0198 Psychomotor/Cognitive Effects, Pharmacokinetics and Safety of V117957, a Novel, Highly Potent and Selective Partial Agonist for Nociceptin/Orphanin-FQ Peptide (NOP) Receptors, Administered in Combination with Alcohol in Healthy Subjects

Introduction

V117957 is an investigational nociceptin/orphanin-FQ peptide (NOP) receptor partial agonist designed to treat insomnia by promoting sleep onset and maintenance with minimal residual next-day somnolence or psychomotor impairment. The satisfactory safety/tolerability profile of V117957 has been previously established in ~200 healthy subjects with maximum doses at 30mg following a single oral administration and 10mg once daily for 2 weeks. The present study was conducted to assess the safety/tolerability and pharmacokinetics (PK) of V117957 with co-administered alcohol.

Methods

A randomized, double-blind, double-dummy, placebo-controlled, balanced six-period crossover design was employed. Single doses (2mg, 6mg) of V117957 and placebo were administered orally to healthy subjects in the morning with and without alcohol (0.7g/kg). Pharmacodynamic (PD) effects of V117957 were assessed, and safety/tolerability and PK interactions were also characterized. The primary PD endpoints (body sway, Digit Vigilance Test, and numeric working memory) were measured through 12 hours postdosing.

Results

Forty-eight subjects were enrolled and randomized; 46 completed. Compared with placebo, alcohol alone showed an impairment on psychomotor/cognitive performances through 2 hours postdose. V117957 alone showed a dose-dependent impairment. Compared with V117957 alone and alcohol alone, co-administration of alcohol and V117957 showed greater impairment until 8 hours postdose. No subject discontinued due to an adverse event (AE). No clinically meaningful treatment-emergent (TE) changes in clinical laboratory values, vital signs, SpO2 measurements, or 12-lead ECG results were observed. The most common TEAE was somnolence. All plasma and urine PK parameters for V117957 and alcohol were comparable when V117957 or alcohol was administered alone or in combination.

Conclusion

Single oral doses of V117957, 2mg or 6mg, administered alone or in combination with alcohol in healthy subjects resulted in no notable PK interaction between V117957 and alcohol. A dose-effect relationship in the magnitude and duration of impairment was observed for most psychomotor/cognitive performance parameters. Greater effects of V117957 with alcohol were observed for most psychomotor/cognitive performance parameters up to 8 hours post-dose.

Support

Funded by Imbrium Therapeutics, a subsidiary of Purdue Pharma L.P.

0500 Evaluation of the Human Abuse Potential of Single Oral Doses of V117957, a Novel, Highly Potent and Selective Partial Agonist for Nociceptin/Orphanin-FQ Peptide (NOP) Receptors

Introduction

The satisfactory safety/tolerability profile of V117957, an investigational NOP receptor partial agonist, has been previously established in ~200 healthy subjects with maximum doses at 30mg following a single oral administration and 10mg once daily for 2 weeks. V117957 exhibited linear plasma exposures at doses up to 10mg. In patients with insomnia disorder, V117957 demonstrated dose-dependent improvement in sleep efficiency and sleep maintenance between 0.5mg and 10mg as measured by polysomnography and patient diaries. The current study evaluated the abuse potential and safety of V117957 in healthy, nondependent recreational polydrug users with a history of central nervous system (CNS) depressant use.

Methods

The abuse potential of V117957 (1mg, 6mg, 10mg), placebo, and triazolam (0.5mg, 1mg) were assessed in a randomized, double-blind, double-dummy, placebo- and positive-controlled crossover study. Triazolam was utilized as a positive control based on its comparable pharmacokinetic and pharmacodynamic characteristics. V117957 doses (1mg, 6mg, 10mg) were selected to represent therapeutic, mid-range supratherapeutic, and maximum-tolerated supratherapeutic doses, respectively. Subjects were qualified based on pharmacodynamic responses following a single oral 0.75mg triazolam dose. Drug liking was measured through 24 hours, including the primary endpoint of maximum “at the moment” Drug-Liking Visual Analog Scale, as recommended by FDA. Secondary endpoints included Divided Attention Test (DAT) and Choice Reaction Time (CRT).

