of the day, residual insulin activity, called bolus insulin on board (BOB), must be correctly accounted for to reduce the size of subsequent boluses and minimize the insulin stacking that would otherwise occur. Critical to achieving this calculation is having an appropriate duration of insulin action (DIA) setting in the BC. Unfortunately, the widespread use of inappropriately short DIAs may be causing unrecognized "stacking" of insulin that leads to unexplained hypoglycemic events. Currently, there is no widely accepted definition or value of the DIA for use in a BC. Various shortcomings regarding the selection of an appropriate DIA setting have led to considerable confusion among clinicians and insulin pump users about this important concept. Traditional pharmacological studies used to determine the pharmacodynamic (PD) properties of rapid-acting insulins create a misleading impression that insulin action times (IATs) in daily life vary from 3 to 5 hours and cause IATs to appear more variable than they actually are. These IAT time ranges are not appropriate for use as the DIA time value required to obtain an accurate bolus recommendation from a BC. We highlight the problems that arise when an inappropriately short DIA leads to excessive bolus recommendations, provide a research protocol to accurately measure DIA, and suggest appropriate DIA time recommendations for use in current clinical practice.

Standard and Novel Treatment Options for Metabolic Syndrome and Diabetes Mellitus

OPINION STATEMENT

Type II diabetes and metabolic syndrome are 2 intertwined conditions that are critical to the healthcare landscape in the United States and abroad. Patients with either diabetes or metabolic syndrome can have a dramatically increased risk of developing cardiovascular disease. Numerous treatment options have existed for some time, which include nonpharmacologic and pharmacologic therapies. In addition, within the last decade, a multiple of novel treatment options have emerged for the management of hyperglycemia in particular. By targeting novel pathways beyond the secretion and supply of insulin, these new therapeutics provide a valuable adjunct to the currently available therapies for diabetes and metabolic syndrome. Here we discuss the current guideline-driven usage of standard therapies with some novel indications. In addition, we discuss the novel therapies for the treatment of hyperglycemia, their mechanisms of action, and appropriate therapeutic indications.

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.

Ultrafast-acting insulins: state of the art

Optimal coverage of prandial insulin requirements remains an elusive goal. The invention of rapid-acting insulin analogs (RAIAs) was a big step forward in reducing postprandial glycemic excursions in patients with diabetes in comparison with using regular human insulin; however, even with these, the physiological situation cannot be adequately mimicked. Developing ultrafast-acting insulins (UFIs)-showing an even more rapid onset of action and a shorter duration of action after subcutaneous (SC) administration-is another step forward in achieving this goal. The need for UFIs has been gradually recognized over the years, and subsequently, a number of different approaches to cover this need are in clinical development. A rapid increase in circulating insulin levels can be achieved by different measures: modification of the primary structure of insulin molecule (as we know from RAIAs), addition of excipients that enhance the appearance in the monomeric state post-injection, or addition of enzymes that enable more free spreading of the insulin molecules in the SC tissue. Other measures to increase the insulin absorption rate increase the local blood flow nearby the insulin depot in the SC tissue, injecting the insulin intradermally or applying via another route, e.g., the lung. The development of these approaches is in different stages, from quite early stages to nearing market authorization. In time, daily practice will show if the introduction of UFIs will fulfill their clinical promise. In this review, the basic idea for UFIs will be presented and the different approaches will be briefly characterized.

Clinical performance of a device that applies local heat to the insulin infusion site: a crossover study

BACKGROUND

Fast-acting insulin analogs have been available since 1996. The absorption rate of these insulins is still too slow to mimic the physiological insulin action in healthy subjects. This study investigates the clinical performance of InsuPatch™, a local skin-heating device, on postprandial glucose excursion.

METHODS

Twenty-four type 1 diabetes mellitus subjects on continuous subcutaneous insulin infusion were included in this crossover study [10 male, 14 female, age: 43.5 ± 11.3 years, diabetes duration: 18.3 ± 10.5 years, glycosylated hemoglobin: 7.4 ± 0.8%, body mass index: 25.0 ± 3.0 kg/m(2) (mean ± standard deviation)]. The impact of local skin heating was measured by dividing the two-hour area under the curve by integration time (AUC/t(120)) for blood glucose (BG) above baseline after two standardized breakfast and dinner meal pairs (with and without heating) per subject. For the first breakfast pair, venous insulin concentration was also measured.

