Background: Two recent randomized, placebo-controlled trials of putative disease-modifying agents (davunetide, tideglusib) in progressive supranuclear palsy (PSP) failed to show efficacy, but generated data relevant for future trials. Methods: We provide sample size calculations based on data collected in 187 PSP patients assigned to placebo in these trials. A placebo effect was calculated. Results: The total PSP-Rating Scale required the least number of patients per group (N=51) to detect a 50% change in the 1-year progression and 39 when including patients with ≤ 5 years disease duration. The Schwab and England Activities of Daily Living required 70 patients per group and was highly correlated with the PSP-Rating Scale. A placebo effect was not detected in these scales. Conclusions: We propose the 1-year PSP-Rating Scale score change as the single primary readout in clinical neuroprotective or disease-modifying trials. The Schwab and England Activities of Daily Living could be used as a secondary outcome.

Original languageEnglish
Pages (from-to)742-747
Number of pages6
JournalMovement Disorders
Issue number5
StatePublished - 1 May 2016


FundersFunder number
National Institute on Alcohol Abuse and AlcoholismR21AA020356
National Institute on AgingR01AG038791
National Institute of Neurological Disorders and StrokeU54NS092089


    • Clinical trials
    • Placebo effect
    • Power calculation
    • Progressive supranuclear palsy
    • Rate of progression


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