Results

The positive control (triazolam 0.5mg, 1mg) produced statistically significant greater abuse potential and cognitive/motor impairment versus placebo, which demonstrated study validity. In contrast, V117957 at 1mg was not statistically significantly different from placebo. At the supra-therapeutic doses of 6 and 10mg, V117957 was associated with abuse potential and cognitive/motor impairment greater than placebo, yet similar to those of triazolam 0.5 and 1mg.

Conclusion

Overall, in this valid study, V117957 1mg and placebo were associated with statistically significant lower potential for abuse and reduced cognitive/motor impairment compared with the two supratherapeutic doses of V117957 (6mg, 10mg), and triazolam (0.5mg, 1mg). V117957 1mg met FDA’s statistical criterion for similarity to placebo.

Support

Funded by Imbrium Therapeutics, a subsidiary of Purdue Pharma L.P.

Hyperthermia induced by transient receptor potential vanilloid-1 (TRPV1) antagonists in human clinical trials: Insights from mathematical modeling and meta-analysis

Antagonists of the transient receptor potential vanilloid-1 (TRPV1) channel alter body temperature (T_b) in laboratory animals and humans: most cause hyperthermia; some produce hypothermia; and yet others have no effect. TRPV1 can be activated by capsaicin (CAP), protons (low pH), and heat. First-generation (polymodal) TRPV1 antagonists potently block all three TRPV1 activation modes. Second-generation (mode-selective) TRPV1 antagonists potently block channel activation by CAP, but exert different effects (e.g., potentiation, no effect, or low-potency inhibition) in the proton mode, heat mode, or both. Based on our earlier studies in rats, only one mode of TRPV1 activation - by protons - is involved in thermoregulatory responses to TRPV1 antagonists. In rats, compounds that potently block, potentiate, or have no effect on proton activation cause hyperthermia, hypothermia, or no effect on T_b, respectively. A T_b response occurs when a TRPV1 antagonist blocks (in case of hyperthermia) or potentiates (hypothermia) the tonic TRPV1 activation by protons somewhere in the trunk, perhaps in muscles, and - via the acido-antithermogenic and acido-antivasoconstrictor reflexes - modulates thermogenesis and skin vasoconstriction. In this work, we used a mathematical model to analyze T_b data from human clinical trials of TRPV1 antagonists. The analysis suggests that, in humans, the hyperthermic effect depends on the antagonist's potency to block TRPV1 activation not only by protons, but also by heat, while the CAP activation mode is uninvolved. Whereas in rats TRPV1 drives thermoeffectors by mediating pH signals from the trunk, but not T_b signals, our analysis suggests that TRPV1 mediates both pH and thermal signals driving thermoregulation in humans. Hence, in humans (but not in rats), TRPV1 is likely to serve as a thermosensor of the thermoregulation system. We also conducted a meta-analysis of T_b data from human trials and found that polymodal TRPV1 antagonists (ABT-102, AZD1386, and V116517) increase T_b, whereas the mode-selective blocker NEO6860 does not. Several strategies of harnessing the thermoregulatory effects of TRPV1 antagonists in humans are discussed.

Effect of Multiple-Dose Dexloxiglumide on the Pharmacokinetics of Oral Contraceptives in Healthy Women

This study was undertaken to evaluate the effect of dexloxiglumide, a selective cholecystokinin receptor antagonist, on the pharmacokinetics of a combination oral contraceptive (OC). A single-blind, placebo-controlled, 2-period crossover study was conducted in 24 healthy young female subjects who received Ortho Tri-Cyclen containing ethinyl estradiol (EE, 0.035 mg) and norgestimate (NE, 0.180 mg/0.215 mg/0.250 mg per 7-day phase, respectively) for 5 days (days 17-21) concurrently with either 200 mg dexloxiglumide (3 times a day on days 17-20, followed by a single dose on day 21) or matching placebo during 2 consecutive 28-day OC dosing cycles. Plasma was sampled up to 24 hours for the determination of EE, NE, and 17-deactyl norgestimate (17-DNE, a rapidly formed pharmacologically active metabolite of NE). The geometric mean ratios (GMRs, dexloxiglumide/placebo) of the plasma concentration-time curve over 24 hours with corresponding 90% confidence intervals (CIs) for EE and 17-DNE were 1.21 (1.17-1.26) and 0.92 (0.89-0.95), respectively. The GMRs (90% CI) of C(max) for EE and 17-DNE were 1.15 (1.09-1.20) and 0.93 (0.90-0.96), respectively. Coadministration of OC and dexloxiglumide was well tolerated and safe. Comparable systemic exposure of EE and 17-DNE in the presence and absence of dexloxiglumide suggests that dexloxiglumide treatment is unlikely to interfere with the safety and efficacy of oral contraceptives based on the analysis of the resulting pharmacokinetic profile.

