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The background to human microdosing or Phase 0 studies is reviewed, focusing particularly on the information that such studies can provide in the context of exploratory clinical development. Examples are provided of the microdose-validation studies known as the Consortium for Resourcing and Evaluating AMS Microdosing trial and EU Microdosing AMS Partnership Programme, which demonstrated that there was good dose proportionality between microdose and pharmacological dose pharmacokinetics. When microdosing was applied to ten development drugs, it was found that all ten molecules showed dose proportionality between the microdose and the pharmacological dose. The majority of microdose studies have used accelerator mass spectrometry (AMS) analysis and only these studies that are considered here; AMS provides information on all metabolites, even if these are minor. There is now sufficient scientific data to justify microdose studies being routinely conducted as part of the drug-development process. © 2010 Future Science Ltd.

Lappin G.,University of Lincoln | Boyce M.J.,Hammersmith Medicines Research | Matzow T.,Hammersmith Medicines Research | Seymour M.,Xceleron Ltd | Warrington S.J.,Hammersmith Medicines Research
European Journal of Clinical Pharmacology | Year: 2013

Purpose: To explore, in a microdose (phase-0) study, the pharmacokinetics, bioavailability and concentrations in key compartments of the lung, of AR-709, a novel diaminopyrimidine antibiotic for the treatment of respiratory infection. Methods: Four healthy men each received two single, 100 μg microdoses of 14C-AR-709, 7 days apart: the first was administered intravenously (IV), the second orally. Plasma pharmacokinetics of 14C and unchanged AR-709 were obtained by high-performance liquid chromatography and accelerator mass spectrometry (AMS). Next, 15 healthy men received a single, 100 μg microdose of 14C-AR-709 IV. Plasma, bronchoalveolar lavage fluid, alveolar macrophages and bronchial mucosal biopsy samples were analysed by AMS. Results: After IV administration, clearance of AR-709 was 496 mL/min, volume of distribution was 1,700 L and the absolute oral bioavailability was 2.5 %. Excretion in urine was negligible. At 8-12 h after IV dosing, 14C concentrations in lung samples were 15- (bronchial mucosa) to 200- (alveolar macrophages) fold higher than in plasma. In alveolar macrophages, 14C was still mostly associated with AR-709 at 12 h after dosing. Conclusions: The results of this microdose study indicate that AR-709 attains concentrations appreciably higher within the lung than in plasma. Its low oral bioavailability however, precludes oral administration. Although IV administration would appear to be an effective route of administration, this would limit the use of AR-709 to a clinical setting and would therefore be economically unsustainable. If further clinical development were to be undertaken, therefore, an alternative route of administration would be necessary. © 2013 Springer-Verlag Berlin Heidelberg.

Garner R.C.,Xceleron Ltd | Garner R.C.,University of York
Journal of Labelled Compounds and Radiopharmaceuticals | Year: 2010

The enabling technology of accelerator mass spectrometry (AMS) permits ultrasensitive analysis of14C in the attogram to zeptogram range. As a result AMS analysis is being used in drug development to measure drug concentrations from human clinical studies conducted with very low amounts (nanoCuries) of administered radiolabel. The administered radiolabel can be at high specific radioactivity as in Phase 0 microdose studies or at much lower specific radioactivity as in metabolite profiling/mass balance and absolute bioavailability studies. Each of these study designs can give essential human ADME/PK information enabling drugs to be developed more effectively than using conventional approaches. Copyright © 2010 John Wiley & Sons, Ltd.

Lappin G.,Xceleron Ltd
Bioanalysis | Year: 2010

The concept of microdosing has been around for approximately 10 years. In this time there have been an increasing number of drugs reported in the literature where the pharmacokinetics at a microdose have been compared with those observed at a therapeutic dose. Currently, approximately 80% of the microdose pharmacokinetics available in the public domain have been shown to scale to those observed at a therapeutic dose, within a twofold difference. Microdosing is now being extended into areas of drug development other than purely pharmacokinetic prediction. Microdosing has been applied to the study of drug-drug interactions by giving human volunteers a microdose of the candidate drug before and after the administration of a drug known to inhibit or induce certain enzymes, such as the cytochrome P450s. Early data on the metabolism of a drug candidate can be obtained by administering a 14C-drug to human volunteers and comparing the plasma concentration-time curves for total 14C and unchanged parent compound. Full metabolic profiles can be generated as an early indication of the drug's metabolism in humans, prior to Phase 1 clinical studies. Microdosing is also being applied to situations where the concentration of a drug in cell or tissue types is key to its efficacy. The application of microdosing as a tool in drug development is therefore widening into new and previously unforeseen fields. © 2010 Future Science Ltd.

Higton D.,Redx Anti Infectives Ltd. | Seymour M.,Xceleron Ltd
Bioanalysis | Year: 2014

Since its introduction into the drug-development arena, accelerator mass spectrometry (coupled with liquid chromatography fractionation) has been used to support a variety of study types. The uses to which the technique has been put include parent and/or metabolite quantification in pharmacokinetic studies, total radioactivity measurement in adsorption, metabolism and excretion studies, and quantitative metabolite profiling. A tiered approach has been applied to the verification of accelerator mass spectrometry assays, dependant on in which type of study and at what stage of drug development they are used. As accelerator mass spectrometry is an absolute detector that can quantify without the use of analyte-related standards, the specific assay verification requirements differ from those for LC-MS/MS assays. This article describes when screening, qualified and validated assay verification procedures should be applied, and suggests what parameters should be assessed in each case. © 2014 Future Science Ltd.

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