Solarea Bio (United States)

An absolute bioavailability study that utilized an intravenous [(14)C]microdose was conducted for saxagliptin (Onglyza(®)), a marketed drug product for the treatment of Type 2 diabetes mellitus. Concentrations of [(14)C]saxagliptin were determined by accelerator MS (AMS) after protein precipitation, chromatographic separation by UPLC and analyte fraction collection. A series of investigative experiments were conducted to maximize the release of the drug from high-affinity receptors and nonspecific adsorption, and to determine a suitable quantitation range. A technique-appropriate validation demonstrated the accuracy, precision, specificity, stability and recovery of the AMS methodology across the concentration range of 0.025 to 15.0 dpm/ml (disintegration per minute per milliliter), the equivalent of 1.91-1144 pg/ml. Based on the study sample analysis, the mean absolute bioavailability of saxagliptin was 50% in the eight subjects with a CV of 6.6%. Incurred sample reanalysis data fell well within acceptable limits. This study demonstrated that the optimized sample pretreatment and chromatographic separation procedures were critical for the successful implementation of an UPLC plus AMS method for [(14)C]saxagliptin. The use of multiple-point standards are useful, particularly during method development and validation, to evaluate and correct for concentration-dependent recovery, if observed, and to monitor and control process loss and operational variations.

This chapter contains sections titled: Relevance of AMS to Drug Metabolism Introduction to AMS Fundamentals of AMS Instruments Sample Definition and Interfaces AMS Quantitation LC–AMS Analysis of Drug Metabolites Comparative Resolution of Fraction LC Measurements Quantitative Extraction and Recovery LC–AMS Background and Sensitivity Clinical Aspects of AMS Metabolite Studies AMS Analysis of Reactive Metabolites Species Metabolite Comparison New Metabolic Studies Enabled by AMS Conclusions References

Accelerator mass spectrometers have an energy acceleration and charge exchange between mass definition stages to destroy molecular isobars and allow single ion counting of long-lived isotopes such as (14)C (t½=5370 years.). 'Low' voltage accelerations to 200 kV allow laboratory-sized accelerator mass spectrometers instruments for bioanalytical quantitation of (14)C to 2-3% precision and accuracy in isolated biochemical fractions. After demonstrating this accuracy and precision for our new accelerator mass spectrometer, we discuss the critical aspects of maintaining quantitative accuracy from the defined biological fraction to the accelerator mass spectrometry quantitation. These aspects include sufficient sample mass for routine rapid sample preparation, isotope dilution to assure this mass, isolation of the carbon from other sample combustion gasses and use of high-efficiency biochemical separations. This review seeks to address a bioanalytical audience, who should know that high accuracy data of physiochemical processes within living human subjects are available, as long as a (14)C quantitation can be made indicative of the physiochemistry of interest.

Much of our understanding of vitamin B12 derives from radiocobalt tracer studies conducted decades ago. With new technologies, we can now study B12 absorption and metabolism with unprecedented resolution using almost ambient levels of 14C biosynthetically incorporated into the B12 molecule (14C‐B12). In on‐going studies, a dose of 14C‐B12 (1.3 µg, 50 nCi) in water is administered orally and blood, urine, and feces analyzed for 14C by accelerator mass spectrometry. In 6 subjects, the plasma response was consistent with the expected behavior of peroral B12: 14C‐B12 first appeared in the plasma 3h post‐dose with a peak level within 6‐8h. Urinary and fecal excretion was maximal in the first 24h. The amount of 14C found in the urine (10‐50% of the dose) was 100‐fold greater than in previous reports (0.1‐0.5%), and fecal excretion was lower than expected (<10% vs 30‐70%). Most of the urinary 14C was not associated with intact B12. These results are consistent with metabolism or degradation of the vitamin in the GI tract prior to absorption. The discrepancy between the present and previous findings may be due to the form of radioactive B12 used: 14C labeling the 5,6‐dimethylbenzimidazole moiety in the present study and radiocobalt labeling the corrin ring in previous studies. These findings provide valuable information on the fate of B12 after oral consumption that will inform considerations to fortify the food supply with B12.