Intranasal Delivery of Metabolically Resilient Glutathione: <i>In Vivo</i> Pharmacokinetic, Permeation, and Efficacy Studies

Nose-to-brain delivery is an attractive drug delivery strategy for the treatment of Alzheimer's disease (AD) as it offers direct penetration of drugs into the brain by surpassing the blood-brain barrier, while reducing the potential systemic side effects. We developed a glutathione analogue, ψ-GSH, that resists catabolism and reduces AD-related behavioral and pathological abnormalities <i>in vivo</i>. Although ψ-GSH is effective via intraperitoneal administration, limited oral availability hinders the clinical translation of ψ-GSH. In this study, we sought to evaluate if intranasal ψ-GSH administration can provide neuroprotection in an acute mouse model of AD-related pathology. The pharmacokinetic analysis confirmed brain delivery of the compound to levels 4-fold higher than those achieved by an efficacious systemic dose of ψ-GSH. Unaffected stability in simulated nasal fluid and mucosa further displayed the feasibility of this delivery method. Repeated intranasal administration of ψ-GSH prevented cognitive impairment induced by the intracerebroventricular injection of Aβ_1-42 without significant adverse effects. Biochemical and immunohistochemical analyses displayed the beneficial effect of the treatment on oxidative stress and inflammatory markers by engaging GSH-dependent mechanisms, mirroring the pharmacological effects of intraperitoneal ψ-GSH. Additionally, <i>in vitro</i> directional transport studies using a human nasal epithelial cell line showed directional brain transport of ψ-GSH, without compromising the integrity of tight junction proteins. Collectively, our results demonstrate intranasal delivery as a safe and effective alternative for brain delivery of ψ-GSH at pharmacologically relevant concentrations for the treatment of neurological conditions. The study supports future formulation studies for intranasal ψ-GSH administration and its efficacy evaluation in transgenic AD mouse models for preclinical advancement.