Leveraging a Clinical Phase Ib Proof-of-Concept Study for the GPR40 Agonist MK-8666 in Patients With Type 2 Diabetes for Model-Informed Phase II Dose Selection.

GPR40 mediates free fatty acid-induced insulin secretion in beta cells. We investigated the safety, pharmacokinetics, and glucose response of MK-8666, a partial GPR40 agonist, after once-daily multiple dosing in type 2 diabetes patients. This double-blind, multisite, parallel-group study randomized 63 patients (placebo, n = 18; 50 mg, n = 9; 150 mg, n = 18; 500 mg, n = 18) for 14-day treatment. The results showed no serious adverse effects or treatment-related hypoglycemia. One patient (150-mg group) showed mild-to-moderate transaminitis at the end of dosing. Median MK-8666 Tmax was 2.0-2.5 h and mean apparent terminal half-life was 22-32 h. On Day 15, MK-8666 reduced fasting plasma glucose by 54.1 mg/dL (500 mg), 36.0 mg/dL (150 mg), and 30.8 mg/dL (50 mg) more than placebo, consistent with translational pharmacokinetic/pharmacodynamic model predictions. Maximal efficacy for longer-term assessment is projected at 500 mg based on exposure-response analysis. In conclusion, MK-8666 was generally well tolerated with robust glucose-lowering efficacy.

The incidence of hypoglycaemia in Muslim patients with type 2 diabetes treated with sitagliptin or a sulphonylurea during Ramadan: a randomised trial.

AIMS: To compare the incidence of symptomatic hypoglycaemia in fasting Muslim patients with type 2 diabetes treated with sitagliptin or a sulphonylurea during Ramadan. METHODS: Patients with type 2 diabetes (age ≥ 18 years) who were treated with a stable dose of a sulphonylurea with or without metformin for at least 3 months prior to screening, who had an HbA(1c) < 10% and who expressed their intention to daytime fast during Ramadan were eligible for this open-label study. Patients were randomised in a 1 : 1 ratio to either switch to sitagliptin 100 mg qd or to remain on their prestudy sulphonylurea. Patients completed daily diary cards to document information on hypoglycaemic symptoms and complications. The primary end-point was the overall incidence of symptomatic hypoglycaemia recorded during Ramadan. RESULTS: Of the 1066 patients randomised, 1021 (n = 507 for sitagliptin and n = 514 for sulphonylurea) returned at least one completed diary card and were included in the analysis. The proportion of patients who recorded one or more symptomatic hypoglycaemic events during Ramadan was lower in the sitagliptin group (6.7%) compared with the sulphonylurea group (13.2%). The risk of symptomatic hypoglycaemia was significantly decreased with sitagliptin relative to sulphonylurea treatment (Mantel-Haenszel relative risk ratio [95% CI] = 0.51 [0.34, 0.75]; p < 0.001). There were no reported events that required medical assistance (i.e. visits to physician or emergency room or hospitalisations) or were considered severe (i.e. events that caused loss of consciousness, seizure, coma or physical injury) during Ramadan. CONCLUSIONS: In Muslim patients with type 2 diabetes who observed the fast during Ramadan, switching to a sitagliptin-based regimen decreased the risk of hypoglycaemia compared with remaining on a sulphonylurea-based regimen. The incidence of hypoglycaemia was lower with gliclazide relative to the other sulphonylurea agents and similar to that observed with sitagliptin.

The Biomarkers Consortium: practice and pitfalls of open-source precompetitive collaboration.

Precompetitive collaboration is a growing driver for innovation and increased productivity in biomedical science and drug development. The Biomarkers Consortium, a public-private platform for precompetitive collaboration specific to biomarkers, demonstrated that adiponectin has potential utility as a predictor of metabolic responses to peroxisome proliferator-activated receptor (PPAR) agonists in individuals with type 2 diabetes. Despite the challenges overcome by this project, the most important lesson learned is that cross-company precompetitive collaboration is a feasible robust approach to biomarker qualification.

Proof of concept: a PhRMA position paper with recommendations for best practice.