Development and validation of a spectrofluorimetric method for the estimation of rivastigmine in formulations

A rapid, sensitive, simple, and cost-effective spectrofluorimetric method was developed for the estimation of rivastigmine in bulk and pharmaceutical formulations. The relative fluorescence intensity of rivastigmine was measured in triple distilled water at an excitation wavelength of 220 nm and an emission wavelength of 289 nm. Linearity range was found to be 100 to 4000 ng/ml. The method was validated for various parameters as per the ICH guidelines and USP requirements. The detection and quantitation limits were found to be 20.5 and 62.1 ng/ml, respectively. The results demonstrate that the procedure is accurate, precise, and reproducible, while being simple and rapid too. The results were found to be in good agreement with the label claims.

Effect of azole antifungals ketoconazole and fluconazole on the pharmacokinetics of dexloxiglumide

AIMS

Dexloxiglumide is a new CCK(1) receptor antagonist under investigation for treatment of functional gastrointestinal disorders and is metabolized by CYP3A4 and CYP2C9. The objectives of these two separate randomized, two-period, two-treatment crossover studies were to investigate the effects of steady-state ketoconazole, a model CYP3A4 inhibitor (Study 1), and steady-state fluconazole, a model CYP2C9 inhibitor (Study 2), on the pharmacokinetics of dexloxiglumide in healthy subjects.

METHODS

Plasma samples were analysed for dexloxiglumide and its primary metabolites: O-demethyl dexloxiglumide (ODM; Study 1 and 2) and dexloxiglumide carboxylic acid (DCA; Study 2).

RESULTS

Following ketoconazole coadministration, dexloxiglumide C(max) increased by 32% (90% confidence intervals (CI) 112-154), with unchanged ODM C(max); AUC of dexloxiglumide and ODM increased by 36% (90% CI 124-140 and 128-142, respectively). No changes were observed in dexloxiglumide or ODM t((1/2)). Fluconazole coadministration caused a 77% increase (90% CI 154-204) in dexloxiglumide C(max), no change in ODM C(max) and a 32% decrease (90% CI 62-75) in DCA C(max). Fluconazole coadministration resulted in a 2.5-fold increase (90% CI 235-267) in dexloxiglumide AUC, 40% increase (90% CI 136-156) in ODM AUC and an 18% decrease (90% CI 82-94) in DCA AUC. The t((1/2)) of all three analytes increased by approximately 2-fold with fluconazole coadministration (P-value < 0.05).

CONCLUSIONS

Ketoconazole caused a minimal increase while fluconazole caused a moderate increase in dexloxiglumide systemic exposure with no change in the adverse event profile of dexloxiglumide.

