Nonhuman Primate CNS Assessments of 18F-Insulin After Intranasal Administration

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PROJECT SUMMARY/ABSTRACT Alzheimer's disease (AD) is the leading neurodegenerative disorder presently affecting several million patients in the United States. Since the number of AD patients worldwide is anticipated to significantly escalate over the next decade, there is a critical need to establish effective therapies to alleviate the devastating AD cognitive decline symptoms that are result of pathophysiological changes in AD brain. Vigorous research efforts in many laboratories are focused upon discovering and developing therapies to halt AD pathophysiological changes. Insulin dysregulation is thought to contribute to the pathophysiology of AD, whereby brain insulin resistance is considered to affect not only critical brain insulin receptor signaling cascades but also insulin growth factor 1 (IGF1) levels that together, separately or adjunct to other pathological changes may contribute to cognitive decline AD symptoms. Hence, one therapeutic approach to alleviate cognitive decline symptoms is by the intranasal administration of insulin, which has been recently evaluated in a few early phase clinical trials. The preliminary trials have revealed that in some patient AD groups, cognitive enhancement and/or stability are realized as measured by established clinical cognitive scoring assessments. We hypothesize that post intranasal insulin dosing causes olfactory facilitated brain and/or pulmonary-enteric facilitated CNS insulin uptake mechanisms resulting in differentially elevated brain and CSF insulin levels. We will test this intranasal insulin hypothesis since the literature is devoid of information regarding temporal insulin concentration changes in live primate brain as a function of intranasal insulin dosing and insulin CSF enhancing mechanisms remain ill defined. Our long-term objective is to provide the clinic a viable quantitative PET imaging approach to optimize an intranasal dosed insulin therapy for AD and related patients. The goal of this R21 application is to establish a proof-of-concept (POC) PET imaging platform that will rigorously assess high specific activity (HSA) fluourine-18 (18F) insulin (18F-insulin) dose compositions using intranasal vs. intravenous administration routes in nonhuman primates (NHPs, rhesus monkeys), resulting in metabolite corrected CNS and select peripheral tissue 18F-insulin activity distribution measures vs. time as correlated to cognate tracer blood and CSF temporal profiles. The PET imaging assessments will enable optimization of the intranasal insulin dosing regimen, afford a more detailed understanding of how the insulin tracer gets into brain and peripheral tissues, and will establish a PET imaging based 18F-insulin platform that will be suitable for translation, thereby enabling future clinical PET imaging appraisals of AD patients. The investigation goal will be accomplished with three progressive specific aims and efforts over a twenty-eight month period, as follows: Specific Aim 1: Synthesize high specific activity 18F-insulin, evaluate stabilities of select tracer dose compositions, and utilize selected stable tracer dose forms for the Aim 2 studies; Specific Aim 2: Evaluate the Aim 1 identified HSA 18F-insulin tracer dose forms in rhesus monkeys using a test-retest paradigm to identify optimal intranasal delivery methods, tracer CNS and select peripheral tissue penetration and distribution profiles by quantitative PET imaging determinations coupled to18F-insulin blood and cerebral spinal fluid profiling, as compared to related 18F-insulin intravenous dosed measures; and Specific Aim 3: Confirm the Aim 2 PET imaging paradigm by quantifying 18F-insulin CNS and select peripheral tissue activity distributions over time correlated to tracer profiles in blood and cerebral spinal fluid in age similar male and female monkey cohort groups, thereby defining an optimal quantitative intranasal delivered 18F-insulin PET imaging approach suitable for clinical imaging translation.