RESULTS

A significant reduction was found for the AUC/t(120) after breakfast and after dinner meals (42 breakfast meal pairs, AUC/t(120) not heated 66.4 ± 32.8 mg/dl vs heated 56.8 ± 34.0 mg/dl, p = .017; 38 dinner meal pairs, AUC/t(120) not heated 30.8 ± 31.0 mg/dl vs heated 18.4 ± 23.9 mg/dl, p = .0028). The maximum venous insulin concentration with heating was 27% higher than without heating (n = 23). The number of hypoglycemic events on days with heating (n = 9) was similar to the number of days without heating (n = 13).

CONCLUSIONS

Local heating of the skin around the infusion site significantly reduced postprandial BG by enhancing insulin absorption. The heating device was well tolerated, and it could facilitate development of closed-loop systems.

Guidelines for optimal bolus calculator settings in adults

Bolus insulin calculators (BCs) became available in insulin pumps in 2002 and are being integrated into glucose meters and portable device applets for use with multiple daily injections. A retrospective analysis of continuous subcutaneous insulin infusion data from the Actual Pump Practices (APP) study is used in this article to generate formulas for more precise BC settings. A well-designed BC determines accurate bolus doses for carbohydrate intake and for correcting elevated glucose levels. It should also provide the logic necessary to track residual bolus insulin and reduce bolus recommendations to minimize insulin stacking. To provide appropriate bolus doses, a BC requires accurate settings for the carbohydrate factor or insulin:carbohydrate ratio, glucose correction factor, duration of insulin action, and correction target. We provide guidelines to select BC settings from the user's current total daily dose (TDD) of insulin and to determine more appropriate BC settings from an improved TDD based on the mean glucose level.

Dose-dependent delay of the hypoglycemic effect of short-acting insulin analogs in obese subjects with type 2 diabetes: a pharmacokinetic and pharmacodynamic study

OBJECTIVE

Injected volume and subcutaneous adipose tissue blood flow (ATBF) affect insulin absorption. Pharmacokinetics of short-acting insulin analogs were established by assessing injection of small doses in lean subjects, healthy or with type 1 diabetes. In obese patients, however, daily dosages are larger and ATBF is decreased. This study assessed the kinetics of a short-acting insulin analog in obese subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Euglycemic clamps after subcutaneous lispro injections were performed. Six healthy control subjects received 10 units. Seven obese (BMI 38.3 ± 7.0 kg/m(2)) subjects with type 2 diabetes received 10, 30, and 50 units. Plasma lispro was measured by specific radioimmunoassay and ATBF by the (133)Xe-washout technique.

RESULTS

ATBF was 64% lower in subjects with type 2 diabetes than in control subjects. After 10 units injection, time to lispro plasma peak (T(max)) was similar (48.3 vs. 55.7 min; control subjects versus type 2 diabetic subjects), although maximal concentration (C(max))/dose was 41% lower in subjects with type 2 diabetes, with lower and delayed maximal glucose infusion rate (GIR(max): 9.0 vs. 0.6 mg/kg/min, P < 0.0001, 69 vs. 130 min, P < 0.0001, respectively). After 30- and 50-unit injections, T(max) (88.6 and 130.0 min, respectively) and time to GIR(max) (175 and 245 min) were further delayed and dose related (r(2) = 0.51, P = 0.0004 and r(2) = 0.76, P < 0.0001, respectively).

CONCLUSIONS

Absorption and hypoglycemic action of increasing dosages of lispro are critically delayed in obese subjects with type 2 diabetes.

A dry powder formulation of liposome-encapsulated recombinant secretory leukocyte protease inhibitor (rSLPI) for inhalation: preparation and characterisation

Inhaled recombinant secretory leukocyte protease inhibitor (rSLPI) has shown potential for the treatment of inflammatory lung conditions. Rapid inactivation of rSLPI by cathepsin L (Cat L) and rapid clearance from the lungs has limited clinical efficacy to date. Previous studies by us have shown that encapsulation of rSLPI within1,2-dioleoyl-sn-glycero-3-[phospho-L-serine]/cholesterol (DOPS/Chol) liposomes protects rSLPI against Cat L inactivation in vitro. Liquid DOPS-rSLPI preparations were found to be unstable upon long-term storage and nebulisation. The aim of this study was therefore to develop a method of manufacture for preparing DOPS-rSLPI liposomes as a dry powder for inhalation. DOPS-rSLPI dry powders were lyophilised and subsequently micronised with a novel micronisation aid. The effects of formulation and processing on rSLPI stability, activity, and uniformity of content within the powders were characterised. Using D-mannitol as the micronisation aid, dry powder particles in the inhalable size range (<5 μm) were prepared. By optimising process parameters, up to 54% of rSLPI was recovered after micronisation, of which there was no significant loss in anti-neutrophil elastase activity and no detectable evidence of protein degradation. Aerosolisation was achieved using a dry powder inhaler, and mass median aerodynamic diameter (MMAD) was evaluated after collection in a cascade impactor. Aerosolisation of the DOPS-rSLPI dry powder yielded 38% emitted dose, with 2.44 μm MMAD. When challenged with Cat L post-aerosolisation, DOPS-rSLPI dry powder was significantly better at retaining a protective function against Cat L-induced rSLPI inactivation compared to the aqueous DOPS-rSLPI liposome dispersion and was also more stable under storage.