Pharmacokinetic Profile of Dexloxiglumide

Dexloxiglumide is a potent and selective cholecystokinin type 1 (CCK1) receptor antagonist currently under development in a variety of diseases affecting the gastrointestinal tract such as gastro-oesophageal reflux disease, irritable bowel syndrome (IBS), functional dyspepsia, constipation and gastric emptying disorders. In female patients with constipation-predominant IBS, clinical efficacy has been demonstrated following administration of dexloxiglumide 200 mg three times daily. Dexloxiglumide is rapidly and extensively absorbed after single oral administration in humans with an absolute bioavailability of 48%. The incomplete bioavailability is due to both incomplete absorption and hepatic first-pass effect. Following multiple-dose administration of 200 mg three times daily, the accumulation is predictable, indicating time-independent pharmacokinetics. In addition, dexloxiglumide pharmacokinetics are dose-independent after both single and repeated oral three-times-daily doses in the dose range 100-400 mg. Dexloxiglumide absorption window extends from the jejunum to the colon and the drug is a substrate and a weak inhibitor of P-glycoprotein and multidrug resistance protein 1. Plasma protein binding of dexloxiglumide is 94-98% and the drug has a moderate to low volume of distribution in humans. Systemic clearance of dexloxiglumide is moderate and cytochrome P450 (CYP) 3A4/5 and CYP2C9 have been implicated in the metabolism of dexloxiglumide to produce O-demethyl dexloxi-glumide. This metabolite is further oxidised to dexloxiglumide carboxylic acid. These two major metabolites (accounting for up to 50% of dexloxiglumide elimination) have been identified. However, in human plasma the unchanged drug represents the major (up to 91%) component of the metabolic profile. The parent drug is believed to be the major contributor to the efficacy of the compound, since its major metabolites are pharmacologically inactive. In addition, the drug is a single isomer chiral drug (eutomer) that does not undergo chiral inversion into its pharmacologically inactive enantiomer (distomer). After oral administration of (14)C-dexloxiglumide, radioactivity is mainly excreted in bile and in faeces (74% of dose) with much lower excretion in urine (20% of dose). Renal excretion of unchanged dexloxiglumide is low (7% of dose in urine and faeces, 1% of dose in urine) and is dose-independent in the dose range 100-400 mg. As the kidney is a minor contributor to the elimination of dexloxiglumide and/or its metabolites in humans, the pharmacokinetics of the drug should not be affected in patients with renal insufficiency. The pharmacokinetics of dexloxiglumide are also not affected by age, sex and administration with a high-fat breakfast. Mild and moderate liver impairment do not affect the pharmacokinetics of dexloxiglumide but severe liver impairment causes increases in systemic exposure to dexloxiglumide and O-demethyl dexloxiglumide. Thus, the drug should be prescribed with caution in patients with severe hepatic impairment even though no dose adjustment is warranted. The results of different drug interaction studies have indicated that no clinically relevant metabolic and concomitant drug-drug interactions are expected during the clinical use of dexloxiglumide.

The single-dose pharmacokinetics of the novel CCK1 receptor antagonist, dexloxiglumide, are not influenced by age and gender

OBJECTIVE

The effects of age and gender on the single-dose pharmacokinetics of dexloxiglumide, a selective cholecystokinin (CCK1-subtype) receptor antagonist, were assessed in healthy young and elderly male and female subjects.

METHODS

In total, 24 males and 24 females (12 young and 12 elderly subjects per gender group) received a single oral dose of 200 mg dexloxiglumide under fasted conditions. Mean (range) ages were 23.8 (18 - 32) and 71.3 (66 - 88) years for young and elderly subjects, respectively. Analysis of covariance (ANCOVA) with age group and gender as factors and body weight as a covariate was performed on the dexloxiglumide pharmacokinetic parameters of peak plasma concentration (C(max)) and the area under the plasma concentration-time curve (AUC). The p values obtained from ANCOVA were considered for the assessment of age and gender effects.

RESULTS

A small (approximately 18%) but statistically significant (p < or = 0.036) increase in the area under the plasma concentration-time curve from 0 to time of last quantifiable concentration (AUC(0-t) and the area under the plasma concentration-time curve from 0 to infinity (AUC(0-infinity)) in elderly compared to young subjects was noted. Given the lack of age effects on the other pharmacokinetic parameters of dexloxiglumide, this limited difference is unlikely to be clinically relevant. Without the adjustment for body weights, female subjects exhibited mean C(max) and AUC values approximately 26% and 36% higher than male subjects; however, these exposure differences did not reach statistical significance (p > 0.05) following ANCOVA analysis with body weight as a covariate. Likewise, there were no statistically significant differences (p > 0.05) observed for any other pharmacokinetic parameters between young and elderly and between male and female groups.

CONCLUSIONS

Dose adjustments based on age and gender are not necessary. Dexloxiglumide administration was safe and well tolerated in these subjects.

Pharmacokinetic properties of combination oxycodone plus racemic ibuprofen: two randomized, open-label, crossover studies in healthy adult volunteers

BACKGROUND

As part of ongoing studies to evaluate the analgesic efficacy and pharmacokinetic properties of combination oxycodone plus ibuprofen in the treatment of moderate to severe acute pain, 2 pharmacokinetic studies were conducted.

OBJECTIVES

The goals of these studies were to compare the pharmacokinetic properties of monotherapy with oxycodone or ibuprofen with those of a tablet formulation of these 2 agents combined (study A), and to determine whether the absorption of the individual agents when given in the combination tablet was affected by the concomitant ingestion of food (study B).

