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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, relentlessly progressive brain disorder and a form of atypical parkinsonism. It damages circuits involved in balance, movement, thinking, swallowing, speech, and voluntary eye movements; early unexplained backward falls and difficulty looking up or down are especially characteristic. PSP usually begins in the mid-to-late 60s, although onset and presentation vary. It is a primary “4-repeat tauopathy,” meaning that abnormal forms of the tau protein accumulate in nerve cells and supporting brain cells. NINDS PSP overview 4R-tau pathology study

PSP commonly causes severe disability within three to five years after symptoms begin, and Richardson syndrome—the most common clinical form—often has a survival of roughly five to seven years from symptom onset. There is no approved treatment that stops or reverses the disease. Current care is therefore multidisciplinary and symptom-focused: fall prevention and physical therapy, speech and swallowing assessment, communication support, nutrition planning, management of mood or sleep symptoms, and carefully selected medication trials for stiffness or slowness, although levodopa usually has limited benefit. NINDS PSP overview Structural correlates of survival in PSP

Scope of Recent Research (2020–present)

Since 2020, PSP research has become more clinically actionable, with work concentrated on lowering tau production, blocking tau propagation, reducing inflammation and neurodegeneration, improving early diagnosis, and building trial infrastructure suitable for a rare, rapidly progressing disease. The field has not yet produced a curative therapy, but it has moved beyond purely symptomatic studies: the most consequential development is a recruiting Phase III trial of the tau-lowering antisense oligonucleotide NIO752, alongside biomarker-driven and platform-trial efforts designed to test several disease-modifying candidates more efficiently. NIO752 Phase III trial PSP Clinical Trial Platform award

Major Breakthroughs and Emerging Therapies

The leading strategy is tau lowering with antisense oligonucleotides (ASOs). ASOs are short synthetic strands of nucleic acid designed to bind a target RNA message; in this case, they aim to reduce production of tau from the MAPT gene before it can misfold and aggregate. NIO752 is administered into cerebrospinal fluid by intrathecal injection. This approach is supported by preclinical work showing that a MAPT-targeting ASO lowered tau messenger RNA and protein in human neurons, mice, and nonhuman primates, with brain tau reduction in primates persisting for about 20 weeks after dosing. MAPT-targeting ASO preclinical study NIO752 Phase III trial

A second emerging direction targets LINE-1 retrotransposon activity and innate immune activation rather than tau directly. LINE-1 is a normally restrained, virus-like genetic element; its abnormal activity may trigger inflammatory responses in PSP. In 2026, a placebo-controlled Phase IIa study reported that the oral reverse-transcriptase inhibitor TPN-101 was well tolerated and showed dose-related reductions in cerebrospinal-fluid neurofilament light chain (NfL), a marker of axonal injury. However, it did not improve the PSP Rating Scale during the 24-week blinded treatment period, so its clinical benefit remains unproven. TPN-101 Phase IIa trial

Anti-tau antibody programs have provided an important negative but informative result. In the 486-participant PASSPORT Phase II trial, gosuranemab reduced unbound N-terminal tau in cerebrospinal fluid by 98%, demonstrating biological target engagement, but it did not slow clinical progression on the PSP Rating Scale or secondary clinical outcomes after 52 weeks. This result suggests that removing or neutralizing one extracellular tau species is not, by itself, sufficient to alter PSP’s clinical course; it has strengthened interest in earlier intervention, different tau targets, intracellular tau reduction, and combination approaches. Gosuranemab PASSPORT trial

Gene- and cell-based approaches remain exploratory rather than clinical treatments for PSP. Examples include viral gene-delivery concepts intended to simultaneously suppress toxic tau production and provide an aggregation-resistant tau form, small molecules that enhance autophagy—the cell’s protein-clearance system—and patient-derived neuron models used to test compounds in human cellular backgrounds. These programs could eventually support a restorative or preventive strategy, but they remain far from demonstrating that lost neurons or complex brain networks can be rebuilt in people with PSP. CurePSP 2021 venture grants

Clinical Trials and Experimental Approaches

The most advanced tau-directed program is Novartis’s PRESERVE study of NIO752, a recruiting randomized, double-blind, placebo-controlled Phase III trial in people with probable or possible PSP Richardson syndrome. The study began on June 3, 2026, plans to enroll 300 participants, and includes an open-label extension after the blinded period; its listed completion date is July 18, 2031. The preceding Novartis-sponsored Phase I multiple-ascending-dose study, NCT04539041, was completed in October 2024, but no study results were posted in the ClinicalTrials.gov record reviewed for this report. NIO752 Phase III trial NIO752 Phase I registry record

Transposon Therapeutics’ TPN-101 completed a Phase IIa trial in 42 participants with probable PSP. Participants received one of three oral doses or placebo for 24 weeks, followed by a 24-week open-label period. The peer-reviewed report found reassuring short-term tolerability and biomarker signals—particularly lower cerebrospinal-fluid NfL at higher doses—but no between-group difference on the PSP Rating Scale during the blinded phase. Thus, TPN-101 remains an experimental neuroprotection candidate rather than evidence of a cure or established disease-modifying treatment. TPN-101 Phase IIa trial

