This study was a single-centre (Department of Internal Medicine, Division of Endocrinology and Metabolism, Medical University of Graz, Austria), randomised, multiple-dose, double-blind, two-period, crossover trial conducted in subjects with type 1 diabetes (Clinical trials.gov number: NCT00964418). Before initiation, the trial was reviewed and approved by the local independent ethics committee according to local regulations. The trial was performed in accordance with the Declaration of Helsinki and its amendments in force at the initiation of the trial. Subjects were informed of the risks and benefits of the trial and that they could withdraw at any time for any reason. Consent was obtained in writing before any trial-related activities, and the investigator retained the consent forms.
Study participants were men and women aged 18–35 years inclusive (younger adult group) or aged ≥65 years (elderly group) with type 1 diabetes for ≥12 months, and a fasting C-peptide level below 0.3 nmol/L. Other key inclusion criteria for the trial included subjects who had been treated with multiple daily insulin injections (or continuous SC insulin infusion) for ≥12 months; a body mass index (BMI) of 18.0–28.0 kg/m2 inclusive; a daily basal insulin requirement of ≥0.2 IU/kg/day; a total daily insulin treatment of <1.2 IU/kg/day; and a glycosylated haemoglobin level of ≤10.0 %.
Exclusion criteria for study participation included donation of blood or plasma in the past month or donations of >500 mL within 3 months before screening; use of systemic [oral or intravenous (IV)] corticosteroids, monoamine oxidase inhibitors, non-selective beta-blockers, growth hormone, non-routine vitamins or herbal products; use of thyroid hormones, unless this use had been stable during the previous 3 months; smoking or the use of nicotine gum or transdermal nicotine patches during the inpatient period; recurrent severe hypoglycaemia (more than one severe hypoglycaemic event during the last 12 months); hypoglycaemic unawareness as judged by the investigator; and hospitalisation for diabetic ketoacidosis during the previous 6 months.
Interventions and Pharmacokinetic Sampling
Following screening (Visit 1), subjects were randomly allocated 1:1 to one of two predetermined treatment sequences, each comprising two 6-day treatment periods (Period 1, Visits 2–8; Period 2, Visits 9–15). Each treatment period included once-daily SC dosing with 0.4 U/kg of IDeg or IGlar, in a two-period crossover design. IGlar was included primarily as a control in case differences between age groups were observed for IDeg. As this was not the case, only results from IDeg treatment are reported herein. The two treatment periods were separated by a washout period of 7–21 days, during which time subjects resumed their normal insulin treatment.
IDeg [provided in 3-mL Penfill®
cartridges (100 U/mL)] and IGlar [provided in 3-mL cartridges (100 U/mL)] were administered once daily at approximately 8.00 pm via SC injection into a lifted skin fold on the anterior surface of the thigh using a syringe and needle. This region of injection is commonly used for the injection of basal or long-acting insulin preparations because of the slower absorption from this site [7
]. Doses were prepared by a study nurse not otherwise involved in the trial, to maintain study blinding. During treatment periods, additional control of blood glucose levels was accomplished by bolus injections of insulin aspart, which were administered into a lifted skin fold on the lower abdominal wall and were supervised by the investigator on a daily basis. As a general guidance to serve as a basis for the supervision of the bolus insulin doses, the daily mean pre-prandial plasma glucose values were to be below or equal to 8.0 mmol/L (144 mg/dL). The last injection of insulin aspart was no later than 10 h before dosing on each clamp visit.
Initial dosing in each treatment period took place during Visit 2 (Period 1) and Visit 9 (Period 2), respectively. During these 48-h in-house visits, the first three once-daily doses of IDeg or IGlar were administered at time points 0, 24 and 48 h. Subjects subsequently attended the clinic daily for two further outpatient visits (Visits 3 and 4, and Visits 10 and 11). Blood samples for assessment of pharmacokinetic parameters were taken before the first dosing, at frequent intervals within the first 24 h after the first dosing (at intervals of 0.25–2 h) and immediately before subsequent doses (Visits 3 and 4, and Visits 10 and 11). The final dosing visit was an in-house visit (Visits 5 and 12) during which blood samples for steady-state pharmacokinetic assessment were taken regularly, both before (at hourly intervals from 1 to 5 h pre-dose and at 15 min pre-dose) and for 48 h after dosing (at intervals of 0.5–10 h). Blood samples were also taken for plasma glucose analysis every 5–30 min during this period up to 26 h post-dosing and at 28, 38 and 48 h post-dosing. Subjects were discharged 48 h after final dosing, and returned at 72, 96 and 120 h post-dose (Visits 6–8 and Visits 13–15) for blood sampling for pharmacokinetic and plasma glucose analysis. A final follow-up visit (Visit 16) was conducted 7–21 days after the final dosing visit. The number of dosing days was chosen to ensure that all subjects reached steady state before a euglycaemic clamp was conducted.
