Comparative evaluation of pharmacokinetics and pharmacodynamics of insulin glargine (Glaritus®) and Lantus® in healthy subjects: a double-blind, randomized clamp study

Pharmacokinetics, Pharmacodynamics, and Bioequivalence of Test Insulin Glargine Versus Reference Preparation (Lantus®) in Healthy Male Volunteers-By Euglycemic Clamp Technique

The aim of this study was to evaluate the pharmacokinetics (PK), pharmacodynamics (PD), and safety of two insulin glargine preparations in healthy Chinese male subjects. Methods: Forty healthy Chinese male subjects were enrolled in this randomized, open, two-sequence, four-period, single-dose, crossover study and were randomly divided into RTRT or TRTR (first-period injection of test preparation, second-period injection of reference preparation, third-period injection of test preparation, fourth-period injection of reference preparation) groups. A 24 h euglycemic clamp test measured GIR. Plasma insulin glargine concentration and C-peptide were collected during the trial and analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and enzyme-linked immunosorbent assay (ELISA). WinNonLin calculated PD/PK parameters and the equivalence of the two preparations was testified by SAS9.2. Results: The average concentration of C-peptide was lower than the baseline and the blood glucose was close to the targeted value in each sequence. PK parameters cmax of the test and the reference preparation insulin glargine were 0.580 and 0.614 ng·mL-1, and the AUC0-24h were 9.782 and 10.436 h·ng·mL-1, respectively. PD parameters GIRmax were 42.748 and 45.279 mg·kg-1·min-1, and AUCGIR,0-24h were 2.924 and 3.096 h·mg·kg-1·min-1, respectively. There was no clinically significant adverse reaction observed during the experiment. Conclusions: The glucose clamp has been established and bioequivalence between test preparation and reference preparation has been demonstrated.

Comparing the Efficacy of Various Insulin Types: Pharmacokinetic and Pharmacodynamic Modeling of Glucose Clamp Effects in Healthy Volunteers

This study compares the pharmacokinetics and efficacy of various subcutaneously (SC) dosed insulin analogs, including rapid-acting, intermediate-acting, long-acting, and regular human insulin, using mechanistic pharmacokinetic (PK) and pharmacodynamic (PD) models. These models were applied to data from euglycemic clamp studies in healthy volunteers, where insulin pharmacokinetics and its effects on glucose utilization were monitored. Data from published studies were digitized and modeled using MONOLIX (Version 2024). The PK model described insulin absorption via sequential first-order processes and linear elimination. The PD effects were captured using a model combination of biophase, indirect, and receptor down-regulation components. While PK parameters-especially absorption rates-varied between insulin types, a common set of nonlinear PD parameters was sought to account for dose-related differences in glucose utilization. The maximum glucose stimulation (S max ${{{\mathrm{S}}}_{{\mathrm{max}}}}$ ) was 163, and the insulin concentration for a half-maximal effect (S C 50 ${\mathrm{S}}{{{\mathrm{C}}}_{50}}$ ) were 1156 pmol/L for insulin lispro, regular human insulin, neutral protamine hagedorn (NPH) insulin, and insulin glargine; 674 pmol/L for insulin aspart; and 5335 pmol/L for insulin detemir. Insulin detemir showed similar overt effects as the other insulin types but with smaller clearances and lower potency. This mechanism-based glucose-insulin model demonstrated that most insulin analogs exhibit similar receptor- and transporter-related parameters. The model, with specific PK but unified PD parameters, may enable clinical optimization of insulin therapy by highlighting differences in pharmacokinetics and operating common intrinsic glucose utilization parameters.

