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Progressive Supranuclear Palsy

Recent research efforts aimed at curing Progressive Supranuclear Palsy.

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Progressive Supranuclear Palsy

Overview

Progressive supranuclear palsy (PSP) is a rare, fatal neurodegenerative disorder in which abnormal forms of the protein tau—especially “4-repeat tau”—accumulate in brain cells and supporting cells. It commonly causes early backward falls, stiffness and slowed movement, difficulty moving the eyes vertically, speech and swallowing problems, and changes in thinking or behavior; its symptoms can resemble Parkinson’s disease but usually progress more quickly. NINDS PSP overview (ninds.nih.gov)

PSP usually affects adults later in life and has variable clinical forms. In a recent cohort, median survival from symptom onset was 6.4 years, with the common Richardson syndrome form associated with earlier severe swallowing difficulty, need for walking aids, and poorer survival than several variant forms. Clinical prognostic factors in PSP (pubmed.ncbi.nlm.nih.gov) There is no approved treatment that stops or reverses PSP. Current care is multidisciplinary and symptom-focused: selected patients may receive a limited trial of levodopa for stiffness or slowness, while physical, occupational, speech, and swallowing therapy, fall prevention, vision aids, nutrition support, and caregiver planning are central to care. NINDS PSP overview (ninds.nih.gov)

Scope of Recent Research (2020–present)

Research activity has increased meaningfully since 2020, with the field concentrating on whether tau can be reduced, neutralized, stabilized, or cleared; whether lysosomal, inflammatory, synaptic, and mitochondrial damage can be slowed; and whether better biomarkers can identify patients early enough to show a treatment effect. Biomarkers of PSP progression (pmc.ncbi.nlm.nih.gov) The community is not yet close to a proven curative therapy: no disease-modifying treatment has demonstrated clinical efficacy in PSP, but a new NIH-supported platform trial and a Phase 3 tau-lowering RNA therapy represent a substantially more active development pipeline than existed earlier in the decade. PSP Trial Platform award (taggs.hhs.gov) NIO752 Phase 3 study (novartis.com)

Major Breakthroughs and Emerging Therapies

The most advanced direct tau-lowering strategy is NIO752, an antisense oligonucleotide (ASO): a short synthetic RNA-like medicine delivered into cerebrospinal fluid that is designed to reduce production of tau by blocking translation of MAPT messenger RNA. NIO752 Phase I results and Phase III design (pmc.ncbi.nlm.nih.gov) Novartis began a 300-participant, randomized Phase 3 trial in June 2026 for people with mild-to-moderate PSP-Richardson syndrome; participants receive NIO752 or placebo before an open-label extension. NIO752 Phase 3 study (novartis.com) This is an important test of whether lowering tau production can alter the disease course, but it is investigational and has not yet reported efficacy results. NIO752 Phase 3 study (novartis.com)

A second strategy is tau immunotherapy, which attempts to prevent pathological tau from aggregating or spreading between cells. Bepranemab, an intravenous monoclonal antibody targeting the middle region of tau, completed a small Phase 1b PSP trial: 25 participants were enrolled, the drug had an acceptable safety profile, and free tau in cerebrospinal fluid fell by a mean of 80.41%, showing strong target engagement rather than proof of clinical benefit. Bepranemab Phase 1b trial (pubmed.ncbi.nlm.nih.gov) The active tau vaccine AADvac1 has also entered the new PSP Trial Platform; it is intended to prompt the immune system to generate antibodies against abnormal tau. PSP Trial Platform enrollment (psp.org)

Small-molecule approaches aim to make neurons more resilient or alter tau biology indirectly. FNP-223 is an oral inhibitor of O-GlcNAcase, an enzyme involved in removing a sugar modification from proteins; inhibiting it is intended to increase tau O-GlcNAcylation and reduce harmful tau phosphorylation and aggregation. FNP-223 mechanism (ferrer.com) Its placebo-controlled Phase 2 PROSPER trial is evaluating whether this approach can slow PSP progression. FNP-223 Phase 2 trial (clinicaltrials.gov) AZP2006 (ezeprogind) is an oral, multi-target small molecule intended to improve lysosomal function—the cell’s waste-disposal system—while modulating progranulin, tau-related pathology, and neuroinflammation. AZP2006 Phase 2a trial (pubmed.ncbi.nlm.nih.gov)

AZP2006 generated one of the few recent clinical signals in PSP, although it remains preliminary. In a 12-week Phase 2a randomized study of 36 participants, the medicine was acceptably tolerated with no treatment-related serious adverse events; pharmacodynamic findings supported brain exposure and target engagement, while clinical and biomarker trends favored slower progression but were not definitive efficacy evidence. AZP2006 Phase 2a trial (pubmed.ncbi.nlm.nih.gov) The key conceptual shift is that PSP research is no longer limited to attacking tau aggregates alone: current programs pair tau-directed approaches with efforts to protect synapses, improve lysosomal clearance, reduce inflammation, and preserve vulnerable neurons. PSP Trial Platform award (taggs.hhs.gov)

Clinical Trials and Experimental Approaches

The major infrastructure development is the Progressive Supranuclear Palsy Clinical Trial Platform (PTP; NCT07173803), led by Adam Boxer, MD, PhD, at the University of California, San Francisco, with collaborators at the University of California, San Diego, Massachusetts General Hospital, the Alzheimer’s Therapeutic Research Institute, CurePSP, and approximately 50 North American sites. PSP Trial Platform registry record (clinicaltrials.gov) On August 7, 2026, the platform enrolled its first participant. It is designed to test multiple treatments under one shared protocol, initially including AADvac1 and the synapse-protective p75 neurotrophin receptor modulator LM11A-31, while allowing new regimens to be added over time. PSP Trial Platform enrollment (psp.org)

