Pharmacokinetics of the Long-Acting Basal Insulin LY2605541 in Subjects With Varying Degrees of Renal Function

The pharmacokinetics of LY2605541 (basal insulin peglispro), a novel long-acting basal insulin analogue, was evaluated in 5 groups of subjects with varying degrees of renal function based on creatinine clearance: normal renal function (>80 mL/min), mild renal impairment (51-80 mL/min), moderate renal impairment (30-50 mL/min), severe renal impairment (<30 mL/min), or end-stage renal disease (ESRD) requiring hemodialysis. Serial blood samples for pharmacokinetic analyses were collected up to 12 days following a single 0.33 U/kg subcutaneous dose of LY2605541. The apparent clearance (CL/F) and half-life across groups were not affected by renal function. Cmax values were lower in subjects with increasing severity of renal impairment; however, the small decrease in Cmax did not affect the overall exposure. Regression analysis showed that LY2605541 clearance is independent of renal function (slope = 0.000863; P = .885). The mean fraction of LY2605541 eliminated by a single hemodialysis session was 13% in subjects with ESRD. LY2605541 was generally well tolerated in healthy subjects and those with renal impairment following a single 0.33 U/kg subcutaneous dose. Given these data, no dose adjustment of LY2605541 based on pharmacokinetics is recommended in renal impairment or in patients undergoing hemodialysis.

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

AIMS

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

METHODS

This parallel-group, open-label, dose-escalation study examined the PK and GD of basal insulin LY2605541 after single and multiple-dose administration. Fixed doses of LY2605541 (0.33-1.00 U/kg) were given once-daily (QD) for 14 days to insulin-treated patients with type 2 diabetes. A 24-h euglycaemic glucose clamp was conducted on days 1 and 14.

RESULTS

PK steady state was achieved within 7-10 days and the peak-to-trough fluctuation was <2, translating to a nearly 'peakless' glucose infusion rate at steady state and with a duration of action of at least 24 h. Across dose levels t1/2 ranged from 44.7 to 75.5 h (~2-3 days). As steady state was achieved, there were dose-dependent reductions in the prandial insulin dose and in fasting blood glucose, which decreased to 60-100 mg/dl across dose levels. Within-patient variability was <14 and <26% for the area under the concentration versus time curve (AUC) of the 8-point blood glucose profile and fasting blood glucose, respectively. The nocturnal glucose control between 03:00 and 09:00 hours was relatively unchanged. Mild hypoglycaemia was the most common adverse event.

CONCLUSIONS

In this Phase I study of fixed LY2605541 doses without titration, LY2605541 was well-tolerated and demonstrated a flat PK and GD profile accompanied by glucose normalization, prandial insulin dose reduction and no severe hypoglycaemia.

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 (t½ ) 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, LY2605541's geometric mean t½ 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.

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 microg 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 (AUCtau,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.

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.

Clinical relevance of anti-exenatide antibodies: safety, efficacy and cross-reactivity with long-term treatment

AIMS

Antibody formation to therapeutic peptides is common. This analysis characterizes the time-course and cross-reactivity of anti-exenatide antibodies and potential effects on efficacy and safety.

METHODS

Data from intent-to-treat patients in 12 controlled (n = 2225,12-52 weeks) and 5 uncontrolled (n = 1538, up to 3 years) exenatide twice-daily (BID) trials and 4 controlled (n = 653,24-30 weeks) exenatide once weekly (QW) trials with 1 uncontrolled period (n = 128,52 weeks) were analysed.

RESULTS

Mean titres peaked early (6-22 weeks) and subsequently declined. At 30 weeks, 36.7% of exenatide BID patients were antibody-positive; 31.7% exhibited low titres (≤125) and 5.0% had higher titres (≥625). Antibody incidence declined to 16.9% (1.4% higher titre) at 3 years. Similarly, 56.8% of exenatide QW patients were antibody-positive (45.0% low/11.8% higher titre) at 24-30 weeks, declining to 45.4% positive (9.2% higher titre) at 52 weeks. Treatment-emergent anti-exenatide antibodies from a subset of patients tested did not cross-react with human GLP-1 or glucagon. Other than injection-site reactions, adverse event rates in antibody-positive and antibody-negative patients were similar. Efficacy was robust in both antibody-negative and antibody-positive patients (mean HbA1c change: -1.0 and -0.9%, respectively, exenatide BID; -1.6% and -1.3% exenatide QW). No correlation between change in HbA1c and titre was observed for exenatide BID, although mean reductions were attenuated in the small subset of patients (5%) with higher titres. A significant correlation was observed for exenatide QW with no difference between antibody-negative and low-titre patients, but an attenuated mean reduction in the subset of patients (12%) with higher titres.

CONCLUSIONS

Low-titre anti-exenatide antibodies were common with exenatide treatment (32% exenatide BID, 45% exenatide QW patients), but had no apparent effect on efficacy. Higher-titre antibodies were less common (5% exenatide BID, 12% exenatide QW) and within that titre group, increasing antibody titre was associated with reduced average efficacy that was statistically significant for exenatide QW. Other than injection-site reactions, anti-exenatide antibodies did not impact the safety of exenatide.

