Kenneth Mace

Effect of renal impairment on the pharmacokinetics of exenatide.

What is already known about this subject Nonclinical studies have shown that exenatide is primarily cleared by the renal system. It was not known to what degree the clinical pharmacokinetics and tolerability would be affected by increasing renal impairment (RI). What this study adds Patients with mild to moderate RI adequately tolerate current therapeutic doses of exenatide. However, exenatide is not recommended in patients with severe RI or end-stage renal disease. Aims To evaluate the pharmacokinetics (PK), safety and tolerability of a single exenatide dose in patients with renal impairment (RI). Methods Exenatide (5 or 10 µg) was injected subcutaneously in 31 subjects (one with Type 2 diabetes) stratified by renal function [Cockcroft–Gault creatinine clearance (CrCL), number of subjects]: normal (>80 ml min−1, n = 8), mild RI (51–80 ml min−1, n = 8), moderate RI (31–50 ml min−1, n = 7) or end-stage renal disease (ESRD) requiring haemodialysis (n = 8). PK data were combined with four previous single-dose studies in patients with Type 2 diabetes to explore the relationship of exenatide clearance (CLp/F) and CrCL. Results Mean half-life for healthy, mild RI, moderate RI and ESRD groups were 1.5, 2.1, 3.2 and 6.0 h, respectively. After combining data from multiple studies, least squares geometric means for CLp/F in subjects with normal renal function, mild RI, moderate RI and ESRD were 8.14, 5.19, 7.11 and 1.3 l h−1, respectively. Exenatide was generally well tolerated in the mild and moderate RI groups, but not in subjects with ESRD due to nausea and vomiting. Simulations of exenatide plasma concentrations also suggest patients with ESRD should have a propensity for poor tolerability at the lowest available therapeutic dosage (5 µg q.d.). Conclusions Since tolerability and PK changes were considered clinically acceptable in patients with mild to moderate RI, it would be appropriate to administer exenatide to these patients without dosage adjustment. However, poor tolerability and significant changes in PK make the currently available therapeutic doses (5 and 10 µg) unsuitable in severe RI or ESRD.

Effect of exenatide on gastric emptying and relationship to postprandial glycemia in type 2 diabetes

OBJECTIVES To evaluate the effect of exenatide on gastric emptying (GE) in type 2 diabetes using scintigraphy. METHODS Seventeen subjects with type 2 diabetes participated in a randomized, single-blind, 3-period, crossover study. In each 5-day period, 5 or 10 microg exenatide or placebo was administered subcutaneously BID. Oral antidiabetic treatments were continued. The presence of cardiac autonomic neuropathy was assessed during screening. On day 5, after the morning dose, subjects consumed a 450-kcal breakfast containing (99m)Tc-labeled eggs and (111)In-labeled water, and GE was measured by scintigraphy. Plasma glucose and insulin, perceptions of appetite, and plasma exenatide were also quantified. RESULTS Exenatide slowed GE of both solid and liquid meal components [solid (T(50)(90% confidence interval [CI]); placebo, 60(50-70) min; 5 microg exenatide, 111(94-132) min; 10 microg exenatide, 169(143-201) min; both P<0.01); liquid (T(50)(90% CI), placebo, 34(25-46) min; 5 microg exenatide, 87(65-117) min; 10 microg exenatide, 114(85-154) min; both P<0.01)]. GE was not different between subjects with cardiac autonomic neuropathy (n=7), compared with those without (n=10) (P>/=0.68). Exenatide reduced postprandial glucose (area under the curve [AUC((0-6 h))]) by 69-76% and peak insulin (C(max)) by 84-86% compared with placebo. There was an inverse relationship between the postprandial rise in glucose (AUC((0-3 h))) and GE (solid T(50), r=-0.49, P<0.001). CONCLUSIONS Exenatide slows GE substantially in type 2 diabetes, which could be an important mechanism contributing to the beneficial effect of exenatide on postprandial glycemia.

Pharmacokinetics and pharmacodynamics of exenatide extended-release after single and multiple dosing.

