First-in-human positron emission tomography study of intranasal insulin in aging and MCI

Intranasal insulin (INI) is being explored to treat Alzheimer's disease and other conditions. The method of intranasal delivery has been shown to affect outcomes, requiring validation prior to clinical investigation. We conducted a first-in-human positron emission tomography (PET) study using a novel radiotracer, [⁶⁸Ga]Ga-NOTA-insulin, administered intranasally with a specialized device (Aptar Cartridge Pump System) to evaluate the kinetics of insulin uptake and distribution in the brain.

[⁶⁸Ga]Ga-NOTA-insulin was intranasally administered (≈ 0.037 ± 0.001 GBq) to adults who were cognitively normal (CN, n = 7) or had mild cognitive impairment (MCI, n = 9). A dynamic 40 minute brain PET scan, followed by a 15 minute whole-body PET/computed tomography scan was acquired. Physiologic parameters were measured at baseline, during, and post-scan. Brain uptake and time-activity curves were determined for fused PET/magnetic resonance imaging images.

Radiochemistry was optimized for producing [⁶⁸Ga]Ga-NOTA-insulin with high radiochemical purity (> 99%) and molar activity (95 GBq/µmol). No safety issues were identified. PMOD analyses showed whole-brain average standard uptake value (SUV;g/mL) ≈ 0.68 ± 0.01; radioactivity in the brain and whole body were undetectable by 40 and 60 minutes post radiotracer administration respectively. Elevated (p < 0.01) SUVs averaged over the 40 minute period after INI administration were observed for 11 regions: olfactory cortex, hippocampus, parahippocampus, amygdala, superior and middle temporal pole, insula, caudate, putamen, thalamus, and anterior cingulum. Time-activity curves showed different uptake patterns for MCI and CN groups. Baseline pulse pressure, plasma insulin, and phosphorylated tau217 correlated with uptake for subgroups based on cognitive status and sex.

[⁶⁸Ga]Ga-NOTA-insulin is a safe and effective PET radiotracer for validating intranasal delivery of insulin to the brain in humans and revealed significant insulin uptake in multiple brain regions. Future studies should incorporate such validation before initiating clinical trials of intranasally administered agents. Further investigation of mechanisms underlying differences in INI uptake among clinical subgroups is also needed.

Intranasal [⁶⁸Ga]Ga-NOTA-insulin is a safe and effective positron emission tomography radiotracer in humans.Intranasal insulin increased brain uptake in multiple regions for all participants.Uptake varied by cognitive status, sex, vascular factors, and amyloid burden.Our protocol provides a method to validate intranasal delivery devices for future trials.