Development of an LC-MS/MS method for high throughput quantification of metformin uptake in transporter inhibition...

A high throughput LC-MS/MS method for quantification of metformin substrate uptake enables conversion of radiometric transporter inhibition assays for multidrug and toxin extrusion transporters (MATE 1 and 2) and organic cation transporter 2 (OCT2) to a nonradioactive format. Such conversion greatly simplifies assay complexity and reduces assay costs. The development of a quantitative LC-MS/MS method for metformin in support of the high throughput transporter inhibition assays faced specific challenges of achieving both adequate chromatographic retention and rapid analytical turnaround. Here we report a method that circumvents both challenges. The utilization of a porous graphitic carbon column (Hypercarb) ensured adequate retention of highly polar metformin in biological samples. The combined employment of a ballistic gradient on a 3 mm × 30 mm, 5 μm Hypercarb column, and dual staggered chromatography coupled with multiple injection chromatography acquisition, yielded a fast injection-to-injection cycle time of 30s. The method demonstrated good accuracy, precision and excellent robustness for high throughput applications, and has been successfully implemented in the development and validation of the nonradioactive transporter inhibition assays for MATEs and OCT2.