Prandial insulin: is inhaled enough?

Making Insulin Accessible: Does Inhaled Insulin Fill an Unmet Need?

Glycemic control is fundamental to the management of diabetes. However, studies suggest that a significant proportion of people with diabetes, particularly those using insulin, are not achieving glycemic targets. The reasons for this are likely to be multifactorial. The real and perceived risk of hypoglycemia and the need for multiple daily injections are widely recognized as key barriers to effective insulin therapy. Therefore, there is a clear unmet need for a treatment option which can help mitigate these barriers. Alternative methods of insulin administration have been under investigation for several years, and pulmonary delivery has shown the most promise to date. Inhaled Technosphere(®) Insulin (TI; Afrezza(®); MannKind Corporation) was approved in 2014 for use as prandial insulin in people with diabetes. TI shows a more rapid onset of action and a significantly faster decline in activity than current subcutaneous rapid-acting insulin analogs (RAAs), and TI is more synchronized to the physiologic timing of the postprandial glucose excursion. This results in lower postprandial hypoglycemia with similar glycemic control compared with RAAs, and less weight gain. Together with the ease of use of the TI inhaler and the reduction in the number of daily injections, these findings imply that TI may be useful in helping to overcome patient resistance to insulin, improve adherence and mitigate clinical inertia in health-care providers, with potential beneficial effects on glycemic control.

FUNDING

Writing and editorial support in the preparation of this publication was funded by Sanofi US, Inc., Bridgewater, New Jersey, USA. Funding for the article processing charges for this publication was provided by MannKind Corporation.

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.

Inhaled insulin: a breath of fresh air? A review of inhaled insulin

PURPOSE

Despite many advances in diabetes care over the last century, some elements of insulin therapy remain inadequate for optimal care of the patient with diabetes. There is a need for improved pharmacokinetics and pharmacodynamics of rapid-acting insulin analogues to mimic physiologic insulin secretion. In addition, a major barrier to successful insulin therapy has been patient resistance. Alternative routes of insulin administration, including inhaled insulin, have been under investigation for several years. This review discusses the rationale for pulmonary delivery of insulin, compares previous inhaled insulin products, reviews the literature on the safety and efficacy of a current inhaled insulin formulation under investigation, and compares this product with other prandial insulin products.

METHODS

English-language studies and reviews of inhaled insulin were searched in MEDLINE, the ClinicalTrials.gov registry (through May 2014), and the US Food and Drug Administration Website.

FINDINGS

Inhaled insulin has several favorable characteristics due to pulmonary anatomy/physiology and the lack of injections. Pharmacokinetic and pharmacodynamic studies have shown a time-action profile suitable for prandial insulin use. Inhaled insulin seems to be safe and effective compared with other prandial insulin products and may be preferable to subcutaneous rapid-acting insulin analogues in terms of time-action profiles and rates of hypoglycemia. Small decreases in forced expiratory volume in 1 second (FEV1) have been shown with inhaled insulin, although this finding is not progressive over time and reverses with cessation of the medication.

IMPLICATIONS

Although several inhaled insulin products have been under investigation, only one (Exubera(®) [Nektar Therapeutics, San Carlos, California/Pfizer Inc, New York, New York]) was approved by the US Food and Drug Administration, and it was pulled from the market after only a short period of time. Technosphere(®) insulin (MannKind Corporation, Valencia, California) is currently the only inhaled insulin that remains under investigation. A review of the past and present literature on inhaled insulin is pertinent in understanding the current status of inhaled insulin and its risks and benefits. The current literature suggests that inhaled insulin could be a valuable option for prandial insulin administration, with a favorable risk to benefit ratio in some patients.

Comparative pharmacoscintigraphic and pharmacokinetic evaluation of two new formulations of inhaled insulin in type 1 diabetic patients