Proof of concept (POC) may be defined as the earliest point in the drug development process at which the weight of evidence suggests that it is "reasonably likely" that the key attributes for success are present and the key causes of failure are absent. POC is multidimensional but is focused on attributes that, if not addressed, represent a threat to the success of the project in crucial areas such as safety, efficacy, pharmaceutics, and commercial and regulatory issues. The appropriate weight of evidence is assessed through the use of mathematical models and by evaluating the consequences of advancing a candidate drug that is not safe, effective, or commercially viable, vs. failing to advance a candidate that possesses these attributes. Tools for POC include biomarkers, targeted populations, pharmacokinetic (PK)/pharmacodynamic (PD) modeling, simulation, and adaptive study designs. Challenges to the success of POCs include a shortage of skilled personnel, failure to integrate multiple disciplines and information, and the demand made by organizations for certainty.

Efficacy and safety of sitagliptin when added to insulin therapy in patients with type 2 diabetes.

OBJECTIVE: To evaluate the efficacy and tolerability of sitagliptin when added to insulin therapy alone or in combination with metformin in patients with type 2 diabetes. METHODS: After a 2 week placebo run-in period, eligible patients inadequately controlled on long-acting, intermediate-acting or premixed insulin (HbA1c > or = 7.5% and < or = 11%), were randomised 1:1 to the addition of once-daily sitagliptin 100 mg or matching placebo over a 24-week study period. The study capped the proportion of randomised patients on insulin plus metformin at 75%. Further, the study capped the proportion of randomised patients on premixed insulin at 25%. The metformin dose and the insulin dose were to remain stable throughout the study. The primary endpoint was HbA1c change from baseline at week 24. RESULTS: Mean baseline characteristics were similar between the sitagliptin (n = 322) and placebo (n = 319) groups, including HbA1c (8.7 vs. 8.6%), diabetes duration (13 vs. 12 years), body mass index (31.4 vs. 31.4 kg/m(2)), and total daily insulin dose (51 vs. 52 IU), respectively. At 24 weeks, the addition of sitagliptin significantly (p < 0.001) reduced HbA1c by 0.6% compared with placebo (0.0%). A greater proportion of patients achieved an HbA1c level < 7% while randomised to sitagliptin as compared with placebo (13 vs. 5% respectively; p < 0.001). Similar HbA1c reductions were observed in the patient strata defined by insulin type (long-acting and intermediate-acting insulins or premixed insulins) and by baseline metformin treatment. The addition of sitagliptin significantly (p < 0.001) reduced fasting plasma glucose by 15.0 mg/dl (0.8 mmol/l) and 2-h postmeal glucose by 36.1 mg/dl (2.0 mmol/l) relative to placebo. A higher incidence of adverse experiences was reported with sitagliptin (52%) compared with placebo (43%), due mainly to the increased incidence of hypoglycaemia (sitagliptin, 16% vs. placebo, 8%). The number of hypoglycaemic events meeting the protocol-specified criteria for severity was low with sitagliptin (n = 2) and placebo (n = 1). No significant change from baseline in body weight was observed in either group. CONCLUSION: In this 24-week study, the addition of sitagliptin to ongoing, stable-dose insulin therapy with or without concomitant metformin improved glycaemic control and was generally well tolerated in patients with type 2 diabetes.

Potent and selective agonism of the melanocortin receptor 4 with MK-0493 does not induce weight loss in obese human subjects: energy intake predicts lack of weight loss efficacy.

MK-0493 is a novel, potent, and selective agonist of the melanocortin receptor 4 (MC4R), one of the best-validated genetic targets and considered one of the most promising for the development of antiobesity therapeutics. An ad libitum energy-intake model was qualified with excellent reproducibility: the geometric mean ratio (GMR) with 95% confidence interval (CI) for total energy intake over a period of 24 h for 30 mg sibutramine/placebo was 0.82 (0.76, 0.88), and for 10 mg sibutramine/placebo it was 0.98 (0.91, 1.05). MK-0493 showed a small and marginally significant effect on 24-h energy intake, whereas 30 mg of sibutramine caused a significant reduction in total 24-h energy intake; specifically, the GMR (95% CI) for 30 mg sibutramine/placebo was 0.79 (0.74, 0.85). MK-0493 was associated with modest weight reduction from baseline but had only small, statistically insignificant effects relative to placebo after 12 weeks in a fixed-dose study and also after 18 weeks of stepped-titration dosing. We conclude that agonism of MC4R is not likely to represent a viable approach to the development of antiobesity therapeutics.

