Testing add-on treatments given through the nose

Key Inclusion Criteria: * Documented clinical diagnosis of idiopathic PD * Able to administer study drug or have a caregiver throughout the duration of the study to help administer drug * Willing to continue diet, exercise and medications reported at baseline consistently throughout participation in the trial. Essential changes are permitted * If taking PD medications or any nutraceuticals, must be on a stable dose for at least 30 days prior to Screening Visit. Essential changes will be permitted. * If subject is taking chronic antidepressant or an anxiolytic, must be on a stable dose for at least 90 days prior to Screening. Essential changes will be permitted. Key Exclusion Criteria: * Clinical diagnosis of Type 1 or Type 2 Diabetes Mellitus * Glycated hemoglobin (HbA1c) level ≥ 6.5% * History of symptomatic hypoglycemia and/or documented plasma glucose levels of ≤ 50 mg/dL with symptoms of hypoglycemia. * Mini-Mental State Exam (MMSE) score of ≤ 24 at Screening * Positive COVID-19 test at Screening and/or within 30 days of Screening * Change in or escalation of dose of a chronic therapeutic agent that has the potential to impair cognitive functioning per investigator within the last 8 weeks of Screening or during the study conduct. * Chronic inflammation of nasal cavity, history of recurrent epistaxis, and/or clinically significant medical history of uncontrolled allergic rhinitis, rhino-conjunctivitis, or house dust mite allergy at Screening that may prevent absorption of study treatments. * Insufficiently controlled respiratory disease (i.e., asthma, COPD). * History of any significant neurologic or psychiatric disease other than PD * Current diagnosis of epilepsy and had a history of seizures as an adult within 1 year of Screening, or unexplained recent loss of consciousness, or history of significant head trauma with loss of consciousness * History of non-lacunar ischemic and/or hemorrhagic stroke with residual neurologic deficits. * Unstable or uncontrolled cardiac disease that could expose the subject to additional safety risks * Use of the following medications: Insulin or any other anti-hyperglycemic agent(s) except if used during isolated gestational diabetes, Supplementation with GSH or any medication shown to increase glutathione