Euglycaemic Glucose Clamp Procedure
The steady-state pharmacodynamic effects of IDeg were evaluated using a 26-h euglycaemic clamp procedure [target blood glucose 5.5 mmol/L, (100 mg/dL)], beginning after final dosing, during Visit 5 (Period 1) and Visit 12 (Period 2). In brief, subjects fasted for at least 12 h before dosing and the start of the 26-h clamp, and remained fasted (with water ad libitum) and in a supine position until the clamp procedure was complete. Approximately 5 h before dosing a 3-h clamp run-in period was initiated, during which subjects received a variable IV infusion of human insulin (40 IU Actrapid®, 100 IU/mL in 99.6 mL saline) or glucose (10 %; Braun Infusomat FM, Melsungen, Germany) to obtain the glucose clamp target level of 5.5 mmol/L (100 mg/dL). The target glucose clamp level was maintained during a 2-h pre-dose clamp period leading up to the time of last dose administration. When IV insulin was used during the pre-dose clamp period, the rate of insulin infusion was decreased gradually post-dosing and terminated when glucose levels had declined by approximately 0.3 mmol/L. A variable IV glucose infusion was then initiated to maintain the clamp target level [5.5 mmol/L, (100 mg/dL)]. The clamp was maintained for 26 h after dosing; however, the clamp procedure was terminated early if plasma glucose levels consistently exceeded 11.1 mmol/L (200 mg/dL) without any glucose infusion in the previous 30 min.
Data and Statistical Analyses
The primary objective of the trial was to investigate the pharmacodynamic effects of IDeg at steady state in elderly subjects with type 1 diabetes versus younger adults with type 1 diabetes. Secondary objectives for the two age groups were to investigate the pharmacokinetic and pharmacodynamic profiles, including the pharmacokinetic exposure of IDeg at steady state, time to reach steady state and the safety of IDeg. Pharmacokinetic endpoints for IDeg included the area under the IDeg serum concentration–time curve during one dosing interval at steady state (AUCIDeg,τ,SS) (τ = 0–24 h), the maximum IDeg serum concentration at steady state (Cmax,IDeg,SS) and the ratio between AUCIDeg,0–12h,SS and AUCIDeg,τ,SS (AUCIDeg,0–12h,SS/AUCIDeg,τ,SS). The primary pharmacodynamic endpoint for IDeg was the area under the glucose infusion rate (GIR) curve during one dosing interval at steady state (AUCGIR,τ,SS) (τ = 0–24 h). Secondary pharmacodynamic endpoints included GIRmax,IDeg,SS, the ratio between AUCGIR,0–12h,SS and AUCGIR,τ,SS (AUCGIR,0–12h,SS/AUCGIR,τ,SS), and the duration of action of IDeg (time from dose administration until the plasma glucose level increased to a level consistently above 8.3 mmol/L [150 mg/dL], during the glucose clamp procedure).
Safety assessments comprised adverse events (AEs), including local injection-site reactions, laboratory safety variables, physical examination, vital signs, electrocardiogram (ECG) and hypoglycaemic episodes (defined as ‘confirmed’ when they were either ‘severe’ as defined by the American Diabetes Association [8
] or verified by a plasma glucose level of <3.1 mmol/L [56 mg/dL]).
IDeg serum concentrations were measured using a validated IDeg sandwich enzyme-linked immunosorbent assay. AUCIDeg,0–12h,SS and AUCIDeg,τ,SS were calculated as the area under the insulin concentration–time profile using the linear trapezoidal method based on observed values and actual measurement times. Missing values were imputed using linear interpolation. Cmax,IDeg,SS was derived from the individual concentration–time profiles.
AUCGIR,τ,SS was derived from individual GIR profiles and was calculated as the area under the smoothed GIR curve using the linear trapezoidal technique on interpolated points. GIRmax,IDeg,SS was derived from the smoothed GIR curve.
All analyses were conducted on the full analysis set. Log-transformed AUCGIR,τ,SS, GIRmax,IDeg,SS, AUCIDeg,τ,SS and Cmax,IDeg,SS values were analysed using an analysis of variance method with age group (elderly/younger adult) and treatment period (Period 1/Period 2) as fixed factors. Based on this model, age group means for absolute values were estimated and mean age group ratios were estimated together with two-sided 95 % confidence intervals (CIs). Mean AUCIDeg,0–12h,SS/AUCIDeg,τ,SS and AUCGIR,0–12h,SS/AUCGIR,τ,SS were calculated and summarised using descriptive statistics. Safety endpoints were summarised using descriptive statistics.