Introduction: Treatments for Alzheimer's disease (AD) are needed due to the growing number of individuals with preclinical, prodromal, and dementia forms of AD. Drug development for AD therapies can be examined by inspecting the drug development pipeline as represented on clinicaltrials.gov.

Methods: Clinicaltrials.gov was assessed as of January 30, 2018 to determine AD therapies represented in phase I, phase II, and phase III.

Results: There are 112 agents in the current AD treatment pipeline. There are 26 agents in 35 trials in phase III, 63 agents in 75 trials in phase II, and 23 agents in 25 trials in phase I. A review of the mechanisms of actions of the agents in the pipeline shows that 63% are disease-modifying therapies, 22% are symptomatic cognitive enhancers, and 12% are symptomatic agents addressing neuropsychiatric and behavioral changes. Trials in phase III are larger and longer than phase II or phase I trials, particularly those involving disease-modifying agents. Comparison with the 2017 pipeline shows that there are four new agents in phase III, 14 in phase II, and eight in phase I. Inspection of the use of biomarkers as revealed on clinicaltrials.gov shows that amyloid biomarkers are used as entry criterion in 14 phase III disease-modifying agent trials and 17 disease-modifying agent trials in phase II. Twenty-one trials of disease-modifying agents in phase II did not require biomarker confirmation for AD at trial entry.

Discussion: The AD drug development pipeline is slightly larger in 2018 than in 2017. Trials increasingly include preclinical and prodromal populations. There is an increase in nonamyloid mechanisms of action for drugs in earlier phases of drug development. Biomarkers are increasingly used in AD drug development but are not used uniformly for AD diagnosis confirmation.