Montelukast acts to reduce inflammation in the lungs, and this led to the idea that it might reduce brain inflammation. This led to a successful study in rats, as reported below in four media articles, and the original research article.
Old rat brains rejuvenated and new neurons grown by asthma drug
Asthma drug could rejuvenate ageing brains, study suggests
Dementia cure? Scientists find common asthma drug REJUVENATES ageing brains
Asthma drug Singulair may be a cure for Alzheimer’s, claims study
Original rat brains research article:
Structural and functional rejuvenation of the aged brain by an approved anti-asthmatic drug
Because montelukast has long been approved for human use (for asthma), this led quickly to a successful Phase 1 clinical trial:
…Successful Clinical Study for Montelukast for the Treatment of Degenerative Diseases of the Brain
And this has been followed by the recent start of a Phase 2A clinical trial:
…Initiates Phase 2A Montelukast Versafilm™ Clinical Trial in Alzheimer’s Patients
The outcome of the Phase 2A will give the first indications of whether montelukast actually will have effects on human brains. Many drugs have previously appeared promising in rat studies, but did not turn out to have beneficial effects for humans, and never made it to human use. Even those approved for humans don’t have much beneficial effect, if any: The hard truth about Alzheimer’s drugs.
All the links here have been added to Alzheimers > Treatment > Drugs.