Category: Drug Target Strategies
Trace metals play important structural and functional roles in the biochemistry of many drug targets. We recently suspected that enzyme samples prepared for our JMJD3 program in the Pfizer Centers for Therapeutic Innovation portfolio were contaminated with at least one stoichiometric equivalent of a transition metal and were challenged with identifying the unknown species. Complicating to this is the fact that that drug target preparations are often generated on the microscale, and it can take weeks to prepare only a few milligrams of sample. Thus, we needed a technique that was acutely sample-sparing. Here we report the use of an Xray Fluorescence Spectroscopy Microplate Reader to interrogate trace element contamination of samples on the microscale, and confirmed the biochemical relevance of our observations with Native Mass Spectrometry. These methods were able to determine Period 4 transition metal contamination with single-digit micromolar limits of quantitation, and consumed only 100-200 µL of total sample. We anticipate that the approach outlined here should be broadly applicable to early discovery portfolios where drug targets are typically under-studied and the knowledge of metal ion content may have a profound impact on the prosecution of associated projects.
Timothy Foley– Principal Scientist, Pfizer, Groton, CT