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 [AUC(0-)(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 tR(max50), tR(last)) 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.

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 microg 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.

Differential inhibition of platelet aggregation induced by adenosine diphosphate or a thrombin receptor-activating peptide in patients treated with bolus chimeric 7E3 Fab: implications for inhibition of the internal pool of GPIIb/IIIa receptors

OBJECTIVES

This study sought to describe in detail the pharmacokinetics and pharmacodynamics of chimeric monoclonal 7E3 Fab (c7E3 Fab) and to compare platelet responses to adenosine diphosphate (ADP) and the 11-amino acid thrombin receptor-activating peptide (TRAP [SFLLRNPNDKY-NH2]) in patients undergoing elective coronary angioplasty.

BACKGROUND

Inhibition of platelet aggregation with monoclonal antibody c7E3 Fab directed against glycoprotein (GP) IIb/IIIa has been shown to reduce ischemic complications after angioplasty and is being considered for treatment of other acute ischemic syndromes.

METHODS

Patients undergoing elective coronary angioplasty received aspirin (325 mg orally), heparin (12,000 U intravenously) and a bolus of c7E3 Fab (0.25 mg/kg body weight). Surface GPIIb/IIIa receptor blockade and aggregation in response to 20 mumol/liter ADP, 5 micrograms/ml collagen and 7.5 and 15 mumol/liter TRAP were assessed.

RESULTS

Surface GPIIb/IIIa receptor blockade by c7E3 Fab was 80% 2 h after injection and decreased to 50% at 24 h. Platelet aggregation in response to 20 mumol/liter ADP was inhibited by 73% at 2 h, and this inhibition decreased to 27% at 24 h. Platelet aggregation in response to 7.5 mumol/liter TRAP was inhibited by 53% at 2 h and 30% at 24 h. In contrast, aggregation in response to 15 mumol/liter TRAP was inhibited only 37% at 2 h and 10% at 24 h (p < 0.001 and p = 0.006, respectively vs. 20 mumol/liter ADP). Addition of exogenous c7E3 Fab to platelet-rich plasma led to more complete inhibition of 7.5 mumol/liter TRAP-induced aggregation.

CONCLUSIONS

After c7E3 Fab treatment, inhibition of platelet aggregation depends on the agonist and can be overcome by increased thrombin activity but is restored if additional c7E3 Fab is added to block additional GPIIb/IIIa receptors. This phenomenon may be related to an internal pool of GPIIb/IIIa receptors joining the surface membrane and has implications concerning the duration of therapy with c7E3 Fab for patients with unstable angina or acute myocardial infarction.

Adriamycin-induced modulation of host defenses in tumor-bearing mice

Using the C57BL/6/EL4 tumor model, studies were carried out to demonstrate the feasibility of administering Adriamycin (ADM) in therapeutic doses and schedules such that the host antitumor defenses would not be suppressed and in some cases might be stimulated by treatment. ADM treatment caused prolongation of survival and, in general, either stimulated host cytolytic activities above untreated control levels or had no effect. These effects by ADM were observed with the ADM-sensitive parent EL4 line as well as with an ADM-resistant subline, indicating that the effects did not result entirely from direct antitumor activity. The cytolytic activities examined were those of cytolytic T-lymphocytes, lymphokine-activated killer cells, and splenic and peritoneal macrophages. All activities were assessed against the syngeneic EL4 target line. The information obtained in this investigation provides a rational basis for the future development of curative protocols with ADM plus biological response modifiers, which would depend on a functional immune system for optimum efficacy and would also exploit synergistic immunomodulating effects of the agents used in combination.

Correlation between in vivo induction of cytokine gene expression by flavone acetic acid and strict dose dependency and therapeutic efficacy against murine renal cancer

The investigational chemotherapeutic drug flavone acetic acid (FAA) acts as an immunomodulator by augmenting natural killer activity in both humans and rodents after in vivo administration. The accumulated data derived from a series of experiments also demonstrates that FAA synergizes with interleukin 2 (IL-2) for the treatment of murine renal cancer. The immunomodulatory and immunotherapeutic effects of FAA are strictly dose dependent with doses of FAA greater than 150 mg/kg effectively synergizing with IL-2, and doses less than 150 mg/kg exhibiting very little therapeutic effect. The antitumor and immunomodulatory effects of FAA are more pronounced in vivo than in vitro. Collectively, these results suggested that cytokines induced by FAA may contribute to these effects, and that the induction of such cytokines may also be very dose dependent. Studies were therefore initiated to investigate whether the in vivo administration of FAA would alter the expression of cytokine mRNA in leukocytes. Splenic leukocytes or liver nonparenchymal cells from untreated and FAA-treated mice were used as a source of RNA for Northern blot analysis. Interferon alpha and interferon gamma mRNA in the spleen was upregulated within 1.5 h after FAA administration, with peak induction occurring by about 2 h. An upregulation of tumor necrosis factor alpha mRNA was detected in the spleen by 0.5-1 h after treatment with peak induction occurring by 1-1.5 h. Induction of tumor necrosis factor alpha mRNA was also detected in hepatic nonparenchymal cells. No up-regulation of splenic mRNA for tumor necrosis factor beta, IL-1 alpha or beta, or IL-2 was detected after FAA administration. IFN and TNF activities were detectable in the serum by bioassay immediately following the appearance of mRNA in FAA mice. The observed up-regulation by FAA of cytokine mRNA and the corresponding serum protein was strictly dose dependent with substantial induction of both mRNA and proteins occurring only at FAA doses greater than or equal to 150 mg/kg, a dose range also shown to be the minimum required for immunomodulatory and immunotherapeutic effects. In summary, these results demonstrate that FAA acts as a potent inducer of at least three cytokines in vivo, and suggest that the immunomodulatory and immunotherapeutic effects of FAA may be partially mediated by these induced cytokines.

