Disposition and metabolism of darapladib, a lipoprotein-associated phospholipase A2 inhibitor, in humans.

The absorption, metabolism, and excretion of darapladib, a novel inhibitor of lipoprotein-associated phospholipase A2, was investigated in healthy male subjects using [(14)C]-radiolabeled material in a bespoke study design. Disposition of darapladib was compared following single i.v. and both single and repeated oral administrations. The anticipated presence of low circulating concentrations of drug-related material required the use of accelerator mass spectrometry as a sensitive radiodetector. Blood, urine, and feces were collected up to 21 days post radioactive dose, and analyzed for drug-related material. The principal circulating drug-related component was unchanged darapladib. No notable metabolites were observed in plasma post-i.v. dosing; however, metabolites resulting from hydroxylation (M3) and N-deethylation (M4) were observed (at 4%-6% of plasma radioactivity) following oral dosing, indicative of some first-pass metabolism. In addition, an acid-catalyzed degradant (M10) resulting from presystemic hydrolysis was also detected in plasma at similar levels of ∼5% of radioactivity post oral dosing. Systemic exposure to radioactive material was reduced within the repeat dose regimen, consistent with the notion of time-dependent pharmacokinetics resulting from enhanced clearance or reduced absorption. Elimination of drug-related material occurred predominantly via the feces, with unchanged darapladib representing 43%-53% of the radioactive dose, and metabolites M3 and M4 also notably accounting for ∼9% and 19% of the dose, respectively. The enhanced study design has provided an increased understanding of the absorption, distribution, metabolism and excretion (ADME) properties of darapladib in humans, and substantially influenced future work on the compound.

Assessment of potential drug interactions by characterization of human drug metabolism pathways using non-invasive bile sampling.

AIM: Characterization of the biliary disposition of GSK1325756, using a non-invasive bile sampling technique and spectrometric analyses, to inform the major routes of metabolic elimination and to enable an assessment of victim drug interaction risk. METHOD: Sixteen healthy, elderly subjects underwent non-invasive bile capture using a peroral string device (Entero-Test(®)) prior to and following a single oral dose of GSK1325756 (100 mg). The device was swallowed by each subject and once the weighted string was judged to have reached the duodenum, gallbladder contraction was stimulated in order to release bile. The string was then retrieved via the mouth and bile samples were analyzed for drug-related material using spectrometric and spectroscopic techniques following solvent extraction. RESULTS: Nuclear magnetic resonance spectroscopy (NMR) indicated that the O-glucuronide metabolite was the major metabolite of GSK1325756, representing approximately 80% of drug-related material in bile. As bile is the major clearance route for GSK1325756 (only 4% of the administered dose was excreted in human urine), this result indicates that uridine 5'-diphospho-glucuronosyltransferases (UGTs) are the major drug metabolizing enzymes responsible for drug clearance. The relatively minor contribution made by oxidative routes reduces the concern of CYP-mediated victim drug interactions. CONCLUSION: The results from this study demonstrate the utility of deploying the Entero-Test® in early human studies to provide information on the biliary disposition of drugs and their metabolites. This technique can be readily applied in early clinical development studies to provide information on the risk of interactions for drugs that are metabolized and eliminated in bile.

Disposition and metabolism of [14C]SB-649868, an orexin 1 and 2 receptor antagonist, in humans.

N-[[(2S)-1-[[5-(4-fluorophenyl)-2-methyl-4-thiazolyl]carbonyl]-2-piperidinyl]methyl]-4-benzofurancarboxamide (SB-649868) is a novel orexin 1 and 2 receptor antagonist under development for insomnia treatment. The disposition of [(14)C]SB-649868 was determined in eight healthy male subjects using an open-label study design after a single oral dose of 30 mg. Blood, urine, and feces were collected at frequent intervals after dosing, and samples were analyzed by high-performance liquid chromatography-mass spectrometry coupled with off-line radiodetection for metabolite profiling and characterization. NMR spectroscopy was also used to further characterize certain metabolites. Elimination of drug-related material was almost complete over a 9-day period, occurring principally via the feces (79%), whereas urinary excretion accounted only for 12% of total radioactivity. Mean apparent half-life (t(1/2)) of plasma radioactivity was notably longer (39.3 h), with respect to that of unchanged SB-649868 (4.8 h), suggesting the presence of more slowly cleared metabolites. SB-649868 and an unusual hemiaminal metabolite, M98 (2-[((2S)-1-{[5-(4-fluorophenyl)-2-methyl-1,3-thiazol-4-yl]carbonyl}-2-piperidinyl)methyl]-3,5-dihydroxy-3,4-dihydro-1(2H)-isoquinolinone; GSK2329163), resulting from oxidation of the benzofuran ring and subsequent rearrangement, were the principal circulating components in plasma extracts. Two additional minor metabolites were also observed: a benzofuran ring-opened carboxylic acid M25 ([2-({[((2S)-1-{[5-(4-fluorophenyl)-2-methyl-1,3-thiazol-4-yl]carbonyl}-2-piperidinyl)methyl]amino}carbonyl)-6-hydroxyphenyl]acetic acid; GSK2329158) and an amine metabolite (M8). SB-649868 was extensively metabolized, and only negligible amounts were excreted unchanged. The principal route of metabolism was via oxidation of the benzofuran ring with the resultant M25 being the principal metabolite in excreta, representing at least 12% of the administered dose across urine and feces.

Mental health and long-term conditions 2: Managing depression.

This second article in a two-part series on mental health and long-term conditions discusses the complex area of comorbid physical health and mental health problems. It focuses on depression--one of the most common mental illnesses--examining its prevalence and symptoms in people with long-term conditions, and how it can affect the ability to self-manage them. It also examines how nurses can support clients who experience depression as part of their long-term condition.

Mental health and long-term conditions.1: Physical health.

Poor diet, smoking, a lack of physical activity and excessive alcohol intake are just some of the factors that can contribute to a range of debilitating long-term conditions. Lifestyle risk factors can have a disproportionate impact on more vulnerable groups within society, such as people with mental health problems. In the first in a two-part series on mental health and long-term conditions, this article looks at the prevalence of physical illness among this service user group and how this affects mortality and morbidity. It also examines factors influencing physical health, and discusses the role nurses can play in screening for physical conditions in vulnerable groups.

Approaches for the rapid identification of drug metabolites in early clinical studies.

Understanding the metabolism of a novel drug candidate in drug discovery and drug development is as important today as it was 30 years ago. What has changed in this period is the technology available for proficient metabolite characterization from complex biological sources. High-efficiency chromatography, sensitive MS and information-rich NMR spectroscopy are approaches that are now commonplace in the modern laboratory. These advancements in analytical technology have led to unequivocal metabolite identification often being performed at the earliest opportunity, following the first dose to man. For this reason an alternative approach is to shift from predicting and extrapolating possible human metabolism from in silico and nonclinical sources, to actual characterization at steady state within early clinical trials. This review provides an overview of modern approaches for characterizing drug metabolites in these early clinical studies. Since much of this progress has come from technology development over the years, the review is concluded with a forward-looking perspective on how this progression may continue into the next decade.