METHODS

Study A was a single-center, open-label, randomized, single-dose, 3-period, 3-way, crossover study. Healthy male subjects received oxycodone 5 mg, ibuprofen 400 mg, or a combination tablet containing both, after an overnight fast of > or =8 hours, on study days 1, 8, and 15. Study B was a single-center, open-label, randomized, single-dose, single-crossover study. Healthy volunteers received a tablet containing a combination of oxycodone 5 mg plus ibuprofen 400 mg after either an overnight fast of > or =8 hours or a standardized high-fat breakfast. Both studies included a washout period of > or =7 days between treatments. In both studies, the pharmacokinetic properties (C(max), T(max), t(1/2), AUC(0-4), AUC(0-1), and AUC(0-infinity)) of oxycodone and ibuprofen were derived from plasma drug concentrations. Analysis of variance was used to determine and compare pharmacokinetic properties.

RESULTS

Twenty-four healthy, white, male subjects were included in study A (mean age, 26.0 years; mean body weight, 71.3 kg; mean height, 170.0 cm). Study B involved 12 subjects (11 men, 1 woman; mean age, 24.8 years; mean body weight, 77.2 kg; mean height, 181.4 cm). The pharmacokinetic properties of ibuprofen and oxycodone were not statistically different when administered alone or combined. Food intake did not affect the rate of oxycodone absorption (90% Cl of C(max) of fasted state vs fed state, 103-130), or the rate (90% Cl of C(max) of fasted state vs fed state, 72-95) or extent (90% Cl of AUC(0-infinity) of fasted state vs fed state, 88-102) of ibuprofen absorption. The extent of oxycodone absorption was slightly increased when the combination was given with food (90% Cl of AUC(0-infinity) of fasted state vs fed state, 115-127).

CONCLUSIONS

The single-dose pharmacokinetic profiles of oxycodone and ibuprofen in these healthy volunteers were similar when these 2 drugs were given as monotherapy or in combination, suggesting bioequivalence. Food intake before administration of a single dose of the combination did not affect ibuprofen absorption but marginally increased the extent, but not the rate, of oxycodone absorption.

Interaction of dexloxiglumide, a cholecystokinin type-1 receptor antagonist, with human cytochromes P450

Dexloxiglumide (DEX) is a cholecystokinin type-1 receptor antagonist under development for the treatment of constipation-predominant irritable bowel syndrome. Studies of the potential interaction of DEX with human cytochromes P450 (CYPs) were conducted in vitro. DEX (300 micro M), both with and without a 15-min pre-incubation, was incubated with pooled human liver microsomes and substrates selective for each of eight CYPs. This resulted in >30% inhibition of tolbutamide 4-methyl-hydroxylase (CYP2C9/10) and lauric acid 11-hydroxylase (CYP2E1) activities. Mean K(i) (SD) for CYP2C9/10 and CYP2E1 were 69.0 (24.3) and 426 (60) microM, respectively. Incubations of [(14)C]DEX with pooled human liver microsomes produced one major phase I metabolic fraction, with V(max)=131 pmol/min/mg protein and K(m)=23.7 microM. Further incubations with (i) liver microsomes from 16 individual donors (correlation analysis), (ii) Supersomes trade mark and (iii) selective chemical inhibitors, implicated CYP3A4/5, CYP2B6 and CYP2C9 in the formation of this component. Thus, DEX interacts with CYP2C9 both as inhibitor (K(i)=69.0 microM) and as substrate in vitro. However, based on the maximum concentration (27 microM) after repeated oral doses of 200 mg t.i.d. and the unbound fraction (0.03) of DEX in human plasma, no clinically relevant metabolic interactions with other CYP substrates are predicted.