Background and ObjectivesExenatide is a glucagon-like peptide-1 receptor agonist, available in an immediate-release (IR), twice-daily formulation, which improves glycaemic control through enhancement of glucose-dependent insulin secretion, suppression of inappropriately elevated postprandial glucagon secretion, slowing of gastric emptying and reduction of food intake. The objectives of these studies were to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of an extended-release (ER) exenatide formulation in patients with type 2 diabetes mellitus.Patients and MethodsPatients with type 2 diabetes participated in either a single-dose trial (n=62) or a repeated-administration trial (n = 45). The pharmacokinetic and safety effects of single-dose subcutaneous administration of exenatide ER (2.5 mg, 5 mg, 7 mg or 10 mg) versus placebo were studied over a period of 12 weeks in patients with type 2 diabetes. These results were used to predict the dose regimen of exenatide ER required to achieve steady-state therapeutic plasma exenatide concentrations. A second clinical study investigated the pharmacokinetics, pharmacodynamics and safety of weekly exenatide ER subcutaneous injections (0.8 mg or 2 mg) versus placebo in patients with type 2 diabetes over a period of 15 weeks. Furthermore, population-based analyses of these studies were performed to further define the exposure-response relationships associated with exenatide ER.ResultsExenatide exposure increased with dose (2.5 mg, 5 mg, 7 mg or 10 mg) and exhibited a multiple-peak profile over approximately 10 weeks. Multiple-dosing pharmacokinetics were predicted from superpositioning of single-dose data; weekly administration of exenatide ER 0.8 mg and 2 mg for 15 weeks confirmed the predictions. Weekly dosing resulted in steady-state plasma exenatide concentrations after 6–7 weeks. Fasting plasma glucose levels were reduced similarly with both doses after 15 weeks (−42.7 ±15.7 mg/dL with the 0.8mg dose and −39.0±9.3mg/dL with the 2mg dose; both p<0.001 vs placebo), and the integrated exposure-response analysis demonstrated that the drug concentration producing 50% of the maximum effect (EC50) on fasting plasma glucose was 56.8 pg/mL (a concentration achieved with both the 0.8 mg and 2mg doses of exenatide ER). The 2 mg dose reduced bodyweight (−3.8 ± 1.4kg; p<0.05 vs placebo) and postprandial glucose excursions. Glycosylated haemoglobin (HbAlc) levels were reduced with the 0.8 mg dose (−1.4±0.3%; baseline 8.6%) and with the 2mg dose (−1.7 ± 0.3%; baseline 8.3%) [both p<0.001 vs placebo]. Adverse events were generally transient and mild to moderate in intensity.ConclusionThese studies demonstrated that (i) a single subcutaneous dose of exenatide ER resulted in dose-related increases in plasma exenatide concentrations; (ii) single-dose exposure successfully predicted the weekly-dosing exposure, with 0.8 mg and 2 mg weekly subcutaneous doses of exenatide ER eliciting therapeutic concentrations of exenatide; and (iii) weekly dosing with either 0.8 or 2 mg of exenatide ER improved fasting plasma glucose control, whereas only the 2 mg dose was associated with improved postprandial glucose control and weight loss.[Clinicaltrials.gov Identifier: NCT00103935]

Pharmacokinetics and Pharmacodynamics of High-Dose Human Regular U-500 Insulin Versus Human Regular U-100 Insulin in Healthy Obese Subjects

