Photopharmacology: A Definition

 

 

 

Photopharmacology

(Angew. Chem. Int. Ed. 2016, 55, 10978–10999; J. Am. Chem. Soc. 2014, 136, 2178–2191)

 

The concept of photopharmacology encompasses the introduction of photo-responsive/photoswitchable substructures into the pharmacophore  of a known drug, or as an appendage to it. These changes to an existing biologically active compound render the compound light-responsive. Photo-chemically induced structural changes influence the biological activity of the photoresponsive molecules and hence their pharmacodynamics and pharmacokinetic properties.

Appropriate tuning of photochemical properties ideally results in dynamic control of drug-action in confined space and time. Photopharmacology aims at preventing severe side effects and activity of the bioactive compound outside the intended target, thus optimizing/expanding the therapeutic window substantially.

 

Photopharmacology puts traditional pharmacology under control making use of light. Photocontrol can be either extrinsic (external light stimulus) or intrinsic (light from inside the body through e.g. fluorescence activation  at the site of action). Critical factors are: Target-selection, light-delivery, choice of photoresponsive unit (photoswitch) and drug-optimization.

Other definitions may include the use of biocompatible photo-removable drugs and generally light-responsive molecules. It is important, however, to mention that different approaches lead to different levels of control.  Photoswitches  offer the advantage of switching between different states reversibly. Thus allowing for e.g. local activation and deactivation. Also further temporal deactivation can be governed by appropriate choice of thermal stabilities of the active and inactive isomer. Furthermore, different modality selective activity can be achieved in special cases, where the different isomers of the photoswitch show preferences for different pharmacological targets.