Diseases of the central nervous systems (CNS) are a nightmare for big pharma companies. Well, it is not surprising at all that not only companies, but research centers all over the world, apply traditional drug discovery approaches to tackle a disease that does not appear to be target-centered. Antidepressants and mood/behavioral modulators are well-known drugs acting via polypharmacology.
The pathway that should be followed by these entrepreneurs is not yet paved, but high rewards are expected to the ones that will be able to unveil it in a new the drug discovery pipeline. Personalized medicine and polypharmacology/systems biology approaches are the bullets, however it is useless when no target is known. The drug-target relationship is (without any doubt) important to define the biological profile of a compound, despite that it must be emphasized that this relationship is by no means a one-way road. Defining targets is not only a much trickier step towards the main goal (a useful treatment) but it requires a new way of thinking the biological network and how it could be affected in CNS diseases.
http://www.nature.com/news/novartis-to-shut-brain-research-facility-1.9547