An ultrasensitive UPLC-MS/MS assay for the quantification of the therapeutic peptide liraglutide in plasma to assess the oral and nasal bioavailability in beagle dogs.

Aim: An ultrasensitive UPLC-MS/MS assay for liraglutide was developed and validated according to US FDA and EMA guidelines and applied to the quantification of plasma concentrations after intravenous, nasal and oral administration of liraglutide to beagle dogs. Results: Liraglutide isolation was performed with a combined protein precipitation and solid-phase extraction protocol. The calibrated concentration range of 0.1-200 ng/ml was linear with correlation coefficients >0.998. Precise analysis was achieved through the utilization of an isotopically labeled internal standard. Absolute bioavailability of liraglutide after nasal and oral administration of liraglutide to beagle dogs was 0.03 and 0.006%, respectively. Conclusion: The assay matches the performance in sensitivity of the previously applied immunoassay and optimally covers the therapeutic range of liraglutide.

Determination of the Plasma Protein Binding of Liraglutide Using the EScalate* Equilibrium Shift Assay.

The plasma protein binding capability of drug substances represents an important assay parameter in drug discovery and development. For very strong plasma protein binding molecules, however, the free fraction in plasma fu is very small and therefore difficult to determine with standard methods. To solve this problem, the EScalate equilibrium shift in vitro assay was developed. Escalating concentrations of plasma were found to shift the binding equilibrium in solution between the test item and immobilized human serum albumin. Following liquid chromatography coupled to mass spectrometry analysis of the samples, the test compound's fu in plasma is calculated with a 2-dimensional fitting procedure. Comparability of EScalate assay results was demonstrated for 4 extensively studied small molecule drugs (carbamazepine, desipramine, pyrimethamine, and warfarin) as well as for liraglutide, a fatty acid-conjugated peptide drug with very strong plasma protein binding. The results were in good agreement with published data. A free fraction of 0.51% was determined for liraglutide. Our results confirm the compound's very strong plasma protein binding properties in a novel and robust assay system.