Characterization of Dexloxiglumide in vitro Biopharmaceutical Properties and Active Transport

The objective of this work was to characterize dexloxiglumide biopharmaceutical properties in vitro and relate these characteristics to its in vivo absorption performance, and to assess dexloxiglumide interaction with P-glycoprotein (P-gp) and MRP1 to anticipate its drug interaction potential. Dexloxiglumide aqueous solubility was moderate and pH dependent. Dexloxiglumide exhibited moderate Caco-2 permeability that was polarized, concentration dependent, and pH dependent. The apical-to-basolateral (AP-BL) permeability at pH 5 [14.5 (+/-1.8) x 10(-6) cm/s] was 2-fold higher than at pH 7.5 [7.24 (+/-0.27) x 10(-6) cm/s]. Neutral and ionized dexloxiglumide species displayed permeabilities of 30.8 (+/-8.4) x 10(-6) cm/s and 9.03 (+/-1.31) x 10(-6) cm/s, respectively. The transport of dexloxiglumide across MDR1-MDCK (P-gp overexpressing Madine Darby canine kidney cells) monolayers was polarized, with a BL-AP/AP-BL permeability ratio of 9.35 (+/-0.73), which was reduced to 1.03 (+/-0.03) by P-gp inhibition. Rhodamine 123 efflux was reduced by dexloxiglumide from 4.06 (+/-0.34) to 2.84 (+/-0.15) across Caco-2 monolayers, and from 17.3 (+/-0.9) to 8.26 (+/-1.38) across MDR1-MDCK monolayers, further indicating dexloxiglumide interaction with P-gp. Additionally, P-gp ATPase activity increased with dexloxiglumide concentration. Dexloxiglumide was effluxed from MRP1-NIH3T3 cells (NIH-3T3 cells expressing the multidrug resistance-associated protein 1). Dexloxiglumide increased MRP1-substrate fluorescein uptake 4-fold, and fluorescein increased dexloxiglumide uptake 1.8-fold. Overall, in vitro transport studies indicate dexloxiglumide to be moderately soluble and moderately permeable, which is in agreement with the incomplete oral absorption of dexloxiglumide. In vitro, dexloxiglumide was moderately modulated by P-gp and MRP1, which provides a rationale for the design of drug interaction studies.

Intravenous and oral antithrombotic efficacy of the novel platelet GPIIb/IIIa antagonist roxifiban (DMP754) and its free acid form, XV459

Currently used antiplatelet drugs, including aspirin, ticlopidine, and others, are effective against certain but not all of the many endogenous platelet activators. Because of their limited efficacy, a significant number of serious thromboembolic complications still occur, highlighting the need for a more effective therapy. DMP754 (roxifiban), a prodrug of XV459, is a recently discovered, potent antiplatelet agent with high affinity and specificity for platelet GPIIb/IIIa receptors that blocks platelet aggregate formation regardless of the agonist (IC(50)=0.030 to 0.05 micromol/L) or anticoagulant used for blood collection. DMP754 rapidly converts to its active free-acid form, XV459, which has a comparable high affinity for both resting and activated platelets (K(d)=1 to 2 nmol/L) and a relatively slow rate of dissociation from resting platelets. The present study was undertaken to determine intravenous and oral antithrombotic efficacies of DMP754 and XV459 and to compare them with those of other antiplatelet and anticoagulant agents in canine models of arterial thrombosis. In these models, thrombosis was induced either electrolytically (200-microA anodal current) in the carotid artery or mechanically by external clamping of the femoral artery along with stenosis, which resulted in either total occlusive thrombus formation or cyclic flow reduction, respectively. DMP754 and XV459 were given either intravenously (0.1 mg/kg bolus) or orally (0.1 to 0.4 mg/kg). Additionally, the antithrombotic efficacies of DMP754, aspirin, heparin, and ticlopidine in the canine carotid artery electrolytic injury model were compared. DMP754 demonstrated oral bioavailability of 20.8% in dogs after administration at different doses and prevented cyclic flow reduction (ED(90-100)=<0.1 mg/kg IV or PO). Additionally, both DMP754 and XV459 (0.1 mg/kg IV or 0.3 to 0.4 mg/kg PO) demonstrated maximal antithrombotic efficacy in preventing electrically induced carotid and coronary artery thrombosis and significant antithrombotic efficacy (P<0.001) at relatively low doses in different settings of arterial thrombosis in the canine model. DMP754 resulted in a significant reduction in thrombus mass and sustained arterial blood flow with 100% prevention of occlusive and nonocclusive thrombosis. In contrast, administration of aspirin (10 mg/kg PO for 2 days), heparin (10 IU/kg IV bolus followed by 90 IU/kg IV infusion over 3 hours), or ticlopidine (300 mg/kg PO for 3 days) before initiation of arterial thrombosis did not reduce the incidence of electrolytic injury-induced occlusive arterial thrombosis. These studies demonstrated a distinct antithrombotic efficacy of DMP754 as compared with existing strategies and suggest potential intravenous and oral antithrombotic uses of DMP754 in the prevention and treatment of thromboembolic disorders.

