Optical control of Class A G protein-coupled receptors with photoswitchable ligands.

The field of photopharmacology of Class A GPCR ligands has recently attracted attention. In this review we analyze 31 papers on currently available photoswitchable ligands for Class A GPCRs. Using the six most recurring terms of all combined paper abstracts, one can extract the overarching goal of this area of research: "Photoswitchable ligands control receptor activity with light" (represented in the TOC graphic). We analyze the design, photochemistry and pharmacology of the photoswitchable ligands. Trends, challenges and limitations will be discussed. A number of efficient photoswitchable ligands that allow optical modulation of GPCR function in various in vitro assays are presented. Moreover, optical modulation of in vivo GPCR function is within reach and the first reports to this end are highlighted.