Pharmacokinetic and Pharmacodynamic Properties of Faster-Acting Insulin Aspart versus Insulin Aspart Across a Clinically Relevant Dose Range in Subjects with Type 1 Diabetes Mellitus

This was a randomised, single-centre (Profil, Neuss, Germany), double-blind, eight-period, crossover trial. The local health authority (Bundesinstitut für Arzneimittel und Medizinprodukte) and an independent ethics committee (Ärztekammer Nordrhein) reviewed and approved the trial protocol. The trial was registered at ClinicalTrials.gov (trial identifier: NCT02033239).

Eligible subjects were men and women 18–64 years of age (both inclusive), with T1DM for ≥12 months before inclusion in the trial, treated with multiple daily insulin injections or continuous subcutaneous insulin infusion for ≥12 months [total daily insulin dose <1.2 (I)U/kg/day and total daily bolus insulin dose < 0.7 (I)U/kg/day], with HbA_1c ≤9.0% (≤75 mmol/mol), body mass index (BMI) of 18.5–28.0 kg/m² (both inclusive) and fasting C-peptide ≤0.3 nmol/L. Subjects were excluded if they had clinically significant concomitant diseases, clinically significant abnormal values in clinical laboratory screening tests, were smokers or were currently treated with other drug(s) that may interfere with glucose metabolism.

Informed consent was obtained from all individual participants included in the study.

The trial consisted of 10 visits: a screening visit, eight dosing visits separated by a 3- to 15-day washout period, and a follow-up visit. All subjects received three dose levels (0.1, 0.2 and 0.4 U/kg) of faster aspart and insulin aspart to compare the pharmacokinetic and pharmacodynamic properties between treatments, and to investigate the dose–concentration and dose–response relationships. To estimate the within-subject variability, subjects were randomised to receive either two additional doses of faster aspart 0.2 U/kg or two additional doses of insulin aspart 0.2 U/kg (Fig. 1). The eight dosing visits were conducted in randomised sequence.

The trial products were faster aspart (100 U/mL; Novo Nordisk, Bagsværd, Denmark) and insulin aspart (NovoRapid^®; 100 U/mL; Novo Nordisk), both in a blinded PDS290 pen-injector prefilled pen (Novo Nordisk). Trial products were administered by subcutaneous injection into a lifted skinfold of the lower abdominal wall above the inguinal area by a qualified person with no other tasks in the study, to keep its double-blind nature.

At each dosing visit, subjects attended the clinical site in the morning after having fasted since 2200 h the evening before (except for water ad libitum and ≤20 g of rapidly absorbable carbohydrate if needed to prevent hypoglycaemia). A euglycaemic glucose clamp procedure (ClampArt^®; Profil) was then conducted as previously described [11]. Initially, subjects received a variable intravenous infusion of regular human insulin [15 IU Actrapid^® (100 IU/mL; Novo Nordisk) in 49 mL saline and 1 mL of the subject’s blood] or glucose (20%) for 1–4 h before dosing to obtain a blood glucose target level of 5.5 mmol/L (100 mg/dL). The intravenous insulin infusion rate was manually adjusted by attending staff based on actual blood glucose measurements, while the intravenous glucose infusion rate was automatically adjusted by ClampArt^® in order to keep blood glucose at the target level throughout the glucose clamp. Dosing of the trial product occurred after blood glucose concentration had been stable for ≥1 h, with no infusion of glucose. After dosing, the rate of intravenous insulin infusion (if any) was gradually reduced and terminated completely when blood glucose had fallen by 0.3 mmol/L (5 mg/dL). The intravenous glucose infusion was then initiated. The clamp lasted for up to 12 h after dosing, but was stopped earlier if blood glucose consistently exceeded 11.1 mmol/L (200 mg/dL) without the need for intravenous glucose infusion during the last 30 min. Mean profiles of intravenous insulin infusion from −60 min until blood glucose had fallen by 0.3 mmol/L (5 mg/dL), and mean profiles of blood glucose concentration from −60 min until 30 min, are shown in Online Resource 1, Fig. S1. The quality of the conducted clamps was high and comparable across treatments and dose levels (Online Resource 1, Table S1) [15].

Blood samples for pharmacokinetic assessment were drawn within 2 min pre-dose, then every 2 min from dosing until 20 min post-dose, every 5 min from 20 to 80 min, every 10 min from 80 min to 2 h, every 15 min from 2 to 2.5 h, and then at 3, 3.5, 4, 5.5, 7, 9 and 12 h post-dose.

