Mitigating Nephrotoxicity Risks and Ranking Drug Candidates Using MALDI Mass Spectrometry Imaging: A Case Study.

Drug-induced nephrotoxicity is a major challenge in drug discovery and development, accounting for nearly a quarter of severe adverse effects in current pharmacotherapy. Antimicrobial use may be associated with this problem, with one-third of nephrotoxicity related to these drugs. During the lead optimization stage of our antibacterial programs, nephrotoxicity was observed with renal tubule degeneration and tubular granular casts. To examine the nephrotoxicity mechanisms and triage compounds, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was used to investigate the compound distribution in rat kidney sections. MALDI-MSI has emerged as a powerful tool allowing for the spatial localization of drugs and metabolites directly from tissue surfaces without the need for labels. By comparing the renal distribution of toxic and non-toxic compounds, a correlation of preferential renal cortex and outer-medullar distribution with positive in vivo nephrotoxicity was discovered for most of the drug candidates being tested. This correlation facilitated the ranking of compounds to aid in the lead optimization process of antimicrobial drug discovery. We envision that MALDI-MSI can be used for drug-induced nephrotoxicity derisking during drug discovery and development when a correlation between tissue distribution and nephrotoxicity can be established.