Utility of adiponectin as a biomarker predictive of glycemic efficacy is demonstrated by collaborative pooling of data from clinical trials conducted by multiple sponsors.

This study, conducted under the Metabolic Disorders Steering Committee of the Biomarkers Consortium (a public-private partnership managed by the Foundation for the National Institutes of Health (FNIH)), analyzed blinded data on 2,688 type 2 diabetes (T2D) patients from randomized clinical trials conducted by four pharmaceutical companies. An increase in the levels of adiponectin was observed after peroxisome proliferator-activated receptor (PPAR)-agonist treatment (P < 0.0001), but not after treatment with non-PPAR drugs. This increase correlated with decreases in levels of glucose, hemoglobin A(1c) (Hb(A1c)), hematocrit, and triglycerides, and increases in levels of blood urea nitrogen, creatinine, and high-density lipoprotein cholesterol (HDL-C). Early (6-8 weeks) increases in levels of adiponectin after treatment with PPAR agonists showed a negative correlation (r = -0.21, P < 0.0001) with subsequent changes in levels of Hb(A1c). Changes in adiponectin level did not appear to be associated with baseline level of Hb(A1c). Logistic regression demonstrated that an increase in the level of adiponectin predicts a decrease in the level of Hb(A1c). These analyses confirm previously demonstrated relationships between adiponectin levels and metabolic parameters and support the robust predictive utility of adiponectin across the spectrum of glucose tolerance. Cross-company precompetitive collaboration is a feasible and powerful approach to biomarker qualification.

Prevention of chronic anthracycline cardiotoxicity in the adult Fischer 344 rat by dexrazoxane and effects on iron metabolism.

PURPOSE: Anthracyclines, such as doxorubicin and daunorubicin, continue to be widely used in the treatment of cancer, although they share the adverse effect of chronic, cumulative dose-related cardiotoxicity. The only approved treatment in prevention of anthracycline cardiotoxicity is dexrazoxane, a putative iron chelator. Previous in vitro studies have shown that disorders of iron metabolism, including altered IRP1-IRE binding, may be an important mechanism of anthracycline cardiotoxicity. METHODS: This study examined the role of IRP1-IRE binding ex vivo in a chronic model of daunorubicin cardiotoxicity in the Fischer 344 rat and whether dexrazoxane could prevent any daunorubicin-induced changes in IRP1 binding. Young adult (5-6 months) Fischer 344 rats received daunorubicin (2.5 mg/kg iv once per week for 6 weeks) with and without pretreatment with dexrazoxane (50 mg/kg ip). Other groups received saline (controls) or dexrazoxane alone. Rats were killed either 4 h or 2 weeks after the last dose of daunorubicin to assess IRP1-IRE binding. RESULTS: Contractility (dF/dt) of atrial tissue, obtained from rats 2 weeks after the last dose of daunorubicin, was significantly reduced in daunorubicin-treated compared to control rats. Dexrazoxane pretreatment protected against the daunorubicin-induced decrease in atrial dF/dt. However, left ventricular IRP1/IRE binding was not affected by daunorubicin treatment either 4 h or 2 weeks after the last dose of daunorubicin. CONCLUSIONS: IRP1 binding may not be altered in the rat model of chronic anthracycline cardiotoxicity.

Ezetimibe effectively reduces plasma plant sterols in patients with sitosterolemia.

