Polypharmacology of an Optimal Kinase Library

Despite decades of research, current understanding of the spectrum of targets bound by kinase inhibitors remains incomplete. This complicates mechanism of action studies, drug repurposing, and understanding of adverse responses. Here, we describe kinome-wide profiling of an optimal kinase library (OKL) comprising 192 small molecules selected based on stage of clinical development, chemical diversity, and target coverage. Our results show that polypharmacology is widespread among kinase inhibitors independent of regulatory approval. The generally understood ("assigned") targets of approved molecules are not necessarily the most potently inhibited and off targets include multiple understudied kinases. Moreover, median selectivity has not increased over time. We illustrate the use of synoptic OKL-kinome profiles in identifying potential toxicity targets, repurposing anti-inflammatory drugs for neurodegenerative and infectious diseases, and performing chemical genetic studies. Our studies illustrate how much remains to be discovered about the chemistry and biology of one of the largest classes of human therapeutics.