Free serum insulin aspart concentrations (polyethylene glycol-precipitated) were measured by a validated insulin aspart-specific enzyme-linked immunosorbent assay with a lower limit of quantification (LLOQ) of 10 pmol/L. The glucose infusion rate needed to keep the blood glucose concentration at the clamp target level was recorded automatically every minute during the glucose clamp. Safety assessments included adverse events, local tolerability at the injection site, hypoglycaemic episodes (defined as ‘confirmed’ when they were either ‘severe’ according to the American Diabetes Association, i.e. requiring third-party assistance [16], or verified by a plasma glucose level of <3.1 mmol/L [56 mg/dL]), laboratory safety parameters, physical examination, vital signs and electrocardiogram.

Endpoints were onset of appearance [time from trial product administration until the first-time serum insulin concentration ≥LLOQ (10 pmol/L)], time to early 50% of maximum insulin concentration (t _{Early 50% Cmax}), time to maximum insulin concentration (t _max), onset of action [time from trial product administration until the blood glucose concentration had decreased by ≥0.3 mmol/L (5 mg/dL) from baseline], time to early 50% of maximum glucose infusion rate (t _{Early 50% GIRmax}), and time to maximum glucose infusion rate (tGIR_max) [all to evaluate onset of exposure and onset of glucose-lowering effect]; early partial areas under the curve (AUCs) for serum insulin (AUC_{IAsp,0–15min}, AUC_{IAsp,0–30min}, AUC_IAsp,0–1h, AUC_{IAsp,0–1.5h}, and AUC_IAsp,0–2h) and glucose infusion rate (AUC_{GIR,0–30min}, AUC_GIR,0–1h, AUC_GIR,0–1.5h, and AUC_GIR,0–2h) to evaluate early exposure and early glucose-lowering effect; and total exposure (AUC_IAsp,0–t ), maximum concentration (C_max), total glucose-lowering effect (AUC_GIR,0–t ; primary endpoint), and maximum glucose infusion rate (GIR_max) to evaluate overall exposure and glucose-lowering effect.

For calculation of onset of appearance and AUC_{IAsp,0–15min}, insulin aspart concentration was imputed during the time interval from dosing until the time of the first observed insulin aspart concentration above LLOQ using compartmental modelling (see Online Resource 1, page 4 for details). For consistency, this approach was also used for the initial part of the AUC in the calculation of all other AUC_IAsp endpoints. AUC_IAsp,0–t was derived by calculating the AUC until the time of the last quantifiable insulin aspart concentration, and then extrapolating until 12 h (last pharmacokinetic sampling time point) based on the terminal slope. AUC_GIR,0–t was calculated until the time of the last observed glucose infusion rate >0. Endpoints were derived from the raw profiles, except for t _{Early 50% GIRmax}, GIR_max and tGIR_max, which were derived from LOESS smoothed glucose infusion rate profiles (using a smoothing factor of 0.1) in order to ensure robust calculation of these endpoints.

Of 53 subjects screened, 46 were randomised and treated and 43 completed the trial (Fig. 1). Two subjects withdrew consent after three and four dosing visits, respectively, and one subject was withdrawn after seven dosing visits due to not being able to attend the next scheduled visit. The mean (±standard deviation) age of the 46 randomised subjects was 44.0 (±10.4) years. The majority of subjects were male (76.1%) and all were White. Mean body weight was 77.4 (±10.8) kg and mean BMI was 24.6 (±2.4) kg/m². Mean duration of diabetes was 20.8 (±10.0) years, and mean HbA_1c at baseline was 7.4% (±0.8%). At entry into the study, 30 subjects were treated with multiple daily injection therapy and 16 subjects used continuous subcutaneous insulin infusion.

A left-shift of the mean serum insulin aspart concentration–time profile was observed for faster aspart compared with insulin aspart at all three dose levels (Fig. 2). Likewise, the glucose-lowering effect profile was shifted to the left for faster aspart versus insulin aspart across the three dose levels (Fig. 3).

Across all three dose levels, onset of appearance occurred approximately twice as fast for faster aspart compared with insulin aspart, and t _{Early 50% Cmax} was also earlier with faster aspart than with insulin aspart (Fig. 4a and Online Resource 1, Table S2). Early insulin exposure was consistently greater for faster aspart than for insulin aspart within the first 30 min after dosing, irrespective of dose level, as shown by the greater AUC_{IAsp,0–15min} and AUC_{IAsp,0–30min} for faster aspart versus insulin aspart (Fig. 5a).