How pharmacokinetic and pharmacodynamic principles pave the way for optimal basal insulin therapy in type 2 diabetes

This pedagogical review illustrates the differences between pharmacokinetic (PK) and pharmacodynamic (PD) measures, using insulin therapy as the primary example. The main conclusion is that PD parameters are of greater clinical significance for insulin therapy than PK parameters. The glucose-clamp technique, the optimal method for determining insulin PD, is explained so that the reader can understand the important studies in the literature. Key glucose-clamp studies that compare two basal insulin analogues - insulin glargine and insulin detemir - to Neutral Protamine Hagedorn insulin and to each other are then presented. The review further explains how PD parameters have been translated into useful clinical concepts and simple titration algorithms for everyday clinical practice. Finally, the necessity of overcoming patient and/or physician barriers to insulin therapy and providing continuing education and training is emphasised.

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.

Review of the mechanism of action and clinical efficacy of recombinant human hyaluronidase coadministration with current prandial insulin formulations

For patients with type 1 or type 2 diabetes, achieving good glycemic control is critical for successful treatment outcomes. As many patients remain unable to reach glycemic goals with currently available rapid-acting analog insulins, ultrafast insulin products are being developed that provide an even faster pharmacokinetic profile compared with current rapid prandial insulin products. The overall strategy of these ultrafast insulin products is to better mimic the normal physiologic response to insulin that occurs in healthy individuals to further improve glycemic control. Recombinant human hyaluronidase (rHuPH20) is a genetically engineered soluble hyaluronidase approved by the U.S. Food and Drug Administration as an adjuvant to increase the absorption and dispersion of other injected drugs; mammalian hyaluronidases as a class have over 6 decades of clinical use supporting the safety and/or efficacy of hyaluronidase coadministration. Clinical findings have demonstrated that coadministration of rHuPH20 with insulin or an insulin analog achieved faster systemic absorption, reduced inter- and intrapatient variability of insulin absorption, and achieved faster metabolic effects compared with injection of either insulin formulation alone. The magnitude of this acceleration is similar to the incrementally faster absorption of prandial insulin analogs as compared with regular insulin. In addition, coadministration of rHuPH20 with regular insulin or insulin analog also improved the achievement of prandial glycemic targets. Thus, rHuPH20 coadministration shows promise as a method of establishing a more rapid insulin profile to prandial insulin in patients with diabetes and has the potential to yield substantial improvements in postprandial glycemic excursion.

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.

AIR insulin capsules of different dose strengths may be combined to yield equivalent pharmacokinetics and glucodynamics

BACKGROUND

In order to assess pharmacokinetic (PK) and glucodynamic (GD) attributes relevant to the end user of an inhaled insulin, this study examined the exposure and GD effect of doses of AIR inhaled insulin (Eli Lilly and Co., Indianapolis, IN) (AIR is a registered trademark of Alkermes, Inc., Cambridge, MA) by combining capsules of different strengths in healthy subjects.

METHODS

Fifty-nine healthy, nonsmoking, male or female subjects with normal pulmonary function were enrolled in an open-label, randomized, crossover study. Subjects underwent up to five euglycemic glucose clamp procedures, separated by 5-18 days. The five AIR insulin treatments tested included one 6 unit-equivalent (U-eq) capsule containing 2.6 mg of insulin, three 2 U-eq (0.9 mg) capsules (2.7 mg total), one 10 U-eq (3.9 mg) capsule, one 6 U-eq capsule plus two 2 U-eq capsules (4.4 mg total), and two 10 U-eq capsules (7.8 mg total). Samples for PK and GD assessments were taken up to 10 h post-dose.

