An investigation of the comparability of commercially sourced plasma and pharmaceutical study plasma, using total protein concentration.

BACKGROUND: Control blood plasma is regularly used in bioanalysis, biomarkers and proteomics, and is often obtained from commercial sources. It has always been assumed that this plasma will be comparable to plasma drawn during a drug development study. RESULTS: When compared using total protein concentrations, plasma from only one species (dog) demonstrated statistical comparability, plasma from all other species tested (human, rabbit, mouse and rat) shows a statistically significant difference. CONCLUSION: If endogenous components of blood plasma are being measured, or if an assay technique does not significantly limit matrix effects, any assay controls should be prepared using control plasma from the drug development site, or using commercial plasma that has been screened against drug development site plasma.

The metabolism and disposition of GSK2140944 in healthy human subjects.

1. GSK2140944 is a novel bacterial topoisomerase inhibitor in development for the treatment of bacterial infections. The metabolism and disposition in healthy human subjects was investigated. 2. Six male subjects received [(14)C] GSK2140944 orally (2000 mg) and as a single 2-hour i.v. infusion (1000 mg). Urinary elimination (59%) was major by the i.v. route, whereas fecal elimination (53%) pre-dominated via the oral route. Accelerator mass spectrometry (AMS) was used for the analysis of plasma and bile samples due to the low level of radioactivity in samples (low specific activity of the doses). Unchanged GSK2140944 was the predominant circulating component (>60% DRM), with the main circulating metabolite M4 formed by oxidation of the triazaacenaphthylene moiety representing 10.8% (considered major) and 8.6% drug-related material by the oral and i.v. route, respectively. Approximately 50% of the oral dose was absorbed and eliminated mainly as unchanged GSK2140944 in urine (∼20% of dose). Elimination via metabolism (∼13% of dose) was relatively minor. The facile oxidation of GSK2140944 to metabolite M4 was believed to be a result of activation by adjacent electron withdrawing groups. 3. This study demonstrates the use of AMS to overcome radioprofiling challenges presented by low specific activity resulted from high doses administration.

Investigation of metabolism and disposition of GSK1322322, a peptidase deformylase inhibitor, in healthy humans using the entero-test for biliary sampling.

GSK1322322 (N-((R)-2-(cyclopentylmethyl)-3-(2-(5-fluoro-6-((S)-hexahydropyrazino[2,1-c][1,4]oxazin-8(1H)-yl)-2-methylpyrimidin-4-yl)hydrazinyl)-3-oxopropyl)-N-hydroxy-formamide) is an antibiotic in development by GlaxoSmithKline. In this study, we investigated the metabolism and disposition of [(14)C]GSK1322322 in healthy humans and demonstrated the utility of the Entero-Test in a human radiolabel study. We successfully collected bile from five men using this easy-to-use device after single i.v. (1000 mg) or oral administration (1200 mg in a solution) of [(14)C]GSK1322322. GSK1322322 had low plasma clearance (23.6 liters/hour) with a terminal elimination half-life of ∼4 hours after i.v. administration. After oral administration, GSK1322322 was readily and almost completely absorbed (time of maximal concentration of 0.5 hour; bioavailability 97%). GSK1322322 predominated in the systemic circulation (>64% of total plasma radioactivity). An O-glucuronide of GSK1322322 (M9) circulated at levels between 10% and 15% of plasma radioactivity and was pharmacologically inactive. Humans eliminated the radioactive dose in urine and feces at equal proportions after both i.v. and oral doses (∼45%-48% each). Urine contained mostly unchanged GSK1322322, accounting for 30% of the dose. Bile contained mostly M9, indicating that glucuronidation was likely a major pathway in humans (up to 30% of total dose). In contrast, M9 was found in low amounts in feces, indicating its instability in the gastrointestinal tract. Therefore, without the Entero-Test bile data, the contribution of glucuronidation would have been notably underestimated. An unusual N-dehydroxylated metabolite (a secondary amide) of GSK1322322 was observed primarily in the feces and was most likely formed by gut microbes.

Metabolism and disposition of vilanterol, a long-acting ß(2)-adrenoceptor agonist for inhalation use in humans.

The metabolism and disposition of vilanterol, a novel long-acting ß(2)-adrenoceptor agonist (LABA) for inhalation use, was investigated after oral administration in humans. Single oral administrations of up to 500 µg of vilanterol were shown to be safe and well tolerated in two clinical studies in healthy men. In a human radiolabel study, six healthy men received a single oral dose of 200 µg of [(14)C]vilanterol (74 kBq). Plasma, urine, and feces were collected up to 168 hours after the dose and were analyzed for vilanterol, metabolites, and radioactivity. At least 50% of the radioactive dose was orally absorbed. The primary route of excretion of drug-related material was via O-dealkylation to metabolites, which were mainly excreted in urine. Vilanterol represented a very small percentage (<0.5%) of the total drug-related material in plasma, indicative of extensive first-pass metabolism. Circulating metabolites resulted mainly from O-dealkylation and exhibited negligible pharmacologic activity. The therapeutic dose level for vilanterol is 25 µg by the inhalation route. At this low-dose level, the likelihood of pharmacologically inactive metabolites causing unexpected toxicity is negligible. In addition to providing an assessment of the disposition of vilanterol in human, this work highlights a number of complexities associated with determining human absorption, distribution, metabolism, and excretion (ADME) for inhaled molecules--mainly related to the low chemical doses and complications associated with the inhalation route of administration.