A mimetic tissue model for the quantification of drug distributions by MALDI imaging mass spectrometry

The full potential of imaging mass spectrometry (IMS) as a tool in drug development will not be realized until reliable quantitative information can be integrated with the molecular distributions. Here we report a novel method for the quantification of drugs in tissue sections using matrix-assisted laser desorption/ionization (MALDI) IMS. This method uses a mimetic tissue model consisting of a set of tissue homogenates spiked with a range of different drug concentrations that have been frozen into a polymer support mold. The goal of this model is to mimic a dosed tissue in its effects on analyte extraction and ion suppression. Parallel preparation and analysis of sections from the tissue model and the dosed tissues allow for the quantification of a drug's distribution. Here we detail the steps involved in constructing the model and provide proof of concept data to highlight the potential of this approach. Several figures of merit are evaluated including linearity of response, variability, and section-to-section reproducibility. Finally, the tissue model is used to quantify two different drugs, lapatinib and nevirapine, in dosed tissues from nonclinical species and the results are compared with those generated by LC-MS quantification.