Chemical coverage of human biological pathways

•Only 2.2% of human proteins are targeted by chemical probes, 1.8% by chemogenomic compounds, and 11% by drugs.•Chemical tools developed by Target 2035 are already covering 50% of human pathways and represent a versatile toolkit to interrogate human biology.•Pathways enriched in drugs and deprived of chemical tools could be prioritized by Target 2035.•Alternatively, targeting pathways with low or no chemical coverage will enable the exploration of unknown biology. Chemical probes and chemogenomic compounds are valuable tools to link gene to phenotype, explore human biology, and uncover novel targets for precision medicine. The mission of the Target 2035 initiative is to discover chemical tools for all human proteins by the year 2035. Here, we draw a landscape of the current chemical coverage of human biological pathways. Although available chemical tools target only 3% of the human proteome, they already cover 53% of human biological pathways and represent a versatile toolkit to dissect a vast portion of human biology. Pathways targeted by existing drugs may be enriched in unknown but valid drug targets and could be prioritized in future Target 2035 efforts.