Distinct Prandial and Basal Glucose-Lowering Effects of Insulin Degludec/Insulin Aspart (IDegAsp) at Steady State in Subjects with Type 1 Diabetes Mellitus

This single-center, single-arm, open-label trial was registered with clinicaltrials.gov (NCT01590836), and the protocol was reviewed and approved by the local health authority (Bundesinstitut für Arzneimittel und Medizinprodukte) in accordance with regulations, and by the appropriate ethics committee (Ärztekammer Nordrhein). All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 and 2008. Informed consent was obtained from all patients for being included in the study. The study was performed in accordance with Good Clinical Practice as defined by the International Conference on Harmonisation. Subjects were fully informed of the risks of the trial and were made aware that they could withdraw from the trial at any time for any reason. Patients were informed verbally and in writing, and written consent was obtained before any trial-related procedures were initiated.

Trial participants included 22 men and women aged 18–65 years, with T1DM, treated with insulin for at least 12 months with a current daily basal insulin requirement of ≥0.2 U/kg/day and a total insulin dose of <1.2 U/kg/day. Eligible subjects were also required to have a body mass index (BMI) in the range of 18.0–28.0 kg/m², an HbA_1c level of ≤9.5%, and a fasting C-peptide level of ≤0.3 nmol/L.

Subjects were excluded from participation if they had a history or presence of cancer or cardiovascular disease, supine blood pressure beyond the normal range (90–140 mmHg systolic; 50–90 mmHg diastolic), proliferative retinopathy or maculopathy and/or severe neuropathy, recurrent severe hypoglycemia (more than one episode requiring assistance in the past 12 months) or hypoglycemia unawareness, or smoked >5 cigarettes or the equivalent, per day.

The trial consisted of a screening visit (Visit 1), followed by a treatment period (Visits 2–8), and a follow-up visit (Visit 9). After screening, all subjects received IDeg (0.42 U/kg) once daily for 5 days to reach steady state [20]. IAsp was given as required, which enabled individualization of bolus doses on Days 1–5 (IAsp has a short exposure and therefore does not accumulate over time). On Day 6, subjects received a single dose of IDegAsp (0.6 U/kg, comprising 0.42 U/kg IDeg and 0.18 U/kg IAsp). At each dosing visit, trial product was administered at approximately 8 p.m. This time was chosen for convenience in performing the clamp procedure and does not reflect requirements in normal clinical practice.

IDeg and IDegAsp were dosed as subcutaneous injections into a lifted skinfold of the lower abdominal wall above the inguinal area. Both were provided in 3 mL Penfill^® cartridges (Novo Nordisk, Bagsvaerd, Denmark) (100 U/mL) and administered using a syringe and needle.

After administration of IDegAsp on Day 6, the steady-state pharmacodynamic response was evaluated using a 30-h euglycemic glucose clamp performed with a Biostator^® device (MTB Medizintechnik, Amstetten, Germany), as described previously [18]. In brief, 5–6 h before dosing of the trial product, subjects received a variable intravenous infusion of human insulin (15 IU Actrapid^®, 100 IU/mL in 49 mL saline and 1 mL of the subject’s blood) or glucose to obtain a blood glucose clamp target level of 5.5 mmol/L (100 mg/dL). After trial product administration, when only insulin was infused to maintain the glucose clamp target, the rate of insulin infusion was decreased gradually and stopped completely when blood glucose had decreased by 0.3 mmol/L (5 mg/dL); glucose infusion was then initiated to keep the glucose concentration constant at the glucose clamp target of 5.5 mmol/L (100 mg/dL). The clamp continued for 30 h post-dosing of trial product, but was terminated earlier if the blood glucose consistently exceeded 13.9 mmol/L (250 mg/dL) without any glucose having been administered for at least 30 min. During the entire clamp procedure, subjects remained fasting (with no oral intake other than water) and stayed in a supine or semi-supine position.

