'Striking' Benefit of Intranasal Insulin in Slowing Dementia

LOS ANGELES — Daily intranasal insulin may be effective in slowing progression of mild cognitive impairment (MCI) or Alzheimer's disease (AD), new research suggests.

Investigators found intranasal insulin administered via a novel delivery device slowed the rate of cognitive decline by 1 to 2 years.

"The magnitude of the benefit is striking," study investigator Suzanne Craft, PhD, professor of gerontology and geriatric medicine at Wake Forest School of Medicine in Winston-Salem, North Carolina, told Medscape Medical News.

"This is the first trial where a medication has been delivered intranasally to treat AD," said Craft.

The findings were presented here at the Alzheimer's Association International Conference (AAIC) 2019.

Protective Effect

Insulin is essential for normal functions in the body and brain. It enhances communication between neurons, increases brain blood flow, and protects against beta-amyloid (Aβ) and abnormal tau.

"One of the things I think is very important for memory is that insulin protects the synapses against amyloid, and also generates new synapses. How well insulin works is the best predictor of how successfully one will age," said Craft.

It appears either patients with AD have low levels of insulin in the brain or the hormone is not working effectively. Boosting insulin levels in the brain might help. However, injecting insulin does not get the hormone straight into the brain, and might lower blood sugar levels, said Craft.

For the study, researchers used a novel mode of delivery — a device that facilitates intranasal applications. The technology involves creating very small aerosol-like droplets of insulin that are driven upwards, directly into the brain and not into the blood stream or lungs, said Craft.

There is growing interest in intranasal delivery of insulin, partly because it is able to penetrate the blood–brain barrier, she said.

The study included 289 patients across 26 sites who had mini-mental state examination (MMSE) scores above 20. Participants were randomly assigned to receive 20 international units (IUs) of insulin or placebo twice daily for 12 months, after which they could opt to receive inulin for 6 months in an open-label phase.

The study began with the Kurve Vianase device, which the researchers had used in all their previous studies. The manufacturer tried to improve the device for this trial, "but unfortunately that improvement resulted in unreliability of that device," said Craft.

She explained that the manufacturer put a new timer switch on the device that "worked erratically," meaning study participants "kept having to replace" the device.

The study then switched to a second delivery system, the Impel Precision Olfactory Device. This meant 49 study subjects were assessed with the first device and 240 with the second device.

There were no safety issues with either device, and there was "respectable compliance" for both, said Craft.

Clinically Significant

The primary outcome was Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), with higher scores indicating worse outcomes. Researchers administered other cognitive and behavioral tests and measured abnormal amyloid and tau proteins — ratios of Aβ42/Aβ40 and Aβ42/tau — in cerebrospinal fluid (CSF) samples.

"These ratios provide an integrated measure of Alzheimer's pathology and have been found to be better predictors than individual biomarkers in some studies," noted Craft.

In the analysis of patients using the second device, both groups worsened cognitively. "So there was no benefit" from the intranasal insulin in either the 12-month trial or this open-label phase, said Craft.

Also in this group, there were no differences between those receiving placebo and those getting insulin in any other measures that researchers incorporated into the study.

However, it was "a different picture" with the first device, said Craft. Here, the insulin group showed an advantage over 12 months, and by 18 months, that group had a 6-point advantage on the ADAS-Cog compared with those who were originally assigned to placebo (P = .018).

"This is a clinically significant effect," said Craft. "We estimate it to be a 1-to-2 year slowing in the rate of disease progression."

Adults with AD typically worsen by about 3 ADAS-Cog points per year, noted Craft.

The Earlier, the Better?

In addition, the CSF biomarker ratios improved with the insulin group using the first device, suggesting a slowing of brain injury associated with AD.

"This showed us that we were affecting the proteins and pathology that is part of Alzheimer's disease, in addition to the cognitive symptoms," said Craft.

It is possible the cognitive benefits will increase as more time passes, she added.

The researchers tested the ability of the first device to deliver insulin into the brain. They did so by administering saline and insulin at different times, each followed by a lumbar puncture to assess CSF levels.

"The data are showing that insulin levels were elevated with insulin treatment by that device at every occasion. That was significant; it showed that the device was getting insulin into the brain," said Craft.

The investigators are conducting further analyses to determine whether cognitive worsening of those with higher MMSE scores at baseline slowed more than in participants with lower baseline scores.

"We can't say that's the case yet, but that's what we are thinking is going on — that the earlier you get the insulin, the better," she said.

It's not clear why the two devices produced different results. Craft noted that devices may differ in their ability to deliver insulin to the brain. "All devices are not created equal," she noted.

A phase 3 trial is being planned to confirm the beneficial effects of intranasal insulin in patients with MCI and AD. It is not yet clear which device will be selected for this next study although "we will validate the device prior to the beginning of the study," said Craft.

Potential New Mechanism

Commenting on these findings for Medscape Medical News, Rebecca Edelmayer, PhD, director of scientific engagement for the Alzheimer's Association, said the study is "an example of how we're diversifying the clinical trial pipeline with new ideas, of how we are sort of thinking outside the box."

Intranasal insulin may represent a potential new mechanism for treating AD, she said.

"Any type of treatment, whether it be a medicine or a lifestyle intervention, that's going to delay the onset or slow the progression of the disease would be a win for this disease field."

The Alzheimer's Association "wants to continue to make sure" that promising treatments undergo "a rigorous clinical trial," which will be "the next step" for intranasal insulin, said Edelmayer.

Study funding was provided by National Institute on Aging (NIA). Eli Lilly provided placebo for the trial blinded phase, and Humulin-R U100 for the open label extension. Craft and Edelmayer have disclosed no relevant financial relationships.

Alzheimer's Association International Conference (AAIC) 2019: Abstract 35542. Presented July 17, 2019.

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