A major enabling experiment is the NIH-supported Progressive Supranuclear Palsy Clinical Trial Platform, led through the University of California, San Francisco. The project is designed to recruit 440 participants at approximately 50 North American sites and to test therapies using shared controls, clinical outcomes, MRI, cerebrospinal-fluid markers, and biospecimen collection. A platform design can add new treatment arms over time, potentially reducing the cost, delay, and participant numbers needed for separate conventional trials. PSP Clinical Trial Platform award

Methodologies and Scientific Approaches

Researchers combine laboratory models with increasingly sophisticated human measurements. Preclinical programs use genetically engineered tau mice, cultured human neurons, patient-derived induced pluripotent stem-cell neurons, and nonhuman primates to test whether a therapy reaches relevant brain cells, lowers tau, improves protein clearance, or reduces inflammatory injury. Human tissue studies also matter because PSP tau is present not only in neurons but in astrocytes and oligodendrocytes, making it essential to understand which cell types a therapy must reach. MAPT-targeting ASO preclinical study Cell-specific MAPT expression in PSP

Clinical studies increasingly use biomarker panels alongside symptom scales. Tau positron-emission tomography (PET), structural MRI measures such as the midbrain-to-pons ratio, and cerebrospinal-fluid or blood NfL can help distinguish PSP from Parkinson’s disease and related disorders. One BioFINDER-2 study found that combining tau PET, MRI, and cerebrospinal-fluid NfL gave stronger group-level diagnostic separation than individual measures alone. Connectivity mapping, tau PET, and postmortem pathology are also being used to investigate how tau deposits may spread across connected brain networks. PSP biomarker comparison study Tau connectivity and deposition study

Leading Institutions and Funding

Novartis is currently the principal industry sponsor of a late-stage PSP disease-modification study through the Phase III NIO752 program. UCSF and a network including CurePSP Centers of Care, the Parkinson’s Study Group, the ALLFTD research network, and the NIH Alzheimer’s Disease Clinical Trials Consortium are building the PSP Clinical Trial Platform. The NIH award supporting that platform totals approximately $30.3 million across fiscal years 2024 and 2025. NIO752 Phase III trial PSP Clinical Trial Platform award

Patient-focused philanthropy remains especially important because PSP is rare. CurePSP and the Rainwater Charitable Foundation jointly awarded nearly $400,000 in Pathway and Pipeline grants in 2025 for PSP and corticobasal degeneration research, including work on genetic and cellular models, biomarkers, microglia, disease mechanisms, and therapeutic development. Rainwater reported $28.5 million in medical-research giving during 2023–2024 across primary tauopathies, while CurePSP’s 2026 New Investigator Awards offer up to $100,000 for one- or two-year pilot studies. CurePSP–Rainwater 2025 grants Rainwater Medical Research Program CurePSP research grants

Strengths, Limitations, and Challenges

The field’s strongest feature is its growing ability to test whether an intervention reaches its intended biological target. ASOs can directly lower tau production, TPN-101 has shown measurable effects on injury and inflammatory biomarkers, and multimodal imaging and fluid markers can improve participant selection and monitoring. The Phase III NIO752 study and the NIH platform trial are signs that PSP research is progressing from isolated small studies toward larger, more rigorous efficacy testing. NIO752 Phase III trial TPN-101 Phase IIa trial PSP Clinical Trial Platform award

The central limitation is that changing a biomarker has not reliably changed how patients feel or function. Gosuranemab dramatically lowered free tau in cerebrospinal fluid yet did not slow clinical decline, while TPN-101 improved biomarker trajectories without demonstrating a blinded clinical-scale benefit. PSP also progresses quickly, is biologically diverse, is often diagnosed after substantial neuronal loss, and includes tau pathology across several cell types and brain regions. Intrathecal therapies may impose logistical burdens, and even a successful disease-slowing therapy would not automatically repair already lost neurons, reverse disability, or ensure broad access. Gosuranemab PASSPORT trial TPN-101 Phase IIa trial Cell-specific MAPT expression in PSP

Outlook and Future Directions

As of October 4, 2026, a cure for PSP is not near, but the field has reached a more credible disease-modification era: a tau-lowering ASO is in Phase III, inflammatory and neurodegeneration pathways have produced testable biomarker signals, and a major platform trial infrastructure is being assembled. The milestones to watch are whether NIO752 shows a clinically meaningful slowing of progression, whether biomarker changes can be validated as predictors of real-world benefit, whether platform trials can efficiently identify additional active treatments, and whether therapies can be deployed early enough—potentially in combinations—to preserve neurons before irreversible loss occurs. NIO752 Phase III trial PSP Clinical Trial Platform award

References

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