RESULTS

Based on both PK (area under the curve from time 0 to time of return to baseline and maximum concentration) and GD (total amount of glucose infused and maximum glucose infusion rate) responses, administration of a 6 U-eq capsule was equivalent to three 2 U-eq capsules; 90% confidence intervals for the ratios were contained within the interval (0.8, 1.25). Similarly, both overall exposure and glucodynamic response after administration of a 10 U-eq capsule were comparable to the 6 U-eq plus two 2 U-eq capsule combination. AIR insulin exhibited PK dose proportionality and dose-dependent increases in GD responses over the 2.6-7.8 mg dose range.

CONCLUSIONS

AIR insulin exhibited dose strength interchangeability and dose proportionality after single-dose administration in healthy subjects.

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.

Comparison of prandial AIR inhaled insulin alone to intensified insulin glargine alone and to AIR insulin plus intensified insulin glargine in patients with type 2 diabetes previously treated with once-daily insulin glargine

BACKGROUND

Patients with type 2 diabetes often initiate insulin with once-daily basal insulin. Over time, many patients intensify their insulin regimens in an attempt to attain and sustain glycemic targets. This study compares three intensification approaches: changing insulin glargine to preprandial AIR inhaled insulin (developed by Alkermes, Inc. [Cambridge, MA] and Eli Lilly and Company [Indianapolis, IN]; AIR is a registered trademark of Alkermes, Inc.), intensifying glargine via validated titration algorithms (IG), or adding AIR insulin while intensifying glargine (AIR + IG).

METHODS

Five hundred sixty patients with hemoglobin A(1c) (A1C) of 7.5-10.5%, on one or more antihyperglycemic medications, and on once-daily insulin glargine for > or =4 months were randomly allocated to one of the three treatments lasting 52 weeks. The primary objective assessed between-group differences in A1C mean change from baseline to 24 weeks using last-observation-carried-forward (LOCF) in the intent-to-treat population.

RESULTS

At 24 weeks, A1C was reduced from a mean baseline of 8.5% to 7.7%, 7.9%, and 7.5% for the AIR, IG, and AIR + IG groups, respectively. AIR produced 0.20% greater A1C decrease than IG (least-squares mean difference = -0.20%; 95% confidence interval [CI], -0.39, -0.02). AIR + IG had a 0.35% greater A1C decrease versus IG (95% CI, -0.57, -0.13). The -0.15% difference between AIR + IG versus AIR was not significant (P < 0.198). More hypoglycemia categorized as severe occurred with AIR alone versus IG alone at LOCF end points. More nocturnal hypoglycemia occurred with IG alone versus AIR alone and AIR + IG.

CONCLUSIONS

Preprandial inhaled insulin provides an alternative for patients not optimized on insulin glargine alone. Glycemic control, hypoglycemic risk, delivery preference, and regimen complexity must be considered when selecting insulin initiation and optimization regimens.

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.

Insulin structure and function

Throughout much of the last century insulin served a central role in the advancement of peptide chemistry, pharmacology, cell signaling and structural biology. These discoveries have provided a steadily improved quantity and quality of life for those afflicted with diabetes. The collective work serves as a foundation for the development of insulin analogs and mimetics capable of providing more tailored therapy. Advancements in patient care have been paced by breakthroughs in core technologies, such as semisynthesis, high performance chromatography, rDNA-biosynthesis and formulation sciences. How the structural and conformational dynamics of this endocrine hormone elicit its biological response remains a vigorous area of study. Numerous insulin analogs have served to coordinate structural biology and biochemical signaling to provide a first level understanding of insulin action. The introduction of broad chemical diversity to the study of insulin has been limited by the inefficiency in total chemical synthesis, and the inherent limitations in rDNA-biosynthesis and semisynthetic approaches. The goals of continued investigation remain the delivery of insulin therapy where glycemic control is more precise and hypoglycemic liability is minimized. Additional objectives for medicinal chemists are the identification of superagonists and insulins more suitable for non-injectable delivery. The historical advancements in the synthesis of insulin analogs by multiple methods is reviewed with the specific structural elements of critical importance being highlighted. The functional refinement of this hormone as directed to improved patient care with insulin analogs of more precise pharmacology is reported.

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.