Impact of setting distinct target blood glucose levels on endogenous insulin suppression and pharmacodynamics of insulin preparations

BACKGROUND

Insulin therapy plays a crucial role in managing diabetes. Regulatory guidelines mandate assessing the pharmacokinetics (PK) and pharmacodynamics (PD) of new insulin formulations with euglycemic clamp techniques before entry into the market. Typically, blood glucose (BG) levels are maintained at 5% below baseline to suppress endogenous insulin secretion in healthy volunteers. However, in scenarios where BG baseline is relatively low, maintaining it at 5% below baseline can increase hypoglycemic risk. Consequently, we adjusted to maintain it at 2.5% below a baseline of < 4.00 mmol/L. It remains uncertain whether this adjustment impacts endogenous insulin inhibition or the PD of study insulin.

AIM

To evaluate and compare the PD and C-peptide status using two different target BG setting methods.

METHODS

Data came from euglycemic clamp trials assessing the PK/PD of insulin aspart (IAsp) in healthy participants. Target BG was set at 2.5% below baseline for those with a basal BG of < 4.00 mmol/L (group A), and at 5% below baseline for others (group B). The area under the curve (AUC) of IAsp (AUCIAsp, 0-8 h) and GIR from 0 to 8 hours (AUCGIR, 0-8 h) was used to characterize the PK and PD of IAsp, respectively. The C-peptide reduction and PK/PD of IAsp were compared between the two groups.

RESULTS

Out of 135 subjects, 15 were assigned to group A and 120 to group B; however, group B exhibited higher basal C-peptide (1.59 ± 0.36 vs 1.32 ± 0.42 ng/mL, P = 0.006). Following propensity score matching to adjust for basal C-peptide differences, 71 subjects (15 in group A and 56 in group B) were analyzed. No significant differences were observed in demographics, IAsp dosage, or clamp quality. Group B showed significantly higher baseline (4.35 ± 0.21 vs 3.91 ± 0.09 mmol/L, P < 0.001), target (4.13 ± 0.20 vs 3.81 ± 0.08 mmol/L, P < 0.001), and clamped (4.10 ± 0.17 vs 3.80 ± 0.06 mmol/L, P < 0.001) BG levels. Both groups exhibited comparable C-peptide suppression (32.5% ± 10.0% vs 35.6% ± 12.1%, P = 0.370) and similar IAsp activity (AUCGIR, 0-8 h: 1433 ± 400 vs 1440 ± 397 mg/kg, P = 0.952) under nearly equivalent IAsp exposure (AUCIAsp, 0-8 h: 566 ± 51 vs 571 ± 85 ng/mL × h, P = 0.840).

CONCLUSION

Maintaining BG at 2.5% below a baseline of < 4.00 mmol/L did not compromise the endogenous insulin suppression nor alter the observed pharmacodynamic effects of the study insulin.

How to improve the quality of euglycemic glucose clamp tests in long-acting insulin studies

BACKGROUND

The euglycemic clamp test stands as the best method for assessing the pharmacokinetic and pharmacodynamic properties of long-acting insulin. However, despite its widespread use, there remains a notable absence of an established gold standard for evaluating the test's quality. Existing recommendations from regulatory agencies lack specific threshold values, particularly concerning long-acting insulin. This study aimed to determine the evaluation criteria for assessing the quality of the long-acting insulin euglycemic glucose clamp test and to improve the overall quality of this testing method.

METHODS

Fifty-three healthy volunteers were administered a single dose of insulin degludec (0.4 IU/kg) and underwent a 24-h euglycemic clamp test. Blood samples were collected to evaluate the pharmacokinetics and pharmacodynamics of insulin degludec. Volunteers were separated into group A (coefficient of variation in blood glucose [CVBG] ≤ 3.5%) and group B (CVBG > 3.5%). The quality difference of the clamp test between the groups was assessed using various quality control indices. Volunteers were also categorized into group C (C-peptide reduction rate < 50%) and group D (C-peptide reduction rate ≥ 50%). The clamp test quality, pharmacokinetics, and pharmacodynamics of groups C and D were compared.

