Structure-based view of the druggable genome.

International efforts are underway to develop chemical probes for specific protein families, and a 'Target 2035' call to expand these efforts towards a comprehensive chemical coverage of the druggable human genome was recently announced. But what is the druggable genome? Here, we systematically review structures of proteins bound to drug-like ligands available from the Protein Data Bank (PDB) and use ligand desolvation upon binding as a druggability metric to draw a landscape of the human druggable genome. The vast majority of druggable protein families, including some highly populated and disease-associated families, are almost orphan of small-molecule ligands. We propose a list of 46 druggable domains representing 3440 human proteins that could be the focus of large chemical probe discovery efforts.