The glucose infusion rate (GIR) required to keep the blood glucose concentration at the target level was recorded every minute throughout the euglycemic clamp. Approximately every 30 min throughout the glucose clamp, blood glucose measurements from the Biostator were checked against blood glucose measurements performed by a glucose analyzer (Super GL Glucose Analyzer, Hitado, Möhnesee, Germany). Blood samples for determination of serum IAsp concentration were taken on Day 6 at the following times: 5 min predose, 0 min, at 10 min intervals until 2 h post-dose, then every 15 min to 3 h, then at 3½, 4, 5, 6, 8, 10, 11 and 12 h post-dose. Serum IDeg concentrations were measured in blood samples taken 5 min predose and at 0 min on Days 1–5 then on Day 6, at 5 min predose, 0 min, 30 min, 1 h and thereafter every hour until 16 h, then at 18, 20, 22, 24, 30, 36 and 48 h.

Each subject remained in the clinic for 48 h after IDegAsp dosing. Subjects returned to the clinic at time points 72, 96 and 120 h after dosing to have blood samples taken for pharmacokinetic assessment of IDeg and for monitoring of blood glucose.

Serum IAsp concentrations were quantified using a validated IAsp-specific enzyme-linked immunosorbent assay (ELISA). Serum IDeg concentrations were measured using a validated IDeg-specific sandwich ELISA.

The primary endpoint was the total glucose-lowering effect estimated by the area under the GIR curve during one 24-h dosing interval at steady state (AUC_GIR,τ,SS) after administration of IDegAsp.

Secondary endpoints included time to GIR_max,SS (t _GIRmax,SS), duration of action of IDegAsp, total exposure of IDeg (AUC_IDeg,τ,SS) and distribution of IDeg exposure over the 24-h dosing interval at steady state (AUC_{IDeg,0–12h,SS}/AUC_IDeg,τ,SS), total exposure of IAsp (AUC_IAsp,0–12h), and time to maximum observed serum concentration of IAsp (t _max,IAsp). In addition, using the data obtained from once-daily dosing in this trial, a pharmacokinetic/pharmacodynamic model was used to simulate steady-state GIR response following twice-daily dosing of IDegAsp.

Safety was monitored for both IDeg and IDegAsp administration. Safety endpoints included treatment-emergent adverse events, confirmed hypoglycemic episodes, physical examination, vital signs, electrocardiogram (ECG), and clinical laboratory values. Confirmed hypoglycemia was defined as any episode of severe hypoglycemia (as per the American Diabetes Association definition [21]) or minor hypoglycemia [plasma glucose <3.1 mmol/L (56 mg/dL) or blood glucose <2.8 mmol/L (50 mg/dL)].

Pharmacokinetic and pharmacodynamic analyses were based on the full analysis set, which included 22 subjects. The primary endpoint, AUC_GIR,τ,SS, was derived from individual GIR profiles and calculated as the area under the smoothed GIR profile using the linear trapezoidal technique on interpolated data points.

Secondary pharmacodynamic endpoints were derived from individual GIR profiles (smoothed) and blood glucose profiles at steady state. Duration of action was calculated as the time from administration of IDegAsp until blood glucose concentration was consistently >8.3 mmol/L (end of action) during the euglycemic glucose clamp at steady state [22]. Statistical analyses were performed using SAS^® 9.1.3 software (SAS Institute Inc., Cary, NC, USA).

The pharmacokinetic/pharmacodynamic model used to simulate steady-state GIR response consisted of separate pharmacokinetic and pharmacodynamic components for IDeg and for IAsp. For IDeg, the pharmacokinetic component was based on absorption (with a depot compartment and a transit compartment, an absorption-rate parameter and a transit-rate parameter), and disposition (with a single distribution compartment, a clearance parameter, and a volume-of-distribution parameter), and the pharmacodynamic component linked the concentration in the distribution compartment to GIR by means of an insulin-action compartment, a turnover parameter, and an insulin-sensitivity parameter. For IAsp, the pharmacokinetic component was based on absorption (with a depot compartment and four transit compartments, an absorption-rate parameter, and a transit-rate parameter), and disposition (with a single distribution compartment, a clearance parameter, and a volume-of-distribution parameter), and the pharmacodynamic component linked the concentration in the distribution compartment to GIR by means of an insulin-action compartment, a turnover parameter, and an insulin-sensitivity parameter. The GIR contributions for IDeg and IAsp were subsequently added to simulate total GIR effect. The parameters of the model were estimated in a population pharmacokinetic/pharmacodynamic setting, using a nonlinear mixed-effects approach, which allowed individual sets of parameters to be obtained for each of the subjects included in the trial. Using the estimated individual parameters, a simulation of twice-daily multiple dosing was conducted to obtain a mean steady-state profile. Twice-daily multiple dosing for 6 days at a dose level of 0.3 U/kg was simulated for each of the subjects, and the mean of the profiles on Day 6 was subsequently calculated. A dose of 0.3 U/kg was used for the simulation based on the assumption that the once-daily dose of 0.6 U/kg would be divided into two for the twice-daily dose. The modeling was performed using NONMEM^® version 7.1.2 (ICON Development Solutions, Ellicott City, MD, USA) and the corresponding figure was produced using S-Plus version 8.2 (TIBCO, Palo Alto, CA, USA).

