The most common reason behind dementia is Alzheimer’s disease (AD) and it is predicted
to be the third life-threatening disease apart from stroke and cancer for the geriatric population.
Till now, only four drugs are available on the market for symptomatic relief. The complex
nature of disease pathophysiology and lack of concrete evidence of molecular targets are the major
hurdles for developing a new drug to treat AD. The rate of attrition of many advanced drugs at
clinical stages makes the de novo discovery process very expensive. Alternatively, Drug Repurposing
(DR) is an attractive tool to develop drugs for AD in a less tedious and economic way. Therefore,
continuous efforts are being made to develop a new drug for AD by repurposing old drugs
through screening and data mining. For example, the survey in the drug pipeline for Phase III clinical
trials (till February 2019) consists of 27 candidates, and around half of the number are drugs
which have already been approved for other indications.
Although in the past, the drug repurposing process for AD has been reviewed in the context of disease
areas, molecular targets, there is no systematic review of repurposed drugs for AD from the
recent drug development pipeline (2019-2020). In this manuscript, we have reviewed the clinical
candidates for AD with emphasis on their development history, including molecular targets and the
relevance of the target for AD.