The Progressive Supranuclear Palsy Clinical Trial Platform (PTP)

PROJECT SUMMARY / ABSTRACT

Progressive Supranuclear Palsy (PSP) is a severe neurodegenerative disease of aging that usually leads to

death within 5-7 years of diagnosis. There are no effective treatments for PSP, but therapeutic approaches being

tested in clinical trials for other neurodegenerative diseases, such as Alzheimer’s (AD) and amyotrophic lateral

sclerosis may be even more promising for PSP. Despite excellent feasibility of large multicenter PSP clinical

trials, there are few new studies, limiting options for patients to access experimental therapies and severely

delaying the identification of effective treatments. New, efficient clinical PSP trial programs and focused efforts

to identify PSP biomarkers are urgently needed. The overarching goal of the PSP Trial Platform (PTP) is to

conduct a randomized, placebo-controlled, Phase 2 platform trial in mild-moderate PSP that will simultaneously

test at least three different tau-related or neuroprotective therapies to determine safety, tolerability and clinical

proof of concept based on a multimodal clinical rating scale, the modified PSP Rating Scale-15 (mPSPRS-15).

Platform trials create economies of scale through generation of a common clinical trial protocol and the ability to

share placebo group information to allow a greater number of therapies to be tested in a shorter amount of time

and with less expense than multiple independent clinical trials. Three therapies will be compared for 12 months,

in four parallel arms, with a 3:1 (drug:placebo) randomization ratio to encourage recruitment, followed by an

optional, 12-month open-label extension. Key inclusion criteria will be a diagnosis of mild-moderate PSP, with

symptoms < 5 years in duration, preserved ability to ambulate with minimal cognitive impairment (Mini Mental

State Exam > 25). All individuals will be screened with a validated MRI diagnostic tool to rule out non-PSP

etiologies. Using these criteria, we estimate that 110 participants per group (3 drug, 1 placebo) will be necessary

to have 80% power to detect a 33% slowing in decline on the mPSPRS-15 over 12 months, accounting for 20%

attrition. Key secondary endpoints will include including changes in the total PSPRS, activities of daily living

(Schwab and England ADL), global status (Clinical Global Impression of disease severity), the PSP Quality of

Life scale, a newly validated PSP Cognitive Composite, and volumetric MRI biomarkers including midbrain

volume. Exploratory CSF biomarker discovery efforts will focus on changes in PSP-associated tau fragments,

axon guidance network proteins, and lysosomal proteins and lipids over 12 months. Leveraging the experience

and resources of the CurePSP Centers of Care, the Parkinson’s Study Group, the NIH-funded ALLFTD research

network, and the NIH AD Clinical Trials Consortium (ACTC), we propose to enroll 440 participants at ~50 sites

in North America over 24 months. Like other platform trials, additional therapeutic arms may be added after initial

program launch. If successful, the PTP will provide key data for decision-making about which therapies to pursue

in larger efficacy trials, create a new infrastructure to efficiently evaluate PSP therapies, and a new resource for

longitudinal PSP clinical and biomarker data, and biosamples, to be shared with other researchers.