RESULTS

According to CVBG, group A had a mean CVBG of 2.95%, group B had a mean CVBG of 4.15%, and group A had a significantly lower CVBG than group B (p < 0.001). CVBG was positively correlated with other quality control indicators, such as the percentage of glucose excursion from the target range (GEFTR), duration of GEFTR, and area under the curve (AUC) of GEFTR. According to the reduction of C-peptide levels: group D had significantly higher C-peptide reduction than group C (p < 0.001). Groups C and D had CVBG < 3.5%. The quality of groups C and groups D was evaluated by the quality control indicators of the clamp test. Only the AUC of GEFTR was statistically different between Groups C and D (p = 0.043, < 0.05), and there was no statistical difference in other indicators between the two groups.

CONCLUSIONS

CVBG could be used as a standard for evaluating the quality of long-acting insulin euglycemic glucose clamp test, and the test quality was superior with a CVBG ≤ 3.5%. A C-peptide reduction ratio ≥ 50% indicated sufficient endogenous insulin inhibition; however, when the glucose fluctuation is small (CVBG is maintained at a low level) during the clamp test, even if the clamp test quality is slightly different, it is not sufficient to interfere with endogenous insulin secretion.

Evaluation of pharmacokinetic and pharmacodynamic similarity of an IDegAsp biosimilar versus the originator in healthy Chinese volunteers

OBJECTIVES

22011 is an insulin degludec/insulin aspart co-formulation (IDegAsp) that shares an identical amino acid sequence with Ryzodeg, the originator IDegAsp. This study aimed to compare the pharmacokinetics (PK), pharmacodynamics (PD), and safety of 22011 with Ryzodeg.

METHODS

In a single-center, randomized, open-label, two-treatment, two-period, two-sequence, crossover, euglycemic clamp study, healthy Chinese adults were randomized to receive 0.5 U/kg of 22011 and Ryzodeg under fasting conditions. PK was evaluated for up to 120 h and PD (represented by glucose infusion rate [GIR]) was assessed for up to 24 h.

RESULTS

Of 46 subjects randomized, all completed both treatment periods and were included in the PK/PD and safety analysis set. Insulin exposure (AUCIDeg, 0-24 h, AUCIAsp, 0-12 h, and Cmax, IAsp) and activity (GIRmax and AUCGIR, 0-24 h) were comparable (estimates of treatment ratios 0.916 ~ 1.076 for primary PK parameters and 0.946 ~ 1.037 for primary PD parameters), with 90% confidence intervals for the ratios of least square means falling within the range of 0.80 ~ 1.25. Adverse events were similar for both products and no significant safety concerns were noted in the laboratory results, vital signs, or electrocardiogram.

CONCLUSION

This study demonstrated the PK/PD similarity of 22011 to Ryzodeg with a comparable safety profile.Trial Registration: http://www.chinadrugtrials.org.cn/index.html with an identifier of CTR20230678, registered 15 March 2023.

A comparative evaluation of bioequivalence of Gan & Lee glargine U300 and Toujeo® in Chinese healthy male participants

Background

To assess the bioequivalence between Gan & Lee (GL) glargine U300 and Toujeo® regarding pharmacokinetics (PK), pharmacodynamics (PD), and safety in Chinese healthy male participants.

Methods

A single-center, randomized, double-blind, single-dose, two-preparation, two-sequence, four-cycle repeated crossover design study was performed to compare GL glargine U300 and Toujeo® in 40 healthy participants. The primary PK endpoints were the area under the curve of glargine metabolites, M1 concentration from 0 to 24 hours (AUC0-24h), and the maximum glargine concentration within 24 hours post-dose (Cmax). The primary PD endpoints were the area under the glucose infusion rate (GIR) curve from 0 to 24 hours (AUCGIR.0-24h) and the maximum GIR within 24 hours post-dose (GIRmax).

