G-protein-coupled receptors (GPCRs) are the largest and most diverse group of membrane receptors in eukaryotes that detect molecules outside the cell and activate internal signal transduction pathways and, ultimately, cellular responses. GPCRs are involved in nearly every aspect of animal life, from early development and heart function to neuronal activity. Mutations in GPCRs are linked to a number of human diseases. GPCRs are an important drug target and approximately 34% of the marketed drugs target 108 members of this family, with an additional 66 receptors targeted by agents that are/were in clinical trials. GPCR-based drug discovery remains active campaigns in major pharmaceutical companies. To date more than 140 orphan GPCRs, whose endogenous ligands are unknown, are the focus of an intense drug discovery effort in many programs.

Specifically, the optimal ligands to GPCRs need to possess high affinity and specificity for the target protein, and reasonable membrane permeability for biological activity in whole cell assays and in vivo models. GPCR Compound Library from TargetMol, a focused small molecule libraries developed against particular GPCRs containing 2223 GPCR-active agents for GPCR drug discovery.