|Alloswitch-1 is the first reported photo-switchable negative allosteric modulator (NAM) for an endogenous G protein-coupled receptor , in this case a NAM of the mGlu5 metabotropic glutamate receptor. Violet light isomerizes the trans molecule to the cis molecule and green light reverses this isomerization . In dark conditions trans-alloswitch-1 antagonizes IP production by quisqualate (orthosteric agonist)-activated mGlu5 receptors. Exposure to violet light reduces this level of antagonism, indicating that the cis-isomer is less active as a NAM than the trans-isomer .
The development of photo-switchable compounds is being pursued by pharmaceutical companies as a method to improve pharmacological selectivity by allowing precise spatio-temporal regulation of drug action.