AIR Inhaled Insulin System: a novel insulin-delivery system for patients with diabetes

Over time, most patients with Type 2 diabetes require insulin-replacement therapy to attain and sustain the increasingly stringent glycemic goals. Initiation of subcutaneous insulin may be delayed due to patient or provider resistance. This delay may increase the risk of complications from long-term hyperglycemia. The development of inhaled insulin-delivery systems has been pursued to facilitate earlier initiation and optimization of insulin therapy to achieve better treatment outcomes. The AIR((R)) Inhaled Insulin System utilizes relatively large, low-density particles, allowing efficient drug delivery to the deep lung from a simple inhaler. In clinical studies it has provided similar postprandial glycemic control compared with subcutaneously injected, short-acting insulin, and was preferred by more patients. The purpose of this article is to describe the AIR Inhaled Insulin System, provide an overview of other insulin-delivery systems and discuss future strategies for the 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.

Pharmaceutical particle engineering via spray drying

This review covers recent developments in the area of particle engineering via spray drying. The last decade has seen a shift from empirical formulation efforts to an engineering approach based on a better understanding of particle formation in the spray drying process. Microparticles with nanoscale substructures can now be designed and their functionality has contributed significantly to stability and efficacy of the particulate dosage form. The review provides concepts and a theoretical framework for particle design calculations. It reviews experimental research into parameters that influence particle formation. A classification based on dimensionless numbers is presented that can be used to estimate how excipient properties in combination with process parameters influence the morphology of the engineered particles. A wide range of pharmaceutical application examples—low density particles, composite particles, microencapsulation, and glass stabilization—is discussed, with specific emphasis on the underlying particle formation mechanisms and design concepts.

Effects of smoking cessation, acute re-exposure and nicotine replacement in smokers on AIR inhaled insulin pharmacokinetics and glucodynamics

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* Only one other study (Becker et al.) has reported on the influence of smoking cessation and smoking resumption on inhaled insulin pharmacokinetics and glucodynamics, concluding that the rapid changes associated with smoking resumption carry the risk for hypoglycaemia and thus should not be used by active smokers.

WHAT THIS STUDY ADDS

* This is the first euglycaemic clamp study on the impact of smoking cessation, acute smoking re-exposure and nicotine replacement on AIR((R)) inhaled insulin pharmacokinetics and glucodynamics. * We demonstrate clinically and statistically significant shifts in glucodynamic response to acute re-exposure to a single cigarette, leading us to conclude that active smokers should be advised against inhaled insulin therapy until smoking abstinence is stable. * Additionally, these results are also the first to demonstrate an apparent independent effect of nicotine replacement therapy on insulin exposure and glucodynamic response.

AIMS

To explore the effects of smoking cessation and acute smoking re-exposure on the pharmacokinetic (PK) and glucodynamic (GD) profiles of AIR inhaled insulin (AIR Insulin) with or without nicotine replacement therapy (NRT).

METHODS

Nondiabetic smokers (n = 24) with normal pulmonary function completed a two-phase (four-period), open-label, randomized euglycaemic clamp study. During the initial study phase, subjects underwent glucose clamps following AIR Insulin dosing, shortly after smoking, 8-12 h after smoking, or following subcutaneous insulin lispro shortly after smoking. AIR Insulin PK and GD were again assessed during and after a 4-week smoking-cessation period with or without NRT. In the last study period, subjects smoked one cigarette shortly before final AIR Insulin dosing and glucose clamp, to study the effect of acute smoking re-exposure on inhaled insulin PK and GD.

RESULTS

Compared with the preceding active smoking phase, the administration of AIR Insulin in nondiabetic subjects undergoing a 4-week period of smoking abstinence resulted in a decrease in PK and GD of approximately 25% (P = 0.008 for both), an effect which was greater in subjects using NRT. Following rechallenge with a single cigarette (without NRT), GD response to AIR Insulin increased significantly (P = 0.006) towards precessation levels, relative to smoking abstinence. In subjects using NRT, however, the increase in GD was less pronounced.

CONCLUSION

Smoking, smoking cessation and acute re-exposure with a single cigarette are associated with clinically significant alterations in AIR Insulin pharmacokinetics and glucodynamics. AIR Insulin should not be used by smokers or those at risk for recidivism.

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.