BACKGROUND: Sitosterolemia is a recessively inherited disorder that results from mutations in either ABCG5 or G8 proteins, with hyperabsorption of dietary sterols and decreased hepatic excretion of plant sterols and cholesterol. As a consequence of markedly elevated plasma and tissue sitosterol and campesterol levels, premature atherosclerosis develops. METHODS AND RESULTS: In this multicenter, double-blind, randomized, placebo-controlled study, we examined whether treatment with ezetimibe, an inhibitor of cholesterol absorption, reduces plant sterol levels in patients with sitosterolemia. After a 3-week placebo run-in, 37 patients were randomized to receive placebo (n=7) or ezetimibe 10 mg/d (n=30) for 8 weeks. Sitosterol concentrations decreased by 21% (P<0.001) in patients treated with ezetimibe compared with a nonsignificant 4% rise in those on placebo (between-group P<0.001). The reduction in sitosterol from baseline was progressive, with further decline observed at each subsequent biweekly visit. Campesterol also progressively declined, with a mean decrease after 8 weeks of 24% with ezetimibe and a mean increase of 3% with placebo treatment (between-group P<0.001). Reductions in plant sterol concentrations were similar irrespective of whether patients were undergoing concomitant treatment with resin or statin. Reductions in total sterols and apolipoprotein B were also observed. Ezetimibe was well tolerated, with no serious treatment-related adverse events or discontinuations due to adverse events being reported. CONCLUSIONS: Ezetimibe produced significant and progressive reductions in plasma plant sterol concentrations in patients with sitosterolemia, consistent with the hypothesis that ezetimibe inhibits the intestinal absorption of plant sterols as well as cholesterol, leading to reductions in plasma concentrations.

Interactions between simvastatin and troglitazone or pioglitazone in healthy subjects.

Two randomized, two-period crossover studies were conducted to evaluate the effects of repeat oral dosing of troglitazone (Study I) and pioglitazone (Study II) on the pharmacokinetics of plasma HMG-CoA reductase inhibitors following multiple oral doses of simvastatin and of simvastatin on the plasma pharmacokinetics of troglitazone (Study I) in healthy subjects. In both studies, each subject received two treatments. Treatment A consisted of once-daily oral doses of troglitazone 400 mg (Study I) or pioglitazone 45 mg (Study II) for 24 days with coadministration of once-daily doses of simvastatin 40 mg (Study I) or 80 mg (Study II) on Days 15 through 24. Treatment B consisted of once-daily oral doses of simvastatin 40 mg (Study I) or 80 mg (Study II) for 10 days. In Study I, the area under the plasma concentration-time profiles (AUC) and maximum plasma concentrations (Cmax) of HMG-CoA reductase inhibitors in subjects who received both troglitazone and simvastatin were decreased modestly (by approximately 30% for Cmax and approximately 40% for AUC), but time to reach Cmax (tmax) did not change, as compared with those who received simvastatin alone. Simvastatin, administered orally as a 40 mg tablet daily for 10 days, did not affect the AUC or tmax (p > 0.5) but caused a small but clinically insignificant increase (approximately 25%) in Cmax for troglitazone. In Study II, pioglitazone, at the highest approved dose for clinical use, did not significantly alter any of the pharmacokinetic parameters (AUC, Cmax, and tmax) of simvastatin HMG-CoA reductase inhibitory activity. For all treatment regimens, side effects were mild and transient, suggesting that coadministration of simvastatin with either troglitazone or pioglitazone was well tolerated. The modest effect of troglitazone on simvastatin pharmacokinetics is in agreement with the suggestion that troglitazone is an inducer of CYP3A. The insignificant effect of simvastatin on troglitazone pharmacokinetics is consistent with the conclusion that simvastatin is not a significant inhibitor for drug-metabolizing enzymes. The lack of pharmacokinetic effect of pioglitazone on simvastatin supports the expectation that this combination may be used safely.

Adenosine A1 receptor-dependent and -independent effects of the allosteric enhancer PD 81,723.