OBJECTIVE Human regular U-500 (U-500R) insulin (500 units/mL) is increasingly being used clinically, yet its pharmacokinetics (PK) and pharmacodynamics (PD) have not been well studied. Therefore, we compared PK and PD of clinically relevant doses of U-500R with the same doses of human regular U-100 (U-100R) insulin (100 units/mL). RESEARCH DESIGN AND METHODS This was a single-site, randomized, double-blind, crossover euglycemic clamp study. Single subcutaneous injections of 50- and 100-unit doses of U-500R and U-100R were administered to 24 healthy obese subjects. RESULTS Both overall insulin exposure (area under the serum insulin concentration versus time curve from zero to return to baseline [AUC0-t’]) and overall effect (total glucose infused during a clamp) were similar between formulations at both 50- and 100-unit doses (90% [CI] of ratios contained within [0.80, 1.25]). However, peak concentration and effect were significantly lower for U-500R at both doses (P < 0.05). Both formulations produced relatively long durations of action (18.3 to 21.5 h). Time-to-peak concentration and time to maximum effect were significantly longer for U-500R than U-100R at the 100-unit dose (P < 0.05). Time variables reflective of duration of action (late tRmax50, tRlast) were prolonged for U-500R versus U-100R at both doses (P < 0.05). CONCLUSIONS Overall exposure to and action of U-500R insulin after subcutaneous injection were no different from those of U-100R insulin. For U-500R, peaks of concentration and action profiles were blunted and the effect after the peak was prolonged. These findings may help guide therapy with U-500R insulin for highly insulin-resistant patients with diabetes.

Discovery and development of exenatide: the first antidiabetic agent to leverage the multiple benefits of the incretin hormone, GLP-1.

Introduction: The GLP-1 receptor agonist exenatide is synthetic exendin-4, a peptide originally isolated from the salivary secretions of the Gila monster. Exenatide was developed as a first-in-class diabetes therapy, with immediate- and extended-release formulations. In preclinical diabetes models, exenatide enhanced glucose-dependent insulin secretion, suppressed inappropriately elevated glucagon secretion, slowed gastric emptying, reduced body weight, enhanced satiety, and preserved pancreatic β-cell function. In clinical trials, both exenatide formulations reduced hyperglycemia in patients with type 2 diabetes mellitus (T2DM) and were associated with weight loss. Areas covered: This article reviews the development of exenatide from its discovery and preclinical investigations, to the elucidation of its pharmacological mechanisms of action in mammalian systems. The article also presents the pharmacokinetic profiling and toxicology studies of exenatide, as well as its validation in clinical trials. Expert opinion: GLP-1 receptor agonists represent a new paradigm for the treatment of patients with T2DM. By leveraging incretin physiology, a natural regulatory system that coordinates oral nutrient intake with mechanisms of metabolic control, these agents address multiple core defects in the pathophysiology of T2DM. Studies have identified unique benefits including improvements in glycemic control and weight, and the potential for beneficial effects on the cardiometabolic system without the increased risk of hypoglycemia associated with insulin therapy. Peptide hormone therapeutics can offer significant advantages over small molecule drug targets when it comes to specificity, potency, and more predictable side effects. As exemplified by exenatide, injectable peptides can be important drugs for the treatment of chronic diseases, such as T2DM.

Steady-state pharmacokinetics and glucodynamics of the novel, long-acting basal insulin LY2605541 dosed once-daily in patients with type 2 diabetes mellitus.

To assess the pharmacokinetics (PK) and glucodynamics (GD) of LY2605541 in patients with type 2 diabetes mellitus.

Effect of exenatide on the steady-state pharmacokinetics of digoxin.

This open‐label study investigated the effect of exenatide coadministration on the steady‐state plasma pharmacokinetics of digoxin. A total of 21 healthy male subjects received digoxin (day 1, 0.5 mg twice daily; days 2–12, 0.25 mg once daily) and exenatide (days 8–12, 10 μg twice daily). Digoxin plasma and urine concentrations were measured on days 7 and 12. Exenatide coadministration did not change the overall 24‐hour steady‐state digoxin exposure (AUCτ,ss) and Cmin,ss but caused a 17% decrease in mean plasma digoxin Cmax,ss (1.40 to 1.16 ng/mL) and an increase in digoxin tmax,ss (median increase, 2.5 hours). Although the decrease in digoxin Cmax,ss was statistically significant, peak concentrations were within the therapeutic concentration range in all subjects. Digoxin urinary pharmacokinetic parameters were not altered. Gastrointestinal symptoms, the most common adverse effects of exenatide, decreased over time. Exenatide administration does not cause any changes in digoxin steady‐state pharmacokinetics that would be expected to have clinical sequelae; thus, dosage adjustment does not appear warranted, based on pharmacokinetic considerations.