The PTP plans to enroll 440 people with mild-to-moderate PSP across approximately 50 sites and uses a shared placebo group, with a 3:1 active-drug-to-placebo randomization intended to reduce placebo exposure. Its primary goal is efficient Phase 2 proof-of-concept testing, not confirmation of a cure. PSP Trial Platform award (taggs.hhs.gov) Alongside the PTP, Novartis’s Phase 3 NIO752 study is recruiting 300 participants, and the FNP-223 PROSPER study remains a notable Phase 2 oral tau-modifying program. NIO752 Phase 3 study (novartis.com) FNP-223 Phase 2 trial (clinicaltrials.gov)

Methodologies and Scientific Approaches

PSP investigators combine conventional randomized clinical trials with biomarker-rich designs. These include standardized clinical scales such as the Progressive Supranuclear Palsy Rating Scale, structural MRI measures such as midbrain volume, cerebrospinal-fluid tau fragments, neurofilament light chain as an indicator of axonal injury, blood markers, digital assessments, and cognitive measures. Biomarkers of PSP progression (pmc.ncbi.nlm.nih.gov) The PTP also collects imaging and biological samples to identify biomarkers that can show whether a treatment is reaching its target before clinical change is apparent. PSP Trial Platform award (taggs.hhs.gov)

Laboratory research increasingly uses patient-derived induced pluripotent stem cells and three-dimensional midbrain organoids—miniature laboratory-grown tissues—to model sporadic PSP. A 2025 study found that PSP-derived midbrain organoids reproduced progressive loss of tissue size, cell-death signals, reactive glial changes, and accumulation of 4-repeat and phosphorylated tau, providing a more disease-relevant system for testing drugs and discovering targets. PSP midbrain organoid model (pubmed.ncbi.nlm.nih.gov)

Leading Institutions and Funding

UCSF is the central coordinating institution for the PTP, working with UC San Diego, Massachusetts General Hospital, the Alzheimer’s Clinical Trials Consortium, the Parkinson’s Study Group, CurePSP Centers of Care, and industry partners including Axon Neuroscience and PharmatrophiX. PSP Trial Platform registry record (clinicaltrials.gov) The U.S. National Institute on Aging awarded the PTP grant R01AG085029; federal records show $30.28 million awarded through fiscal year 2025, while the PTP announcement describes a five-year award of up to $75.4 million. PSP Trial Platform award (taggs.hhs.gov) PSP Trial Platform enrollment (psp.org)

CurePSP and the Rainwater Charitable Foundation are also expanding the early-stage research pipeline. In July 2026, CurePSP announced its largest Pathway and Pipeline grant cycle to date, including a $300,000 Rainwater Charitable Foundation contribution and projects spanning spatial transcriptomics, artificial-intelligence-assisted therapeutic design, computer-vision biomarkers, and genetic-risk research at institutions including Yale, UCLA, Mayo Clinic, Cambridge, UT Southwestern, LMU, and University College London. CurePSP 2026 research grants (psp.org)

Strengths, Limitations, and Challenges

The field’s strengths are an increasingly precise biological focus on tau, the arrival of RNA-lowering and active-vaccine approaches, more useful patient-derived disease models, and the PTP’s ability to test therapies faster and with fewer separate placebo groups. NIO752 Phase 3 study (novartis.com) PSP Trial Platform award (taggs.hhs.gov) However, important caution is warranted: two large Phase 2 anti-tau antibody studies, gosuranemab and tilavonemab, did not demonstrate a clinical benefit on PSP progression despite sound biological rationale and evidence that the drugs reached their intended targets. Gosuranemab Phase 2 trial (pubmed.ncbi.nlm.nih.gov) Tilavonemab Phase 2 trial (pubmed.ncbi.nlm.nih.gov)

PSP is especially difficult to treat because diagnosis often occurs after substantial neuron loss; several clinical phenotypes progress at different rates; tau pathology is largely inside cells; and a treatment that reduces a biomarker may not restore lost neural circuits or improve daily function. Clinical prognostic factors in PSP (pubmed.ncbi.nlm.nih.gov) Biomarkers of PSP progression (pmc.ncbi.nlm.nih.gov) RNA drugs may require repeated lumbar punctures, antibodies require repeated infusions, and even successful treatments could face cost, travel, trial-access, and caregiver-burden barriers. NIO752 Phase 3 study (novartis.com) Bepranemab Phase 1b trial (pubmed.ncbi.nlm.nih.gov)

Outlook and Future Directions

As of August 8, 2026, PSP has no cure and no validated disease-modifying therapy, so it would be premature to describe any current program as curative. NINDS PSP overview (ninds.nih.gov) The milestones to watch are whether NIO752 can show that lowering tau production changes clinical decline in its Phase 3 trial, whether the PTP can efficiently identify a reproducible Phase 2 signal for AADvac1, LM11A-31, or future regimens, and whether biomarkers can enable treatment earlier in the disease course. NIO752 Phase 3 study (novartis.com) PSP Trial Platform enrollment (psp.org) A realistic near-term goal is a therapy that safely slows decline; a true cure will likely require very early intervention, durable control of tau-related injury, and eventual restoration or preservation of damaged neural networks. PSP midbrain organoid model (pubmed.ncbi.nlm.nih.gov)

References

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