PSP Trial Platform enrols first participant in multi-drug study

The PSP Trial Platform (PTP) has enroled its first participant, marking the operational start of what is described as the most ambitious collaborative trial effort yet mounted for progressive supranuclear palsy. The platform is led by the University of California, San Francisco (UCSF) and funded by a five-year grant of up to $75.4 million from the National Institute on Aging.

PSP is a rare and uniformly fatal neurodegenerative disorder affecting balance, movement and cognition. It is frequently misdiagnosed as Parkinson's disease in its early stages, and there is currently no approved treatment. The disease affects an estimated 20,000 people in the United States at any given time, and the relatively small patient population has historically made trial recruitment difficult and slowed drug development.

How the platform works

The PTP is modelled on the HEALY ALS Platform Trial, which has shown that a master-protocol design can test multiple experimental agents simultaneously while sharing a common infrastructure and control arm. The PTP intends to enrol 440 participants over two years across 50 clinical sites nationwide. New drugs can be added to the platform as they become available without requiring a new trial to be initiated from scratch.

Critically, the trial has been designed so that 75% of participants receive an active investigational drug during the first year, with all participants receiving an active drug thereafter. This departure from conventional placebo-controlled design is intended to make enrolment more attractive to patients and carers in a condition with no existing treatment options.

Two drugs are already active in the platform: LM11A-31, a neurotrophin-pathway modulator developed by PharmatrophiX that targets multiple tau-related neurodegenerative mechanisms, and AADvac1, an active tau immunotherapy developed by Axon Neuroscience based on more than two decades of research into tau protein pathology.

Adam Boxer, Endowed Professor in Memory and Aging at UCSF and lead principal investigator, said the trial is expected to "rapidly accelerate efforts to identify effective PSP therapies by increasing the number of promising drugs tested, while expanding access to potential treatments to more patients."

Market and regulatory context

The platform approach reflects a broader shift in rare neurodegenerative disease research toward adaptive, multi-arm designs that regulators in both the US and Europe have signalled they are willing to accommodate. The FDA's Complex Innovative Trial Designs programme, active since 2018, provides a pathway for sponsors to seek early engagement on non-traditional trial architectures of exactly this type, and the HEALY precedent has already generated regulatory familiarity with the model in ALS.

For companies such as PharmatrophiX and Axon Neuroscience, participation in an externally funded platform trial offers a cost-efficient route to Phase 2 data in a high-unmet-need indication. Both candidates are at an early clinical stage, and neither company has a product on the market. Positive data from either arm would represent a significant de-risking event and could attract larger pharma partnership interest. The longitudinal biomarker dataset the PTP is expected to generate may prove as commercially valuable as any individual efficacy readout, given how poorly understood PSP pathophysiology remains.

The PTP is open to individuals with Richardson's syndrome who have experienced progressive symptoms for fewer than five years and are accompanied by a care partner. Further information is available via ClinicalTrials.gov under identifier NCT07173803.