In this open, single-dose study, we compared the lung deposition and bioavailability of two newly developed insulin formulations for pulmonary delivery. Twelve type 1 diabetic patients were administered the two insulin products (2 U/kg b.w.), which had been radiolabelled with (99m)Tc. The formulations were either microparticles of insulin without excipients (F1) or lipid-coated insulin microparticles (F2). Lung deposition was assessed by γ-scintigraphy imaging performed immediately after administration. Bioavailability was evaluated by quantifying serum insulin levels over a period of 6 h. Lung deposition was found to be 50 ± 9% and 24 ± 8% for the F1 and F2 formulations, respectively. The insulin AUC₀₋₃₆₀ ratio of F1/F2 was 188%, which was consistent with scintigraphic imaging. The concordance between imaging and biological results suggests that the lower bioavailability of F2 is due to its lower lung deposition and not to a reduced absorption into the blood stream. Additional in vitro experiments indicated that the lower performance of F2 was most probably related to a lower disaggregation efficiency of the powder when administered at a sub-optimal flow rate. The two formulations showed interesting pharmacokinetic profiles (T(max) of 26 and 16 min for F1 and F2, respectively) that mimic the physiological insulin secretion pattern. The bioavailability of the developed formulations was within the range of other DPI insulin formulations that have reached the final stages of clinical development.

Pharmacokinetic characterization of the novel pulmonary delivery excipient fumaryl diketopiperazine

BACKGROUND

Technosphere® [Bis-3,6(4-fumarylaminobutyl)-2,5-diketopiperazine (FDKP)] microparticles, the integral component of the Technosphere inhalation system, deliver drugs to the deep lung and have been used to administer insulin and glucagon-like peptide-1 via inhalation in clinical studies. Three studies were conducted to characterize FDKP pharmacokinetics, including assessments in subjects with diabetic nephropathy (DNP), in subjects with chronic liver disease (CLD), and in healthy subjects.

METHODS

An open-label, nonrandomized, two-period, fixed-sequence crossover absorption, distribution, metabolism, and excretion (ADME) study was conducted in six healthy nonsmoking men who received single intravenous and oral doses of [(14)C]FDKP solution, with serial sampling of blood, urine, feces, and expired air. Additionally, two single-dose, open-label, parallel-design studies with 20 mg of inhaled FDKP were conducted in (1) 12 diabetic subjects with normal renal function and 24 DNP subjects and (2) 12 healthy subjects and 21 CLD subjects.

RESULTS

In the ADME study, >95% of the intravenous dose and <3% of the oral dose were recovered in urine, with no evidence of metabolism. No significant pharmacokinetic differences were observed between healthy subjects and CLD subjects [geometric mean (% coefficient of variation) area under the curve from time 0 to 480 minutes (AUC(0-480)): 26,710 (34.8) and 31,477 (28.8) ng/ml·min, respectively]. Maximum observed drug concentration (C(max)) and AUC(0-480) were higher in DNP subjects than in subjects with normal renal function [C(max): 159.9 (59.4) ng/ml versus 147.0 (44.3) ng/ml; AUC(0-480): 36,869 (47.2) ng/ml·min versus 30,474 (31.8) ng/ml·min]. None of the differences observed were considered clinically significant.

CONCLUSIONS

Fumaryl diketopiperazine is predominantly cleared unchanged by the kidney with essentially no oral bioavailability. Technosphere is a safe delivery vehicle for medications administered via inhalation.

Evaluation of novel particles as an inhalation system for GLP-1

AIM

The feasibility of administering native glucagon-like peptide 1 (GLP-1) as GLP-1 Technosphere Inhalation Powder for diabetes therapy has been demonstrated in a rat model.

METHODS

GLP-1 Technosphere Inhalation Powders containing 5, 10 and 15% GLP-1 were prepared and administered to healthy female Sprague-Dawley rats and to male Zucker diabetic obese rats. Rats received a single dose of GLP-1 Technosphere Powder by pulmonary insufflation. GLP-1 pharmacokinetic and pharmacodynamic responses were measured.

RESULTS

Maximum circulating GLP-1 concentrations were achieved at approximately 10 min after dosing with detectable levels at 40 min. In a food consumption study, Sprague-Dawley rats receiving GLP-1 Technosphere Powder once-daily consumed less food than control rats for up to 24 h after dosing. Cumulative food consumption was decreased approximately 10% after 78 h. In an intraperitoneal glucose tolerance test, Zucker diabetic fatty rats receiving 2 mg GLP-1 Technosphere Powder (0.3 mg GLP-1) by pulmonary insufflation exhibited lower glucose concentrations and higher insulin concentrations than control rats. Pancreatic evaluations showed no differences in apoptotic index or cell proliferation of beta-cells. In addition, a dose-related increase in insulin expression within the pancreas was observed.

CONCLUSIONS

These data demonstrate the feasibility of administering native GLP-1 as GLP-1 Technosphere Inhalation Powder for diabetes therapy.