Device type critical
These effects persisted in the open-label analyses. Patients who received intranasal insulin had superior ADAS-cog-12 scores at month 15 (−5.70 points; 95% CI, −9.62 to −1.79 points; P = .004) and month 18 (−5.78 points; 95% CI, −10.55 to −1.01 points; P = .02), compared with their counterparts who received insulin via the second device. This part of the study also showed that, although individual biomarkers did not differ significantly between the two arms, the ratios of A-beta42 to A-beta40 (P = .01) and A-beta42 to total tau (P = .03) increased with use of the first device. The number, type, and severity of adverse events were comparable between the insulin and placebo groups in this arm of the study.
The mixed results revealed by the trial demonstrate that the device used for intranasal insulin administration is paramount in determining the therapy’s potential efficacy. “Our take-home message is that the device is a very important factor for these studies and that one needs to validate their ability to effectively deliver insulin to the CNS,” said Dr. Craft.
“We were quite confident that the first device was able to do that. On the other hand, the second device has never been tested in that way, and we still don’t know whether or not that device was able to successfully deliver insulin,” she said.
The investigators recognize the need for more research in the field. Such studies, Dr. Craft noted, will utilize administration devices that have been previously verified to have the ability to deliver insulin to the central nervous system. “We’re currently testing several devices,” she noted. “We’re using a protocol where we administer insulin with the devices and then conduct a lumbar puncture about 30 minutes later to verify that it is actually raising insulin levels in the cerebrospinal fluid.”
Not a failure
Commenting on the findings, Samuel E. Gandy, MD, PhD, who was not involved in the study, said the research illustrates the challenge when a new therapy, a new delivery device, and a cohort of cognitively impaired patients collide. “The result is not quite a slam dunk but is also by no means a failure,” commented Dr. Gandy, Mount Sinai Chair in Alzheimer’s Research at Mount Sinai Medical Center, New York.
“One looks forward to future iterations of the Craft et al. approach, wherein the trialists tweak the ligand and/or the delivery schedule and/or the device and/or the disease and/or the disease stage,” Dr. Gandy added. “Another ligand, VGF, also holds promise for intranasal delivery, based on work from Steve Salton, Michelle Ehrlich, and Eric Schadt, all from Mount Sinai. Perhaps the nose knows!”
For Dr. Craft, the potential upside of intranasal insulin for these patients is significant and warrants further investigation. “I understand why people who are not familiar with prior research in this area might be skeptical of our enthusiasm, given the results in the intention-to-treat population,” she said. “But those of us who have been working along with this for a while now, we feel like we’ve got to do the next study. But we need to have a device that we know works,” Dr. Craft added.
“If this is real, then there may be a very large clinical benefit in symptomatic patients, and there’s nothing so far that has really improved symptomatic disease.”
The study was supported by the National Institute on Aging. Eli Lilly provided diluent placebo for the blinded phase and insulin for the open-label phase of the clinical trial at no cost. Dr. Craft received grants from the National Institute on Aging and nonfinancial support from Eli Lilly during the conduct of the study and personal fees from T3D Therapeutics and vTv Therapeutics outside the submitted work.
A version of this article originally appeared on Medscape.com.