Results

GL Glargine U300 demonstrated comparable PK parameters (AUC0-24h, Cmax, AUC0-12h, and AUC12-24h of M1) and PD responses [AUCGIR.0-24h, GIRmax, AUCGIR.0-12h, and AUCGIR.12-24h] to those of Toujeo®, as indicated by 90% confidence intervals ranging from 80% to 125%. No significant disparities in safety profiles were observed between the two treatment groups, and there were no reported instances of serious adverse events.

Conclusion

The PK, PD, and safety of GL glargine U300 were bioequivalent to that of Toujeo®.

Clinical trial registration

https://www.chinadrugtrials.org.cn/, identifier CTR20212419.

A phase-I randomized euglycemic clamp study to demonstrate the pharmacokinetic and pharmacodynamic equivalence of an insulin degludec biosimilar (B01411) with the reference product in healthy Chinese volunteers

BACKGROUND

B01411 is a biosimilar candidate manufactured by Jilin Huisheng Biopharmaceutical Co. Ltd for the reference insulin degludec (Tresiba) (IDeg). This study aimed to evaluate the pharmacokinetics (PK), pharmacodynamics (PD), and safety of the two IDeg products and to assess the PK/PD similarity of B01411 compared with the reference IDeg product.

RESEARCH DESIGN & METHODS

A single-center, single-dose, randomized, crossover, open-labeled, phase I, euglycemic clamp study in healthy Chinese subjects to examine the bioequivalence of B01411 (0.4 U/kg) compared with the reference IDeg product. Blood samples were collected at a predefined time for the analysis of blood glucose (BG), IDeg, and C-peptide concentrations. The glucose infusion rate (GIR) was adjusted to maintain the BG at approximately 0.28 mmol/L below baseline throughout the clamp.

RESULTS

Thirty-two subjects (20 males and 12 females) were enrolled, 31 of whom received both treatments. The 90% confidence intervals for the ratio of the least-squares geometric means for AUCIDeg,0-24 h, AUCGIR,0-24 h, IDegmax, and GIRmax were all in the range of 0.80-1.25. Only one adverse event of puncture site bruising occurred once in a subject in the B01411 group.

CONCLUSION

B01411 exhibited a pharmacokinetic and pharmacodynamic similarity to the reference product. Both IDeg products were well tolerated.

CLINICAL TRIAL REGISTRATION

http://www.chinadrugtrials.org.cn/index.html#. Identifier is CTR20192122.

Pharmacokinetic and pharmacodynamic similarity evaluation between an insulin glargine biosimilar product and Lantus® in healthy subjects: Pharmacokinetic parameters of both parent insulin glargine and M1 were used as endpoints

Insulin glargine is a long-acting insulin analog, which plays an important role in the treatment of diabetes mellitus. Biosimilar products of insulin glargine can provide patients with additional safe, high-quality, and potentially cost-effective options for treating diabetes. This article presents a randomized, double-blind, single-dose, two-treatment, four-period, replicate crossover, euglycemic clamp study which was designed to evaluate the PK and PD similarity between the recombinant insulin glargine developed by Wanbang (test) and Lantus® (reference) in healthy volunteers. Subjects received subcutaneous administration of the insulin glargine formulation (0.4 U/kg) on two occasions for the test and reference drug, respectively, and a 20% dextrose solution was infused at variable rate to clamp the blood glucose concentrations at 0.3 mmol/L below the subjects’ fasting glucose for 24 h. Taking advantage of the improved sensitivity of the bioanalytical method applied and the solution of the matrix stability problem, the parent insulin glargine was determined in the vast majority of plasma samples using a fully validated UHPLC-MS/MS method. The PK characteristics of the parent insulin glargine were revealed for the first time: after subcutaneous injection, concentrations of the parent insulin glargine increased to a relative high level within 3 h, and then, a relatively flat concentration–time profile lasting for at least 12 h post-dose was observed. For the first time, the pharmacokinetic parameters of the parent insulin glargine were used as endpoints for similarity evaluation, which complied with the regulatory guidance better and made the similarity conclusion more powerful. The ratios of geometric means of all PK and PD endpoints were close to 100.00%. For the PK endpoints (AUC0–24h, Cmax, AUC0–12h, and AUC12–24h of the parent insulin glargine and its metabolite M1), the 90% confidence intervals of geometric mean ratios of test to reference were entirely contained within 80.00%–125.00%. For the PD endpoints [AUCGIR(0–24h), GIRmax, AUCGIR(0–12h), and AUCGIR(12–24h)], the 95% confidence intervals of geometric mean ratios of test to reference were entirely contained within 80.00%–125.00%. Based on the above mentioned results, it can be concluded that the PK and PD characteristics of the biosimilar drug developed by Wanbang are similar to those of Lantus.