Disposition and exposure of the fibrinogen receptor antagonist XV459 on alphaIIBbeta3 binding sites in the guinea pig

The disposition of XV459, a potent, selective GP IIb/IIIa antagonist, has been examined following intravenous administration of XP280, the benzenesulphonate salt, and 3H-SA202, the trifluroacetic acid salt, to male guinea pigs. A liquid chromatography-mass spectrometry (LC-MS) method was developed and validated for XV459 quantitation in guinea pig plasma with an LLOQ of 0.1 ng/mL. Intravenous infusions (30 min) of XP280 at doses of 0.5 and 2.0 microg/kg were administered to guinea pigs which were sequentially sacrificed at 0.5, 1, 1.5, 4, 8, 12, 24, 48 and 72 h postinitiation of infusion. Maximum total (unbound and GP IIb/IIIa displaced) XV459 plasma concentration of approximately 3.5 microg/mL was obtained at the 2.0 microg/kg dose. Pooling individual concentration-time data yielded a systemic clearance of 1.42 mL/min/kg, Vss of 0.24 L/kg, and a terminal half-life of 2.8 h in the guinea pig at the 0.5 microg/kg dose. The 2.0 microg/kg dose yielded XV459 exposure that was less than proportional to the previous dose. Similar behaviour has been observed in human trials. Cumulative (up to 72 h) urinary and faecal recovery of total radioactivity was 66.4 and 11.2%, respectively. The time course of spleen, marrow and whole blood radioactivity profiles was similar, suggesting that XV459 was not preferentially sequestered on non-plasma GP IIb/IIIa binding sites. Tissue to blood ratios of 20.7 and 8.3 for the spleen and bone marrow, respectively, indicate that increased (relative to blood) exposure was evident for sites containing the GP IIb/IIIa receptor. In vitro studies confirmed the similarity of XV459 binding to both resting and activated platelets in the guinea pig and humans. Given the comparability of dissociation rate constants and IC50s based on in vitro platelet aggregation, human dosimetry estimates should assume similar partitioning of radiolabelled XV459 as in the guinea pig. These results suggest that the guinea pig may indeed be an appropriate animal model for pharmacokinetic and distribution studies with DMP754; in conjunction with recent pharmacological findings with GP IIb/IIIa antagonists, our results suggest that the guinea pig may be the rodent species of choice for preclinical studies with some other GP IIb/IIIa antagonists.

Oral antiplatelet efficacy and specificity of a novel nonpeptide platelet GPIIb/IIIa receptor antagonist, DMP 802

This study was undertaken to define the platelet glycoprotein alphaIIb beta3 integrin (GPII/IIIa) affinity, specificity, and oral antiplatelet efficacy of DMP 802, a small-molecule nonpeptide antiplatelet agent. Platelet GPIIb/IIIa integrin binding affinity and specificity for DMP 802 were determined by using binding and adhesion assays with cells from various species, including human. DMP 802 demonstrated a potent antiplatelet efficacy [median inhibitory concentration (IC50), 0.029 +/- 0.0042 microM] in inhibiting human platelet aggregation induced by 10 microM adenosine diphosphate (ADP), as assessed by light-transmittance aggregometry. DMP 802 inhibited 125I-fibrinogen binding to activated (ADP, epinephrine, and arachidonic acid at 100 microM each) gel purified human platelets with an IC50 of 0.012 +/- 0.003 microM. DMP 802 demonstrated tight association with unactivated human, baboon, or canine platelets (t(1/2) of dissociation, 32 +/- 2, 32 +/- 13, and 11 +/- 1 min, respectively). DMP 802 binds with high affinity to both unactivated and activated human platelets (Kd = 0.61 +/- 0.17, 0.57 +/- 0.21 nM, respectively). DMP 802 demonstrated species specificity in inhibiting platelet aggregation with IC50 values ranging from 0.025 to 0.092 microM (human, guinea pig, dog, swine, hamster) and 0.88-1.0 microM (rabbit and rat) in platelets obtained from these various species. DMP 802 demonstrated a high degree of specificity for platelet GPIIb/IIIa (alphaIIb/beta3) as compared with other integrins including alpha(v)beta3 (IC50, >10 microM), alpha(v)beta5 (IC50, >100 microM), alpha4beta1 (IC50, >100 microM), and alpha5beta1 (IC50, >10 microM). Oral antiplatelet efficacy of DMP 802 was examined after single oral (0.05-0.20 mg/kg) and after repeated oral dosing at 0.05 mg/kg daily for 5 days in mongrel dogs. Dose-dependent antiplatelet efficacy with an extended duration of antiplatelet efficacy was demonstrated based on ex vivo inhibition of platelet aggregation induced by 100 microM ADP. DMP 802 has an oral bioavailability of 14.9% in dogs. In conclusion, the alpha sulfonamide isoxazoline analog, DMP 802, is a novel oral antiplatelet agent with high affinity, relatively slow dissociation rate and specificity for human platelet GPIIb/IIIa receptors.

