BACKGROUND: Individuals with Down syndrome are likely to develop clinical and neuropathological brain changes resembling Alzheimer's disease dementia by the ages of 35-40 years. Intranasal insulin is a potential treatment for neurodegenerative disease that has been shown to reduce amyloid plaque burden and improve verbal memory performance in normal as well as memory-impaired adults. Investigations have shown that rapid-acting insulins may result in superior cognitive benefits compared with regular insulin. OBJECTIVES: The primary objective of this study was to measure the safety and feasibility of intranasal rapid-acting glulisine in subjects with Down syndrome. Secondarily, we estimated the effects of intranasal glulisine on cognition and memory in Down syndrome. METHODS: A single-center, single-dose, randomized, double-blind, placebo-controlled, cross-over pilot study was performed to test the safety of intranasal glulisine vs placebo in 12 subjects with Down syndrome aged >/= 35 years. Intranasal administration utilized the Impel NeuroPharma I109 Precision Olfactory Delivery (POD((R))) device. The primary outcomes were the occurrence of any or related adverse and serious adverse events. Secondary post-treatment cognitive outcome measures included performance on the Fuld Object-Memory Evaluation and Rivermead Behavioral Memory Test. RESULTS: Intranasal glulisine was safe and well tolerated in the Down syndrome population. No adverse or serious adverse events were observed. CONCLUSIONS: Further investigations are necessary to better evaluate the potential cognitive-enhancing role of intranasal insulin in the Down syndrome population. CLINICALTRIALS. GOV ID: NCT02432716.