Effect of upper respiratory tract infection on AIR inhaled insulin pharmacokinetics and glucodynamics in healthy subjects

The suitability of employing AIR Inhaled Insulin (AIR Insulin; AIR is a registered trademark of Alkermes) during acute upper respiratory tract infection (URI) has not been determined. Twenty-one healthy, non-diabetic subjects were enrolled in a single-sequence, two-period, euglycemic clamp study. Subjects received a single 12 U-equivalent dose of AIR Insulin before rhinovirus (RV16) inoculation and during symptomatic infection. Spirometry was used to evaluate pulmonary safety. AIR Insulin exposure (the area under the immunoreactive insulin (IRI) concentration vs time curve from time zero until the IRI concentrations returned to the predose baseline value (AUC(0-t'))) and glucodynamic response (total amount of glucose infused (G(tot))) were comparable before and during RV infection (AUC(0-t') 46,300 vs 52,600 pmol min/l, P=0.21; G(tot) 61,800 vs 68,700 mg, P=0.42, respectively). Variability of pharmacokinetic and pharmacodynamic parameters did not change during URI; either did the number or intensity of adverse events. No significant change in forced expiratory volume or forced vital capacity was observed following AIR Insulin administration or during URI. The AIR Insulin system provides similar pharmacokinetic and glucodynamic responses under conditions of an experimentally induced RV infection and is regarded as suitable for use in diabetic patients during URIs.

AIR inhaled insulin in subjects with chronic obstructive pulmonary disease: pharmacokinetics, glucodynamics, safety, and tolerability

OBJECTIVE

In this open-label, randomized, crossover study, pharmacokinetic and glucodynamic responses were compared in healthy subjects versus subjects with moderate chronic obstructive pulmonary disease (COPD), following administration of 12 units equivalent AIR inhaled insulin versus 12 units subcutaneous insulin lispro.

RESEARCH DESIGN AND METHODS

Three nonsmoking groups (n = 15 each)--healthy subjects (baseline mean +/- SD age 38 +/- 13 years, forced expiratory volume in 1 s [FEV1] 4.06 +/- 1.04 l), subjects with chronic bronchitis (aged 53 +/- 9 years, FEV1 2.14 +/- 0.60 l), and subjects with pulmonary emphysema (aged 58 +/- 6 years, FEV1 1.67 +/- 0.61 l)--were randomly assigned to one of three treatment sequences. Three euglycemic glucose clamp procedures were performed.

RESULTS

In subjects with chronic bronchitis and emphysema, AIR inhaled insulin administration resulted in reduced insulin exposure (area under the serum insulin concentration curve from time zero until time of return to baseline [AUC(0-t')]) (55.7%, P = 0.13 and 78.5%, P < 0.001, respectively) and reduced total insulin effect (total glucose infusion rate) (60.4%, P < 0.01 and 67.1%, P < 0.01, respectively) relative to healthy subjects. Subcutaneous insulin lispro administration resulted in similar responses across study groups for insulin exposure and metabolic effect. Intrasubject pharmacokinetic and glucodynamic variability ranged from 17 to 52% across groups. No significant differences were shown for pre- and postclamp pulmonary function tests. During clamps, FEV1 and forced vital capacity declined modestly in both COPD groups, with no difference between AIR insulin and subcutaneous insulin lispro.

CONCLUSIONS

Short-term exposure to AIR inhaled insulin was well tolerated by COPD subjects, showing similar time-exposure and time-action profiles, but with reduced insulin absorption and metabolic effect compared with healthy subjects. Further clinical evaluation is warranted in patients with comorbid diabetes and COPD.

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.

Inhaled insulin in patients with asthma and chronic obstructive pulmonary disease

The effect of inhaled insulin in subjects with diabetes and chronic lung disease, such as asthma or chronic obstructive pulmonary disease (COPD), is of particular interest because these diseases are quite common, and it is likely that patients with asthma or COPD who are poorly controlled on oral agents and are reluctant to start subcutaneous insulin would benefit from inhaled insulin to improve their glucose control. Since patients with asthma or COPD have varied pulmonary symptoms and abnormal pulmonary function, it is important to establish the pulmonary safety and efficacy of inhaled insulin in subjects with diabetes and asthma or COPD. Pharmacokinetic and pharmacodynamic studies in non-diabetic subjects with asthma consistently show lower absorption of inhaled insulin and lesser glucose lowering effects by approximately 30-40%, as compared to subjects without asthma. Thus, it would be expected that the dose of insulin required to obtain equivalent glycemic control would be higher by approximately 30-40% in subjects with asthma and diabetes (as compared to subjects without asthma but with diabetes). However, prior administration of a bronchodilator inhaler in individuals with asthma and diabetes reverses airway obstruction and thus may obviate the need for increased insulin requirements. In contrast to patients with asthma, in patients with COPD and diabetes, the absorption of inhaled insulin appears to be variable (higher or lower than in non-COPD subjects). Whether this variability is secondary to differences in inhalation devices or different study populations is not clear at present. Overall, data from the clinical studies indicate that inhaled insulin is effective and well tolerated in subjects with diabetes and chronic lung disease. However, preliminary, limited data from the longer-term clinical studies suggest that there is a marginally greater decline in pulmonary function tests in subjects with asthma/COPD and diabetes compared to subjects with diabetes and no chronic lung disease. Thus, there is a clear need for longer-term studies in subjects with diabetes and chronic lung disease in order to further clarify the safety and efficacy of inhaled insulin in this population.