Intranasal absorption of the platelet glycoprotein IIb/IIIa receptor antagonist, DMP 755, and the effect of anesthesia on nasal bioavailability

Intranasal absorption and bioavailability of DMP 755, a peptidomimetic, platelet glycoprotein IIb/IIIa receptor antagonist, were examined in anesthetized and lightly sedated dogs. Nasal bioavailability was determined by measuring plasma concentrations relative to those after intravenous dosing. DMP 755 is an ester prodrug, and bioavailability reflects concentrations of the acid hydrolysis product. Nasal bioavailability in dogs anesthetized with pentobarbital was 85 +/- 4%, whereas in dogs anesthetized with the short-acting anesthetic propofol, bioavailability was 32 +/- 7%. Nasal bioavailability was greater than the reported oral bioavailability of DMP 755 in dogs, and was quite consistent. Because anesthesia affects nasal bioavailability, an effect that may depend on the absorption half-life of the test compound, a conscious or lightly sedated animal model is preferred.

Novel nonpeptide antiplatelet glycoprotein IIb/IIIa receptor antagonist, DMP754: receptor binding affinity and specificity

OBJECTIVE

To define the antiplatelet efficacy and specificity of the glycoprotein IIb/IIIa complex (GPIIb/IIIa) antagonist prodrug DMP754 and its free acid form, XV459.

METHODS AND MATERIALS

DMP754 has an IC50 > 1 mumol/l, and, upon its conversion with esterases to its free acid form, demonstrated high potency (IC50 20-45 nmol/l) in inhibiting human platelet aggregation induced by 10 mumol/l adenosine diphosphate, 20 micrograms/ml collagen, 1 mmol/l epinephrine, 10 mumol/l platelet activating factor or 0.5 IU/ml thrombin. The in-vitro rate of hydrolysis of DMP754 or XV459 is much faster with human or canine liver esterases (t 1/2 = 2.4-23 min) than with plasma esterases (t 1/2 = 5.5-7.6 h). Platelet GpIIb/IIIa integrin binding affinity and specificity for XV459 were determined using cell binding/adhesion assays.

RESULTS

The range of IC50 values of XV459 in inhibiting platelet aggregation in platelet-rich plasma obtained from 12 subjects was 0.035-0.069 mumol/l with a mean IC50 of 0.050 +/- 0.003 mumol/l. Additionally, XV459 inhibited platelets obtained from mongrel dogs, baboons, sheep, guinea pigs, and mice with IC50 in the range 0.024-0.06 mumol/l, and IC50 in the range 0.16-5.8 mumol/l in pigs, rabbits, and rats. XV459 inhibited [125I]-fibrinogen binding to activated human platelets with an IC50 of 0.011 +/- 0.003 mumol/l. XV459 demonstrated a high degree of selectivity in specifically inhibiting fibrinogen binding to the platelet integrin, GPIIb/IIIa (IC50 = 0.00025 +/- 0.00005 mumol/l) compared with inhibiting other integrins (alpha v beta 3, IC50 > 10 mumol/l; or alpha v beta 5, alpha 5 beta 1, or alpha 4 beta 1, for which the IC50 exceeded 100 mumol/l).

CONCLUSION

DMP754 is a potent antiplatelet agent in inhibiting platelet aggregation, and has a high specificity and affinity for human platelet GPIIb/IIIa receptors.