Onset of action occurred 5–6 min faster, and t _{Early 50% GIRmax} also occurred earlier, with faster aspart than with insulin aspart across all three doses (Fig. 4b and Online Resource 1, Table S3). Early glucose-lowering effect was consistently greater for faster aspart than for insulin aspart at all three dose levels, as shown by the greater partial AUC_GIR’s for faster aspart versus insulin aspart within the first 2 h after dosing, except for AUC_{GIR,0–30min} and AUC_GIR,0–2h at 0.1 U/kg (Fig. 5b).

Estimated means as well as treatment ratios and/or differences for faster aspart versus insulin aspart are shown for all pharmacokinetic and pharmacodynamic endpoints in Online Resource 1, Tables S2 and S3.

Mean 5-h serum insulin concentration–time profiles for faster aspart and insulin aspart at 0.1, 0.2 and 0.4 U/kg are presented in Fig. 6 and show that insulin exposure increased with increasing dose. Analysis of dose proportionality for faster aspart indicated that the increases in AUC_IAsp,0–t and C _max with increasing dose of faster aspart were slightly greater than dose proportional, as the mean and 95% CIs for the log-dose slopes were 1.21 (1.15–1.26, p < 0.001) for AUC_IAsp,0–t , and 1.18 (1.10–1.25, p < 0.001) for C _max, i.e. slightly different from 1.00. However, the same was observed for insulin aspart [1.20 (1.14–1.25), p < 0.001, for AUC_IAsp,0–t ; and 1.08 (1.00–1.16), p = 0.052, for C _max], and the departures from dose proportionality did not differ statistically significantly between faster aspart and insulin aspart for AUC_IAsp,0–t (p = 0.809) or C _max (p = 0.094). In quantitative terms, a log-dose slope of 1.21 corresponds to a 12% increase in total exposure following a 10% increase in the faster aspart dose.

Mean 5-h glucose infusion rate profiles for faster aspart and insulin aspart at 0.1, 0.2 and 0.4 U/kg are presented in Fig. 7 and show that the glucose-lowering effect increased with increasing dose. The total glucose-lowering effect (AUC_GIR,0–t ) for both faster aspart and insulin aspart was approximately twice as high at the 0.2 U/kg dose than at the 0.1 U/kg dose (Table 1). In contrast, AUC_GIR,0–t for the 0.4 U/kg dose was only 73% larger than for the 0.2 U/kg dose level for both faster aspart and insulin aspart, i.e. less than expected for a doubling of the dose. The estimates of GIR_max also showed a levelling off with increasing dose for both treatments (Online Resource 1, Table S3), suggesting that some subjects approached a maximum plateau of insulin action at the higher insulin dose of 0.4 U/kg. Accordingly, analysis of dose linearity indicated that the increases in AUC_GIR,0–t and GIR_max with increasing dose were slightly less than linear (p < 0.01 for AUC_GIR,0–t , and p < 0.001 for GIR_max). The coefficients of the function describing the dose–response relationship were not statistically significantly different between faster aspart and insulin aspart for AUC_GIR,0–t (p = 0.786) and GIR_max (p = 0.944).

Within-subject day-to-day variability for faster aspart was low for early, total and maximum glucose-lowering effect, and did not differ statistically significantly from insulin aspart (Table 2). Results on between-subject variability for early, total and maximum glucose-lowering effect are provided in Online Resource 1, Table S4, and showed no statistically significant differences between faster aspart and insulin aspart.

The estimated treatment ratio and 90% CI of faster aspart versus insulin aspart for AUC_IAsp,0–t for all three dose levels together were 0.97 (0.94–1.01). Thus, the bioavailability of faster aspart was similar to insulin aspart as the 90% CI for AUC_IAsp,0–t was fully within the interval of 0.80–1.25.

AUC_GIR,0–t and GIR_max were both comparable for faster aspart and insulin aspart at all three dose levels, with all treatment ratios being close to 1.00 (Online Resource 1, Table S3), suggesting similar total glucose-lowering effects for faster aspart and insulin aspart when administered at identical dose levels.

The relationships between total exposure (AUC_IAsp,0–t ) and total glucose-lowering effect (AUC_GIR,0–t ), and between C _max and GIR_max, for faster aspart are presented in Online Resource 1, Fig. S2. From the coefficient of determination (R ²), approximately 50% of the variability in total and maximum glucose-lowering effect could be explained by total exposure and maximum concentration, respectively.

Both faster aspart and insulin aspart were well tolerated and no safety issues were observed during the trial. There were no clinically significant findings in safety laboratory parameters, vital signs, physical examination or electrocardiogram, and no confirmed hypoglycaemic episodes or injection site reactions occurred during the trial.