The AIR inhaled insulin system: system components and pharmacokinetic/glucodynamic data

The diabetes epidemic and lack of adequate glycemic control in patients with diabetes emphasize the need for alternative diabetes treatment strategies. Although many new compounds have been developed, insulin remains the most potent agent for controlling glycemia. Inhaled insulin systems have been developed to alleviate the fear of insulin injections and to improve the convenience of insulin administration. The AIR Inhaled Insulin System being developed by Eli Lilly (Indianapolis, IN) and Alkermes (Cambridge, MA) uses AIR particle technology to deliver dry powder insulin to the deep lung. Pharmacokinetic and glucodynamic data in Phase 1 clinical trials have demonstrated that AIR Insulin is rapidly absorbed with prolonged insulin exposure and action compared to insulin lispro. AIR Insulin has also been shown to have dose equivalence and dose reproducibility across a range of doses, and it has been shown that three inhalations of the 2 U-equivalent dose can be interchanged with one 6 U-equivalent dose. A Phase 2 study demonstrated preference for AIR Insulin over subcutaneous injectable insulins, and a recent study reported that the system is easy to teach and use. Several Phase 3 studies are currently underway to further investigate the safety and efficacy and to evaluate the system's intention to meet provider and patient expectations.

Design of fine particles for pulmonary drug delivery

Particle design for inhalation is characterized by advances in particle processing methods and the utilization of new excipients. Processing methods such as spray drying allow control over critical particle design features, such as particle size and distribution, surface energy, surface rugosity, particle density, surface area, porosity and microviscosity. Control of these features has enabled new classes of therapeutics to be delivered by inhalation. These include therapeutics that have a narrow therapeutic index, require a high delivered dose, and/or elicit their action systemically. Engineered particles are also being utilized for immune modulation, with exciting advances being made in the delivery of antibodies and inhaled vaccines. Continued advances are expected to result in 'smart' therapeutics capable of active targeting and intracellular trafficking.

Inhaled insulins

As a result of knowledge gained from the management of asthma with inhalers and nebulisers, pulmonary delivery devices for insulin have been developed. Particle size of the aerosol particularly influences drug delivery. Although several pharmaceutical companies are developing different systems, Pfizer have launched the first inhaled insulin (Exubera). Clinical trials have taken place in patients with both type 1 and type 2 diabetes, but have shown similar glucose control as subcutaneous insulin delivery. However, patient satisfaction does seem to be increased in patients taking inhaled insulins. Further studies are needed to investigate compliance, side-effect profiles, quality of life, long-term glycaemia control and cost effectiveness.

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.

Effect of standard (self-directed) training versus intensive training for Lilly/Alkermes human insulin inhalation powder delivery system on patient-reported outcomes and patient evaluation of the system

BACKGROUND

Inhaled insulin may provide patients with diabetes a safe, efficacious method of insulin delivery without the burden of injection, but complexity of and time required for training in proper use of delivery systems have not been evaluated.

METHODS

This 4-week, multicenter, single-blind, randomized parallel-group study compared the effect of self-directed [written text-graphic directions for use (DFU) with patient-assistance phone number] or intensive (same DFU, personal training by study personnel, inspiratory flow rate coaching) training for the Lilly/Alkermes human insulin inhalation powder (HIIP) delivery system on patient-reported outcomes (PROs). Patients with type 2 diabetes poorly controlled on oral therapy (n = 102, mean hemoglobin A1C = 9.3%) were administered measures of vitality, diabetes-associated symptoms, fear of hypoglycemia, insulin-delivery system satisfaction, and a delivery system-specific evaluation questionnaire. Analysis of covariance models were used to compare the effect on PROs of treatment of diabetes for 1 month following the two training methods. Paired t tests were used to determine change in PROs after treatment with HIIP.

RESULTS

PROs did not differ significantly between training groups. Patients in both groups positively evaluated the delivery system, but the intensive group agreed significantly (P < 0.05) more strongly that the DFU was easy to follow. Improvements in vitality and symptoms of fatigue and increases in fear of hypoglycemia were detected among all patients after using HIIP (P < 0.05).

