An analysis of clinical trials shows that the pipeline for potential treatments of Alzheimer's disease (AD) is small and rate of success is limited, according to research published in the open access journal Alzheimer's Research & Therapy.

Researchers at the Cleveland Clinic Lou Ruvo Center for Brain Health have examined clinicaltrials.gov - the largest clinical trials database - for all ongoing studies for Alzheimer's disease (AD) from the years 2002 to 2012. They found an urgent need to increase the number of agents entering the AD drug development pipeline and progressing successfully towards new therapy treatments.

The main findings of the study conclude that there are relatively few drugs in development for Alzheimer's disease; the failure rate for AD drug development is 99.6% for the decade 2002-2012; and the number of drugs has been declining since 2009.

Jeffrey Cummings, lead researcher from Cleveland Clinic Lou Ruvo Center for Brain Health, says: "Our goal was to examine historical trends to help understand why Alzheimer's disease treatment development efforts so often fail. With an estimated 44 million people living with the condition, the study shows that the Alzheimer's disease drug development ecosystem needs more support given the magnitude of the problem."

This comprehensive analysis illustrates the high rate of failure of compounds and the need for a constant supply of new drugs or a higher focus on repurposing studies is needed. Repurposing studies involve taking an existing approved drug and studying it in a new use or condition to see if current treatments could be used in new ways. With AD more expensive to the US economy than cardiovascular disease or cancer, researchers believe the system of AD drugs must be supported, grown and coordinated to improve the success rate and development of new AD therapies.

Kate Zhong, another researcher on the study, says: "By analyzing both completed as well as on-going trials and currently active compounds, we were able to provide insight into longitudinal trends in drug development. What we found was that the investment in AD drugs and therapies is relatively low compared to the challenge posed by the disease. The pipeline is almost dry."