Quantifying exploratory low dose compounds in humans with AMS

Abstract

Accelerator Mass Spectrometry is an established technology whose essentiality extends beyond simply a better detector for radiolabeled molecules. Attomole sensitivity reduces radioisotope exposures in clinical subjects to the point that no population need be excluded from clinical study. Insights in human physiochemistry are enabled by the quantitative recovery of simplified AMS processes that provide biological concentrations of all labeled metabolites and total compound related material at non-saturating levels. In this paper, we review some of the exploratory applications of AMS 14C in toxicological, nutritional, and pharmacological research. This body of research addresses the human physiochemistry of important compounds in their own right, but also serves as examples of the analytical methods and clinical practices that are available for studying low dose physiochemistry of candidate therapeutic compounds, helping to broaden the knowledge base of AMS application in pharmaceutical research.

Simultaneous oral therapeutic and intravenous 14C‐microdoses to determine the absolute oral bioavailability of saxagliptin and dapagliflozin

“…Simultaneous dosing of a therapeutic oral dose with an intravenous 14 C-microdose, and detection with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and accelerator mass spectrometry (AMS), respectively, has not been widely used for determining the absolute bioavailability of new chemical entities due to uncertainties surrounding AMS accuracy and health authority views on this approach.…”

“…• Using a simultaneous intravenous 14 C-microdose given at the tmax of an orally administered unlabelled drug, and analysis using AMS detection, is a resource-saving and viable approach to determine the absolute bioavailability of a new chemical entity, provided a robust AMS method is used. The absolute bioavailability values of two new diabetes medicines, saxagliptin and dapagliflozin, were determined using this approach to characterize fully their pharmacokinetics.…”

“…doses were assayed by AMS following sample preparation using protein precipitation, LC-fractionation and sample graphitization. The LLOQ of the assay was determined to be the concentration where the presence of saxagliptin and dapagliflozin could be reliably differentiated from the background 14 C observed in the pre-dose study samples and the limit of detection of the AMS. The AMS methods were validated for accuracy, precision and selectivity prior to the analysis of study samples.…”

“…The validation for the saxagliptin assay, which did use a standard curve, also demonstrated the accuracy, precision, stability, specificity and recovery of the method across the concentration range of 0.025 to 15.0 dpm min -1 ml -1 , equivalent to 1.91 to 1144 pg ml -1 [12]. The results from two accuracy/precision (A/P) runs showed that application of a traditional validation approach which utilized standard plots, quality controls and stability assessments to AMS methods can meet widely accepted bioanalytical criteria for accuracy and precision (Ϯ15% in general or Ϯ20% for the LLOQ) [13,14]. Dilution integrity up to three fold, processed stability up to 384 h and frozen sample in matrix stability up to 52 days at -20°C were also demonstrated through the two A/P runs.…”

To Apply Microdosing or Not? Recommendations to Single Out Compounds with Non-Linear Pharmacokinetics

“…Microtracer and microdosing studies, enabled by accelerator mass spectrometry (AMS) to ultrasensitively quantify radiolabeled compounds in biological matrices, offer various strategic advantages in drug development [1]. In microtracer studies, a low dose of radiolabeled compound is added to a high dose of the unlabeled compound or a potentially interacting drug, by the same or alternate routes of administration.…”