CONCLUSION

Training for this HIIP delivery system can be self-directed without detrimental effects on PROs, making it potentially a more patient-friendly insulin-delivery method that should appeal to both clinicians and patients.

Use of insulin immunoassays in clinical studies involving rapid-acting insulin analogues: Bi-insulin IRMA preliminary assessment

BACKGROUND

In clinical studies involving rapid-acting analogues (RAAs), insulin immunoreactivity is frequently measured, including endogenous, regular insulin (RI) and RAA immunoreactivities. Such a procedure implies equivalent cross-reactivities of all insulins present in serum. Commercially available human insulin immunoassays have been widely used, but their limitations (including hemolysis and anti-insulin antibodies) were not fully investigated. The aims of our study were to compare cross-reactivities of RI and RAAs in buffer and in serum and to investigate insulin immunoassay pitfalls.

METHODS

Cross-reactivities were assessed using Bi-insulin IRMA (Schering Cis-Bio International) in phosphate-buffered saline (PBS)-1% bovine serum albumin (BSA) and in pools of sera spiked with RI and RAAs (lispro and aspart). To investigate the influence of hemolysis, a pool of sera spiked with RAA was mixed with a concentrated hemolysate (final hemoglobin concentration 10 g/L) and incubated for 3 h at room temperature. To determine interference by anti-insulin antibodies, insulin was removed using charcoal from 18 sera with anti-insulin antibodies and from 17 sera without detectable anti-insulin antibodies. These insulin-free samples were then spiked with RI and RAAs and the immunoreactivity was determined.

RESULTS

Compared with buffer, cross-reactivity in serum for RI, lispro and aspart was lower (35%, 29% and 26% lower, respectively). Hemolysis degraded almost all RI and RAAs contained in the serum (>or=95%). Anti-insulin antibody interference was significant for RI and RAAs (p<or=0.004) and correlated with anti-insulin antibody level in the serum (p<or=0.001).

CONCLUSIONS

In serum, RI and RAA cross-reactivities are slightly lower than in buffer. For RAA assessment, hemolysed samples should be discarded and anti-insulin antibodies should be removed from samples before immunoreactivity measurements.

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.

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.

Non-invasive routes for insulin administration: current state and perspectives

Diabetes mellitus is a chronic disease that usually requires multiple insulin injections to achieve adequate glycaemic control. This represents a major cause of reduced compliance to treatment. Consequently, other routes for insulin administration have been explored. During recent years, much progress in the development of inhaled insulin has been made. Inhaled insulin has shown favourable properties, such as a rapid onset of action, improved bioavailability and good tolerability; thereby providing satisfaction and ease of administration. However, long-term safety of inhaled insulin needs to be assessed, and the cost would be higher than injectable insulin. Nasal, oral and transdermal insulins are undergoing early phases of pharmacological development. The purpose of this review is to describe the latest developments in the area of non-invasive routes for insulin delivery.

Diabetes therapy trials with inhaled insulin

Administration of insulin by inhalation was first attempted > 50 years ago. At that time, little was known concerning effective delivery systems and insulin formulations. The recent development of pulmonary delivery systems for the administration of insulin is driven by the reluctance of patients and their providers to initiate insulin earlier in the course of Type 2 diabetes, the desire to reduce the number of daily insulin injections for both Type 1 and 2 patients, and the recent emphasis on intensified glycaemic control including postprandial glycaemic control. The deep lung is a unique mucosal tissue having a surface area of > 100 m2 and is readily accessible both to the external environment and to drug delivery, provided that appropriate conditions are met. There have been four mid- to late-phase pulmonary insulin programmes using modern inhalation devices that will be reported in this paper. The programmes differ in the choice of delivery systems, the formulations of insulin and reported bioavailability, pharmacokinetic and glucodynamic profiles and adverse events. However, all systems successfully deliver insulin to the deep lung and biological effectiveness compares favourably with injected subcutaneous insulins.

Role of inhaled human insulin in the management of Type 1 and 2 diabetes

Inhaled human insulin (Exubera^®) has been approved by the FDA and other regulatory bodies for treatment in Type 1 and 2 diabetes in the USA. It is the first alternative to injectable insulin since the discovery of the insulin compound to treat diabetes. This article will review results of recent clinical studies that support the therapeutic efficacy and safety of inhalable insulin for use in patients with diabetes. The pharmacological profile of inhaled insulin with particular reference to inhaled human insulin and the potential to influence diabetes care is also discussed.