Modification of host antitumor defense mechanisms in mice by progressively growing tumor

The EL4 lymphoma in C57BL/6 mice was used as a model to examine the effect of progressive tumor growth on a variety of cell mediated cytolytic effector functions which have been shown in other systems to have antitumor potential. The functions examined were those of cytolytic T-lymphocyte, lymphokine activated killer cells, natural killer cells, and tumoricidal macrophage (MO). The kinetics of each function displayed a unique pattern as a consequence of tumor growth, but all were inhibited in animals bearing large tumors (late tumor bearers). In cell mixing experiments it was shown that spleen cells from individual late tumor bearers were suppressive for cytotoxic T-lymphocytes, lymphokine activated killer cells, and splenic MO but not peritoneal MO or splenic natural killer cells. The suppression was nonspecific and was mediated primarily by nonadherent cells and/or their soluble products. Suppression appeared to be mediated, in part, by tumor cells in the spleen since the degree of suppressor activity associated with a particular spleen cell preparation correlated with the number of tumor cells present. Furthermore, the direct addition of viable ascites EL4 cells to response cultures or assays had similar suppressive effects as late TBM spleen cells, i.e., inhibited cytotoxic T-lymphocytes, lymphokine activated killer cells, and splenic MO but had no effect on natural killer cells or peritoneal MO. The mechanism of suppression by ascites EL4 was not determined but it was mediated by viable cells only and not due to contaminating viruses or other microorganisms.

Role of tumor necrosis factor in macrophage activation and tumoricidal activity

Tumor necrosis factor (TNF)-sensitive (LM) and -insensitive (P815) target cell lines were used to examine the role of TNF in both the activation and lytic phases of macrophage-mediated lysis. LM cells were lysed spontaneously by thioglycolate-elicited macrophages in an 18-h assay (media or activating agents added with targets) or 36-h assay (macrophages cultured with media or activating agents for 18 h, washed, and targets added for a subsequent 18 h). In contrast, P815 cells were lysed only in the 36-h assay by macrophages exposed to appropriate activation signals. Using antibody to murine TNF, it was shown that lysis of LM cells but not P815 cells was TNF mediated. The addition of lipopolysaccharide (LPS) to the 18-h assay resulted in augmented LM killing. This was probably due to the fact that LPS stimulates macrophages to produce TNF. Conversely, when macrophages were pretreated with LPS for 18 h, washed, and assessed for lytic activity during the subsequent 18 h, lysis of LM cells was reduced relative to the endogenous level. Although macrophage lysis of P815 was not mediated by TNF, the addition of TNF to macrophage activation cultures facilitated LPS triggering of cytolytic activity against P815. Similarly, the addition of TNF to the activation cultures partially prevented the LPS-induced reduction in macrophage-mediated LM cell lysis. Taken together, these data suggest that TNF may act as an autocrine signal during macrophage activation, in addition to being directly lytic to a select number of sensitive target cell lines.

Comparison of adriamycin induced immunomodulation with that of the noncardiotoxic anthracycline 5-iminodaunorubicin

Adriamycin (ADM) has been shown to modulate a variety of host immune responses. Although the mechanism(s) for this activity is not known, it has been suggested that free radical compounds generated during ADM metabolism act at the membrane level to alter immune cell function. The generation of free radical metabolites is also believed to be responsible for the cardiotoxic potential of ADM. 5-Iminodaunorubicin (IDM) is a non-cardiotoxic anthracycline analog which undergoes minimal free radical metabolism. In the present study the immunomodulatory capacity of IDM was compared to that of ADM. It was found that IDM and ADM had similar augmenting effects on cytolytic T-cell activity and that this correlated with: (1) Fc-dependent phagocytosis by spleen cells; and (2) the elimination or inhibition of an adherent regulatory cell in the spleen. The natural killer response was either unaffected (fresh NK) or slightly inhibited (cultured NK) by both drugs except moderate dose IDM which resulted in marked augmentation of cultured NK.