How to Achieve Sufficient Endogenous Insulin Suppression in Euglycemic Clamps Assessing the Pharmacokinetics and Pharmacodynamics of Long-Acting Insulin Preparations Employing Healthy Volunteers

The therapeutic effect of basal insulin analogs will be sustained at a rather low insulin level. When employing healthy volunteers to assess the pharmacokinetics (PK) and pharmacodynamics (PD) of long-acting insulin preparations by euglycemic clamp techniques, endogenous insulin cannot be ignored and sufficient endogenous insulin inhibition is crucial for the PD and/or PK assessment. This study aimed to explore a way to sufficiently inhibit endogenous insulin secretion. Healthy Chinese male and female volunteers were enrolled. After a subcutaneous injection of insulin glargine (IGlar) (LY2963016 or Lantus) (0.5 IU/kg), they underwent a manual euglycemic clamp for up to 24 h where the target blood glucose (BG) was set as 0.28 mmol/L below the individual’s baseline. Blood samples were collected for analysis of PK/PD and C-peptide. The subjects fell into two groups according to the reduction extent of postdose C-peptide from baseline. After matching for the dosage proportion of Lantus, there were 52 subjects in group A (C-peptide reduction&lt;50%) and 26 in group B (C-peptide reduction≥50%), respectively. No significant difference was detected in age, body mass index, the proportion of Latus treatment and female participants. A lower basal BG was observed in group B compared to group A (4.35 ± 0.26 vs. 4.59 ± 0.22 mmol/L, p &lt; 0.05). The clamp studies were all conducted with high quality (where BG was consistently maintained around the target and exhibited a low variety). The binary logistic regression analysis indicated low basal BG as an independent factor for the success of sufficient endogenous insulin suppression. In conclusion, setting a lower sub-baseline target BG (e.g., 10% instead of 5% below baseline) might be an approach to help achieve sufficient endogenous insulin suppression in euglycemic clamps with higher basal BG levels (e.g., beyond 4.60 mmol/L).

Effects of Unsuppressed Endogenous Insulin on Pharmacokinetics and/or Pharmacodynamics of Study Insulin in the Healthy: A Retrospective Study

C‐peptide, a marker of endogenous insulin, should be consistently inhibited during euglycemic clamping, while an elevated postdosing C‐peptide (CP_postdosing) is not an occasional phenomenon. This was a retrospective study that included 33 men who underwent a manual euglycemic clamp with a subcutaneous injection of insulin aspart (IAsp) aiming to describe the effects of insufficient suppression of endogenous insulin on estimates of the pharmacokinetics and pharmacodynamics of injected insulin. The time profiles of whole blood glucose, human insulin, glucose infusion rate (GIR), and C‐peptide were recorded. The subjects were divided into 2 groups at a ratio of 2:1: group A ([CP_postdosing]_max>baseline CP [CP_baseline]), group B ([CP_postdosing]_max ≤ CP_baseline). The endogenous insulin was approximately equal to the measured value of human insulin or calculated from the C‐peptide. The basal glucose, CP_baseline, basal human insulin, homeostatic model assessment of insulin resistance, IAsp dose, and demographic statistics were all comparable between the 2 groups except the “clamped” glucose. The average clamped glucose was 99.7% (group A) and 94.9% (group B) of baseline. After correction for clamped glucose, GIR area under the concentration‐time curve from time 0 to 8 hours was higher in group A (P < .05) under comparable IAsp exposure. Endogenous insulin area under the concentration‐time curve from time 0 to 8 hours calculated from C‐peptide was different from that measured from human insulin in group A (P < .05), whereas no statistical difference between these measures was observed in group B. Hence, blood glucose should be controlled below the baseline to ensure the inhibition of endogenous insulin. Unsuppressed endogenous insulin may contribute to observed GIR, and the endogenous insulin–corrected pharmacokinetics estimated by C‐peptide may be inaccurate with insufficient endogenous insulin suppression.