Safety analyses were based on the safety analysis set (all subjects who received ≥1 dose of either IDeg or IDegAsp). Safety endpoints were summarized using descriptive statistics.

Of the 25 subjects screened, a total of 22 subjects (18 men, 4 women) with T1DM were exposed to IDeg and IDegAsp during the trial. No subjects withdrew from the trial. The mean age of the subjects was 40 years (range 20–56 years), mean HbA_1c was 7.9% (range 5.8–9.0%), mean duration of diabetes was 23.1 years (range 8.9–42.9 years), and mean BMI was 24.6 kg/m² (range 20.2–27.9 kg/m²) (Table 1).

The mean GIR profile at steady state is shown in Fig. 2, reflecting the primary endpoint, AUC_GIR,τ,SS [geometric mean (coefficient of variation): 3,859 mg/kg (33%)]. The profile showed a rapid onset of action and a distinct peak due to the IAsp component, and a separate, stable basal glucose-lowering effect attributable to the IDeg component. The median t _GIRmax,SS for IDegAsp was 2.5 h. The clamp was performed when steady state of the basal component had been established. The GIR was already elevated at the time of injection of IDegAsp, owing to the duration of action of IDeg being >42 h [13], so that the effect of the previous IDeg injections on Days 1–5 was expected to elicit a GIR response already at time-point 0 on Day 6.

Mean blood glucose levels remained at the clamp target level throughout the euglycemic clamp procedure (Fig. 3). No subject experienced end of action (defined as a blood glucose level >8.3 mmol/L) or early termination during the 30-h clamp, hence the duration of action of IDegAsp extended beyond 30 h in all 22 subjects.

The model simulating the pharmacodynamic response to twice-daily dosing of IDegAsp at steady state indicated that the distinct peak (due to IAsp) and the separate, flat basal action (due to IDeg) were retained following each dose (Fig. 4).

Mean total serum exposure of IAsp in IDegAsp (AUC_IAsp,0–12h) was 1,087 pmol h/L. The IAsp component of IDegAsp had a rapid onset of appearance; t _max,IAsp was 80 min (median). The mean total serum exposure of IDeg in IDegAsp (AUC_IDeg,τ,SS) at steady state, during one dosing interval, was 72,084 pmol h/L. Exposure to the IDeg component of IDegAsp was similar in the first and second 12 h periods. The mean ratio of AUC_{IDeg,0–12h,SS}/AUC_IDeg,τ,SS was 0.51, indicating that IDeg has an evenly distributed pharmacokinetic profile over 24 h at steady state. Clinical steady state was achieved after 2–3 days of once-daily IDeg dosing.

During 5 days of IDeg administration, one adverse event was reported that was considered possibly related to IDeg treatment—a case of mild headache. Furthermore, while IDeg steady state was being attained, there were 22 confirmed hypoglycemic episodes in 13 subjects.

After administration of IDegAsp on Day 6, there were no reported AEs that were considered to be related to IDegAsp. A total of six confirmed hypoglycemic episodes were recorded in five subjects after administration of IDegAsp on Day 6. Four occurred 30–48 h after IDegAsp administration, and the other two occurred 96–120 h after IDegAsp administration. These hypoglycemic episodes may therefore have been related to the administration of bolus insulin or the switch to other regimens following cessation of IDegAsp treatment.

There were no significant treatment-emergent changes in clinical laboratory parameters, vital signs, physical examination or ECG findings following subcutaneous IDeg and IDegAsp administration. No injection site reactions were reported during the trial.