The 2-amino-3-benzoylthiophene PD 81,723 has been shown to exhibit allosteric enhancement of adenosine A1 receptor binding and function. The aim of this study was to clarify the mechanism of this effect using membranes purified from rat brain and Chinese hamster ovary (CHO)-A1 cells that stably express the rat adenosine A1 receptor as well as intact CHO-A1 and nontransfected CHO cells. In membranes containing 100 microM magnesium, (2-amino-4, 5-dimethyl-3-thienyl)-[3-(trifluoromethyl)phenyl]methanone (PD 81, 723) significantly increased the affinity of the adenosine A1 receptor agonist, cyclopentyladenosine, for the low-affinity receptor without affecting high-affinity binding or Bmax. In intact cells, PD 81,723 inhibited basal adenylyl cyclase (AC) activity as well as forskolin-, cholera toxin-, and pertussis toxin-stimulated AC activity in CHO-A1 and CHO cells. Basal AC activity was inhibited 49% in CHO and 82% in CHO-A1 cells by 30 microM PD 81,723. In CHO-A1 cells, half-maximal inhibition of forskolin-stimulated AC occurred at 5 microM PD 81,723 compared to 10 microM in CHO cells. Cholera toxin-stimulated AC was reduced 90% in both CHO and CHO-A1 cells by 30 microM PD 81,723. At the same concentration of PD 81,723, pertussis toxin-stimulated AC activity was reduced 86% (CHO-A1) and 77% (CHO). [3H]forskolin was displaced from purified rat liver AC by PD 81,723 with an IC50 of 96 microM. These results demonstrate that two mechanisms appear to contribute to the observed effects of PD 81, 723. One mechanism is allosteric enhancement of adenosine A1 receptor function. Results from transfected and nontransfected cells suggest that PD 81,723 also inhibits AC directly by binding to the catalytic unit at or near the forskolin-binding site.

A solid-phase radioimmunoassay for cyclic AMP.

A solid-phase radioimmunoassay for cAMP in tissues, body fluids, and cultured cells has been developed using 125I-2'-O-monosuccinyl adenosine-3':5'-cyclic monophosphate tyrosyl methyl ester and High Binding EIA microtiter strips coated overnight at 4 degrees C with a rabbit or sheep polyclonal anti-cAMP antibody. After washing and blocking of wells, samples or standards were added, followed by the addition of radiolabel. Bound 125I-cAMP was separated from free by washing with phosphate buffer containing Tween 20. Bound 125I-cAMP was inversely proportional to cAMP in samples or standards. Cyclic AMP content of unknowns was calculated from a standard curve run concurrently with each assay. Both antibodies showed sensitivity of approximately 1 fmol, an assay range between 15 and 1,000 fmol, a maximum displacement ratio of up to 11-12, and no cross-reactivity with other cyclic nucleotides. Recoveries were 86.5%-106.8%, intraassay coefficients of variation were 2.4%-6.0%, and interassay coefficients of variation were 7.4%-10.2% for both antibodies. The cAMP content of tissues (brain > heart > kidney, liver > muscle) from rat, rabbit, and guinea pig, cultured rat lymphocytes from three lymphoid tissues, and human serum and urine were tested. This solid-phase RIA is a reliable, sensitive, rapid, and relatively inexpensive method for determination of cAMP.

Species comparison of adenosine and beta-adrenoceptors in mammalian atrial and ventricular myocardium.

The antagonist radioligand 1,3-[3H]dipropyl-8-cyclopentylxanthine ([3H]DPCPX) was used to characterize adenosine A1 receptors in membrane preparations from atrial and ventricular myocardium of rat, rabbit, guinea pig and pig. Kd values in crude membranes from guinea pig atria and ventricles (3.3 and 3.0 nM) were higher than those in the other species (ranges, 1.5-1.8 and 1.5-1.9 nM). Bmax values were greater in atria than in ventricles in all four species, and in atria and ventricles of guinea pig (76 and 34 fmol/mg), than in the other species (ranges, 15-17 and undetectable to 12 fmol/mg). In contrast, guinea pig Kd and Bmax values for beta-adrenoceptors, which were labelled with (-)3-[125I]iodocyanopindolol, fell within the range of values for the other three mammalian species. In semipurified membrane preparations from pig, [3H]DPCPX and the agonist radioligand [125I]-N6-4-aminobenzyladenosine appeared to label a similar population of receptors and gave comparable Kd values in atria (0.73 and 0.66 nM) and in ventricles (0.57 and 0.70 nM). In semipurified preparations from pig, the agonist R-(-)-N6-(2-phenylisopropyl)adenosine (R-PIA) displaced [3H]DPCPX in a manner consistent with the presence of both high- and low-affinity adenosine A1 receptors. The data from this study indicate that the density of adenosine A1 receptors in atria is greater than in ventricles, but similar Kd values suggest that the A1 receptor population is the same in the two cardiac tissues. Also, the data demonstrate that the [3H]DPCPX antagonist binding characteristics of guinea pig myocardium differ from those in rat, rabbit and pig.

