The NADAPT Study: a Randomized Double-blind Trial of NAD Replenishment Therapy for Atypical Parkinsonism

Background/Rationale: Atypical parkinsonian syndromes (APS) are rapidly progressive, debilitating, and incurable neurodegenerative diseases, including progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and corticobasal syndrome (CBS). These are classified as rare and orphan disorders according to EU regulation, with a reported prevalence of 7/100,000 for PSP, 4.4/100,000 for MSA, and 0.6-1/100,000 for CBS, although accurate numbers for CBS are lacking. Currently, there are no neuroprotective therapies able to delay the progression of APS. Moreover, unlike Parkinson's disease (PD), symptomatic therapy is largely ineffective. Without options for disease modification or symptom relief, patients succumb to rapidly increasing motor and cognitive disability, and become quickly care-dependent, with an estimated overall survival from diagnosis between 3-8 years for PSP, 6-10 years for MSA and \~7 years for CBS. Despite being a source of morbidity and mortality comparable to amyotrophic lateral sclerosis (ALS), there are currently no clinical treatment studies on PSP, MSA, or CBS in Norway, and very few initiatives globally. Given the complete lack of therapy - neuroprotective, symptomatic or palliative - these disorders constitute an important and urgent challenge to health care and society. Taken together, the findings of our NAD-replenishment trials, NADPARK (NCT03816020) and NR-SAFE (NCT05344404), provide robust experimental evidence that: 1) NR has a dose-dependent symptomatic antiparkinsonistic effect, which occurs on the top of optimal dopaminergic therapy; 2) Nominate NR as a potential neuroprotective therapy for parkinsonism, able to ameliorate cerebral metabolism and dampen neuroinflammation. Encouraged by these findings, the investigators proposed that NAD-replenishment therapy via oral NR intake could show promise as both symptomatic and neuroprotective therapy for APS. Given the complete lack of treatment options for individuals with PSP, this trial is both timely and necessary. The investigators will conduct the NADAPT trial, a randomized, double blinded, phase II trial testing the efficacy of NAD replenishment therapy with nicotinamide riboside (NR) as a disease modifying therapy for APS. 130 patients with PSP, 165 patients with MSA, and an undetermined number of patients with CBS will be stratified by disease and randomized 1:1 per disease to receive either 3000mg NR a day or placebo (Fig 1). Follow up will be 18 months and consist of both in-clinic visits and decentralized patient-reported outcomes. NADAPT follows a basket trial design, essentially encompassing three trials in one, and drawing added value from the parallel enrolment and follow up.