https://blogs.scientificamerican.com/observations/new-uses-for-old-medications/

Despite decades of research, diseases of the brain have proven especially difficult to treat. Consider Alzheimer’s disease—every single clinical trial of an Alzheimer’s drug to date has failed. In January Pfizer announced that it had ended research on drugs for the disease, as well as for Parkinson’s. Autism has been similarly frustrating; despite the attention it has received, we still have no effective treatments. Then there’s schizophrenia. It hasn’t seen a breakthrough for more than 60 years, since the discovery of chlorpromazine (better known as Thorazine), which happened largely by chance.

Still, as a neuroscientist who has studied schizophrenia for decades, I am optimistic. The story of chlorpromazine, an antihistamine that was repurposed for schizophrenia, offers a powerful lesson. We now have the ability to find other drugs that could be repurposed to treat brain diseases, thanks to new technologies. Medicines already on our shelves may hold untapped promise for treating brain diseases—if only pharmaceutical companies can be prompted to share their data with scientists.