A radiocalibration method with pseudo internal standard to estimate circulating metabolite concentrations

Area of Science:

• Pharmacokinetics and Metabolism
• Bioanalytical Chemistry
• Drug Development

Background:

• Accurate quantification of circulating human metabolites is crucial for regulatory safety qualification.
• Traditional bioanalytical methods often fail due to the unavailability of metabolite reference standards.

Purpose of the Study:

• To present a novel radiocalibration method for estimating metabolite concentrations in biological samples.
• To address the challenge of analyzing metabolites lacking commercial standards.

Main Methods:

• Development of a radiocalibration assay utilizing a pseudo internal standard (PIS).
• The PIS is incorporated into both radioactive reference and unknown (nonradioactive) samples.
• Metabolite exposure is calculated based on PIS exposure and a predetermined molar ratio.

Main Results:

• The method successfully estimates circulating metabolite concentrations in human and animal plasma.
• Demonstrated the ability to establish human metabolite safety coverage in animal plasma through case studies.
• Validated the method by comparing estimated concentrations with those from direct metabolite calibration.

Conclusions:

• The described radiocalibration method provides a viable solution for quantifying metabolites without available standards.
• This technique supports the development of robust metabolite safety-qualification packages for regulatory submissions.
• The method is effective for both preclinical (animal) and clinical (human) sample analysis.