What Is Photopharmacology?

 

Photopharmacology is an emerging approach in medicine, in which drugs are activated and deactivated with light. Light  carries energy that can be used to change the three-dimensional structure of the drug molecule. As the effect of the drug on the body depends on its three-dimensional structure, changing this structure leads to the regulation of the activity of the drug in the body. Ideally, a photopharmacological drug would be administered in its inactive form and then can be activated reversibly  at its target.

 

 

Why Is It Important?

 

 

Drugs efficiently alleviate symptoms and cure diseases. However, drugs are not always as selective  as one would wish for. This poses a problem both for existing drugs and clinical research. Selectivity in this context means that the drug only acts on a certain defined target (e.g. the origin of headache) and not on any other targets (e.g. stomach). The sometimes occurring side-effects  observed in commercial drugs (as nausea, etc.) stem from such small problems of drug selectivity. More severe, but fortunately less common, are toxic side-effects.

 

 

How Does It Work?

 

 

Photopharmacology relies on incorporating photoswitches  into the drug-molecules. Ideally a biological target for the drug should fulfill certain photodruggability  criteria. In photopharmacology, existing drugs or drug-candidates are modified with a photoswitch to render them photoswitchable. It is almost impossible to predict the biological activity of a certain modified drug. Thus, usually structure-activity relationship  studies (SAR-studies) of both isomers for different positions of incorporation of the photoswitch are required.

 

 

What Is the Potential?

 

 

Photopharmacology is still an area of fundamental research. It remains to be seen if it will ever make it to clinical applications. Photocontrol in clinical setting, however, is already used for photodynamic therapy.

In view of the recent development and potential of optogenetics , photopharmacology offers a means to achieve similar effects (photocontrol of certain neuronal/body functions) without the need for genetic manipulation of organisms or cells. It might thus be much better suited to succeed in human applications, as it can build on decades of clinical experiences with small molecule drugs and the insights gained in light-delivery from photodynamic therapy (PDT) and optogenetics.