Reduction in C-Peptide Levels and Influence on Pharmacokinetics and Pharmacodynamics of Insulin Preparations: How to Conduct a High-Quality Euglycemic Clamp Study

Objective: The aim of the study was to investigate the different extent of inhibition of endogenous insulin secretion by the reduction of C-peptide levels in an euglycemic clamp study and its effects on the evaluation of pharmacokinetics, pharmacodynamics of insulin preparations, and quality of clamp study to determine the best reduction range of C-peptide levels. Methods: Healthy Chinese male volunteers were enrolled and underwent a single-dose euglycemic clamp test. Participants were subcutaneously injected with long-acting insulin glargine (0.4 IU/kg). Blood samples were collected pretest and up to 24 h post-test to assess pharmacokinetics (PK), pharmacodynamics (PD), and C-peptide levels. Results: We divided the 39 volunteers enrolled in the study into three groups according to the reduction of C-peptide levels: group A (ratio of C-peptide reduction <30%, n = 13), group B (ratio of C-peptide reduction between ≥ 30% and <50%, n = 15), and group C (ratio of C-peptide reduction ≥50%, n = 11); there were significant differences in the three groups (p = 0.000). The upper and lower limits of blood glucose oscillation in group C was statistically lower than the other groups, the range of oscillating glucose levels in group C was -17.0 ± 6.6% to -1.1 ± 6.7%. The AUC_0-24 h in groups A, B, and C were 9.7 ± 2.2, 11.0 ± 2.9, and 11.9 ± 2.1 ng/ml × min, respectively, which indicated an increasing trend in the three groups (P _trend = 0.041). For quality assessment, the average glucose (p = 0.000) and MEFTG (p = 0.001) levels in three groups were significantly different. Conclusion: The different extent of inhibition of endogenous insulin will influence the PK/PD of insulin preparations and the quality of the euglycemic clamp. Furthermore, the ratio of C-peptide reduction should be above 50% to free from the interference of endogenous insulin, and the range of blood glucose levels should be consistently maintained at -10% to 0 in the euglycemic clamp.

Similar pharmacokinetics and pharmacodynamics of a new biosimilar and reference insulin aspart in healthy Chinese males

Insulin aspart (IAsp) is one of the main therapies used to control blood glucose after a meal. This study aimed to compare the pharmacokinetics (PK) and pharmacodynamics (PD) of 2 rapid-acting IAsp products: a new IAsp biosimilar (RD10046) and NovoRapid. In a single-center, randomized, single-dose, 2-period, crossover, euglycemic clamp study (registry number: CTR20180517, registration date: 2018-05-30), healthy Chinese males were randomized to receive 0.2 U/kg of the IAsp biosimilar RD10046 and NovoRapid under fasted conditions on two separate occasions. PK and PD were assessed for up to 10 h. Of the 30 randomized subjects, all 30 completed both treatment periods. The PK (area under the curve [AUC] of total IAsp; maximum observed IAsp concentration [Cmax]) and PD (maximum glucose infusion rate [GIRmax]; total glucose infusion during the clamp [AUCGIR,0-10h]) were similar between the new IAsp biosimilar RD10046 and NovoRapid. In all cases, the 90% CIs for the ratios of the geometric means were completely contained in the prespecified acceptance limits of 0.80-1.25. No hypoglycemic events, allergic reactions, or local injection adverse reactions occurred in this trial. We concluded that the studied IAsp biosimilar (RD10046) was bioequivalent to NovoRapid.