Pharmacokinetics, Pharmacodynamics, Tolerability, and Safety of Exenatide in Japanese Patients With Type 2 Diabetes Mellitus

In this single‐blind, parallel, placebo‐controlled study, the pharmacokinetics, pharmacodynamics, tolerability, and safety of subcutaneous exenatide were evaluated in 40 Japanese patients with type 2 diabetes. Patients were allocated to 4 groups and randomized to receive exenatide (n = 8/group) or placebo (n = 2/group), with all receiving placebo on day 1. On day 2, patients received single‐dose exenatide (2.5 μg [group A] or 5 μg [groups B, C, and D]) or placebo and then bid on days 3 to 5. On days 6 to 10, groups A and B continued on 2.5 and 5 μg bid; groups C and D received 10 and 15 μg bid, respectively. The last dose was given on the morning of day 10. All adverse events were mild or moderate in severity. Exenatide was generally well tolerated up to 10 μg. Exenatide was well absorbed with a median tmax of 1.5 hours and mean t1/2 of 1.6 hours; exposure increased with dose. Up to 10 μg, exenatide reduced postprandial glucose concentrations in a dose‐dependent fashion compared with placebo; decreases were similar for 10 and 15 μg. An Emax model demonstrated that doses higher than 2.5 μg were necessary for adequate glycemic response. Based on tolerability and pharmacokinetic/pharmacodynamic relationships, 5 and 10 μg exenatide may be considered for further clinical development in Japanese patients with type 2 diabetes.

Effect of exenatide on the pharmacokinetics and pharmacodynamics of warfarin in healthy Asian men

Exenatide, a treatment for type 2 diabetes, slows gastric emptying as part of its pharmacologic action and may alter the absorption of concomitant oral drugs. This open‐label, 2‐period, fixed‐sequence study evaluated the influence of exenatide coadministration on the pharmacokinetics and pharmacodynamics of warfarin, a narrow therapeutic index drug, in healthy men (N = 16). A single, 25‐mg oral dose of warfarin, with a standardized breakfast, was administered alone in period 1 and concomitantly with 10 μg exenatide subcutaneous twice daily in period 2. Exenatide did not produce significant changes in R‐ or S‐warfarin pharmacokinetics. Although there were minor reductions in warfarin anticoagulant effect, the ratios of geometric means for the area under the international normalized ratio (INR)–time curve from dosing until the time of the last measurable INR value or maximum‐observed INR response being 0.94 (0.93‐0.96) and 0.88 (0.84‐0.92), respectively, the magnitude and direction of these changes do not suggest a safety concern from this interaction.

Single-dose pharmacokinetics and glucodynamics of the novel, long-acting basal insulin LY2605541 in healthy subjects.

LY2605541 is a novel basal insulin analog with a prolonged duration of action. Two Phase I studies assessed LY2605541 pharmacokinetics (PK), glucodynamics (GD), and tolerability in healthy subjects. In Study 1, 33 subjects received single subcutaneous (SC) doses of LY2605541 (0.01–2.22 U/kg) and insulin glargine (0.5–0.8 U/kg) followed by euglycemic clamp for up to 24–36 hours. In Study 2, absolute bioavailability of SC LY2605541 was assessed in 8 subjects by comparing dose normalized area under concentration versus time curve of SC against IV administration. Time‐to‐maximum plasma concentration (medians) and geometric means for half‐life (t1/2) and apparent clearance, respectively, ranged from 18.0 to 42.0 hours, 24.4–45.5 hours, and 1.8–2.8 L/h for SC LY2605541, versus 10.0–12.0 hours, 12.2–14.9 hours, and 51.4–65.2 L/h for SC insulin glargine. LY2605541 glucose infusion rate (GIR) profiles were sustained for ≥36 hours versus glargine GIR profiles, which waned at 24 hours. After IV administration, LY2605541s geometric mean t1/2 was 2.3 hours. LY2605541 intra‐subject variability (CV%) was <18% for PK and <32% for GD parameters. The most common adverse events were related to study procedures and were mild‐moderate in severity. These results established a well‐tolerated baseline dose for LY2605541 with a relatively flat PK profile and low intra‐subject variability.