Cimetidine inhibits theophylline clearance in patients with chronic obstructive pulmonary disease: a study using stable isotope methodology during multiple oral dose administration.

1 The effect of concurrent cimetidine administration on the disposition of theophylline was investigated in eight male patients (56-78 years) with chronic obstructive pulmonary disease (COPD). 2 The patients, who were taking oral theophylline preparations chronically (384-1020 mg/day), received a [15N], [13C]-labelled analogue of theophylline (10 mg i.v.) before and during cimetidine treatment (1200 mg/day p.o.). 3 During cimetidine treatment trough levels of theophylline increased 34% (6.4 +/- 0.8 to 8.6 +/- 1.0 micrograms/ml, P less than 0.05), half-life increased 48% (6.5 +/- 0.6 to 9.6 +/- 0.8 h, P less than 0.001), and total plasma clearance decreased 33% (3.88 +/- 0.46 to 2.59 +/- 0.33 l/h, P less than 0.001), without a significant change in volume of distribution or protein binding. 4 The effect of cimetidine on plasma levels of theophylline was maximal within 72 h. Levels returned to control values within 48 h after its discontinuation. 5 Although there was no correlation with mean plasma concentrations of cimetidine, the change in clearance of theophylline correlated with initial clearance values (r = 0.72). 6 Cimetidine reduced the plasma clearance of theophylline in patients with COPD to an extent similar to that reported in healthy volunteers.

Effect of intravenous aminophylline on plasma levels of catecholamines and related cardiovascular and metabolic responses in man.

Theophylline is thought to act by inhibiting the activity of phosphodiesterase, with a resultant increase in intracellular cyclic AMP. However, this concept is largely based on in vitro studies using concentrations of theophylline which greatly exceed therapeutic plasma concentrations. To investigate the relationship of the cardiovascular and metabolic effects of theophylline to activation of the sympathetic nervous system, i.v. aminophylline was administered to six healthy males under basal conditions. Each subject received four infusions. Mean theophylline concentrations (+/- SEM) of 4.5 +/- 0.2, 10.0 +/- 0.5, 14.0 +/- 0.5 and 20.0 +/- 1.2 micrograms/ml were achieved. Plasma epinephrine increased 262% (from 29 +/- 4 to 105 +/- 14 pg/ml, p less than 0.01) and plasma norepinephrine increased 64% (from 190 +/- 18 to 312 +/- 51 pg/ml, p less than 0.05) during the high-dose infusion. The increases in circulating catecholamines were dose-related (p less than 0.001 by analysis of variance). Dose-related increases in heart rate, systolic blood pressure, plasma glucose, free fatty acids and insulin were also observed (p less than 0.001 by analysis of variance). Although the duration of total electromechanical systole (QS2) and left ventricular ejection time adjusted for heart rate fell during the aminophylline infusions, this positive inotropic response was not influenced by dose, except possibly the high dose. Echocardiographic ejection fraction was not changed by the aminophylline infusions. We conclude that the acute cardiovascular and metabolic effects of theophylline may be mediated in part by stimulation of the sympathetic nervous system.

Stable isotope methodology in a pharmacokinetic study of the interaction of theophylline and cimetidine.

Theophylline administered orally and (1,3-15N,2-13C)theophylline administered intravenously in tracer quantities were used to investigate under steady-state conditions the interaction of theophylline with cimetidine in a patient with chronic obstructive pulmonary disease. Both compounds were quantified simultaneously by mass spectral analysis after solvent extraction and high pressure liquid chromatographic purification of plasma samples. The assay is reliable and accurate to a plasma level of 50 ng ml-1 for the stable isotope tracer with a practical lower limit of detection of 10 ng ml-1.