Pharmacodynamics and pharmacokinetics of a new type of recombinant insulin Lisargine injection

Background

Recombinant insulin Lisargine is a new type of insulin. In this study, we aimed to compare its pharmacodynamic (PD) and pharmacokinetic (PK) with Lantus.

Methods

The PD test was performed by exploring the effect of single administration on blood glucose of normal rats and STZ-induced diabetic rats, and the effect of multiple administrations on blood glucose of STZ-induced diabetic rats. Further PD tests include receptor affinity test, receptor autophosphorylation test and adipocyte glucose uptake test. Four IU and 8 IU per dog Lisargine was used for PK test, insulin was measured and area under curve (AUC) was calculated.

Results

With single injection, Lisargine 1.5 IU/kg had significant hypoglycemic effects at 1 and 2 h, similar to that of Lantus. Lisargine 5 IU/kg and 10 IU/kg lowered the blood glucose of STZ-induced diabetic rats at 1, 2, 4 & 6 h significantly. With multiple injections, Lantus lowered blood glucose at 2, 4 & 6 h, Lisargine 2.5 IU/kg, 5 IU/kg, and 10 IU/kg lowered blood glucose at 2 & 4 h significantly, compared with vehicle. There was no difference for receptor affinity test, receptor autophosphorylation test and adipocyte glucose uptake test between Lisargine and Lantus. The PK of Lisargine and Lantus of healthy Beagle dogs was very similar.

Conclusions

This animal study demonstrated that PK and PD of Lisargine and Lantus were similar, suggesting the bioequivalence of these products.

Oscillations of C-peptide in the euglycemic clamp and their effect on the pharmacodynamic assessment of insulin preparations

C-peptide should be continuously suppressed. However, increased postdosing C-peptide is not an uncommon phenomenon in euglycemic clamp studies involving healthy participants. This study aimed to determine the extent to which the postdosing C-peptide increases from the baseline that could affect the accuracy of glucodynamics in euglycemic clamp studies involving healthy subjects. First, 10 healthy males underwent a 10-h euglycemic clamp without exogenous insulin administration to obtain a reference interval (RI) for the ratio of C-peptide after 0 min (CP_t ) to baseline C-peptide (CP₀ ). Then, the data from a pharmacokinetic and pharmacodynamic study of insulin aspart (IAsp) were analyzed, and 70 eligible clamps were grouped by CP_t /CP₀ : group A ([CP_t /CP₀ ]_max   > upper limit of RI), group B (1<[CP_t /CP₀ ]_max  ≤ upper limit of RI), and group C ([CP_t /CP₀ ]_max  ≤ 1). The differences in basal and clamped blood glucose, CP_t /CP₀ , and the pharmacokinetics and pharmacodynamics of IAsp were compared, and the relationship between elevated CP_t and the accuracy of pharmacodynamics was analyzed. The RI of CP_t /CP₀ was 22.7%-152.1%; 1.5 × baseline might be a ceiling for the increase in CP_t under stable conditions. The maximum glucose infusion rate (GIR) in group A tended to be higher than that in group B or C (P_{for trend}  = 0.033). The AUC_GIR,0-10h in groups A, B, and C was 1983 ± 650,1682 ± 454, and 1479 ± 440 mg/kg (P = 0.047), respectively, under comparable IAsp exposure. No intergroup difference was detected in clamped glucose, IAsp dose, or body mass index. In conclusion, postdosing C-peptide over 1.5× baseline indicates insufficient inhibition of endogenous insulin secretion, which could compromise the pharmacodynamics of insulin preparations.