In drug discovery, human protein
kinases (PKs) represent one of
the major target classes due to their central role in cellular signaling,
implication in various diseases as a consequence of deregulated signaling,
and notable druggability. Individual PKs and their disease biology
have been explored to different degrees, giving rise to heterogeneous
functional knowledge and disease associations across the human kinome.
The U.S. National Institutes of Health previously designated 162 understudied
(“dark”) human PKs and lipid kinases due to the lack
of functional annotations and high-quality molecular probes for functional
investigations. Given the large volumes of available PK inhibitors
(PKIs) and activity data, we have systematically analyzed the distribution
of PKIs and associated data at different confidence levels across
the human kinome and distinguished between chemically explored, underexplored,
and unexplored PKs. The analysis provides a medicinal chemistry-centric
view of PK exploration and further extends prior assessment of the
dark kinome.