Highly Multiplexed Kinase Profiling in Spleen with Targeted Mass Spectrometry Reveals Kinome Plasticity across Species

Early attrition of drug candidates,
including kinase inhibitors,
often occurs due to issues that arise during preclinical safety and
efficacy evaluation. This problem may be exacerbated by the fact that
these studies might fail to consider the basic physiological differences
that could exist between human patients and animal models. We report
the development of a targeted mass spectrometry-based assay capable
of monitoring >50 different kinases using peptides conserved in
humans
and the key preclinical species used in drug development (mouse, rat,
dog, and cynomolgus monkey). These methods were then used to profile
interspecies kinome variability in spleen with three of the current
techniques used in targeted proteomics (MRM, PRM, and IS-PRM). IS-PRM
provides the highest number of kinase identifications, and the results
indicate that while this initial set of kinases exhibits high correlation
between species for this tissue type, distinct species-specific differences
do exist, especially within the cyclin-dependent kinase family. An
initial screen in two species with the kinase inhibitor dasatinib
in competition with the chemoproteomic kinase-binding probe XO44 demonstrated
how the targeted methods can be further applied to study species-specific
inhibitor occupancy profiles. Understanding such differences could
help rationalize the findings of preclinical studies and have major
implications for the selection of these animals as models in kinase
drug development.