Data from Dr Cornelia Meisenberg - Curated by EPG Health - Last updated 21 June 2019

What is Progressive Supranuclear Palsy (PSP)?

According to the National Institute of Neurological Disorders and Stroke, progressive supranuclear palsy (PSP) is a degenerative disorder that affects between 3–6 people in every 100,000.1 Since PSP is an uncommon disease that shares many early signs and symptoms with Parkinson’s disease, many healthcare professionals often misdiagnose PSP patients as having Parkinson’s disease. Indeed, PSP falls into a group of diseases known as Parkinson’s plus syndrome or atypical Parkinsonism.2

As the name suggests, PSP sufferers experience a progressive loss of control that arises from deterioration of brain regions located above nerve cell clusters (supranuclear regions). At the early stages, PSP sufferers show reduced control of movement and balance which may lead to falling and changes in gait, such as leaning backward. Other early symptoms include behavioural changes and blurring of vision. At the later stages, PSP patients have trouble in controlling eye movements, speech and swallowing, and ultimately develop dementia.

Whilst comparisons to Parkinson’s disease are valid at the early stages, PSP progresses more quickly and causes more severe symptoms. PSP sufferers also do not respond very well to Parkinson's medication, and have a significantly reduced life expectancy.2 With good attention to medical and nutritional needs, it is possible for individuals with PSP to live a decade or more after the appearance of the first symptoms. However, the prognosis for PSP typically sees patients becoming severely disabled within three to five years of onset.1

What causes PSP?

The exact cause of PSP remains unknown. There is little evidence to suggest a single genetic contributor since PSP onset appears to be sporadic, and sufferers typically do not present a family history of the disease.1

The most recognisable feature of PSP is the abnormal accumulation of protein tau deposits at nerve cells, known as neurofibrillary tangles (NFT). In its normal state, tau is associated with microtubules which support nerve axon structures and intracellular transport of nutrients and other important cellular factors. However, abnormal tau deposits are thought to lead to nerve cell death and is also apparent in other neurodegenerative diseases such as Alzheimer’s disease, corticobasal degeneration, and some forms of frontotemporal degeneration which are classed as tauopathies. A key research focus is therefore to identify ways to prevent the harmful clumping of tau, as a potential treatment for these disorders.

Is there a cure / treatment for PSP?

As a complex illness, there are currently no effective, specific treatments or cures for PSP. Drugs used to treat Parkinson’s have shown limited effectiveness, although 20-30% of PSP patients respond quite well to levodopa, at least initially.2

Some symptoms can be managed with other interventions and a combination of approaches will probably be suggested involving consultations between neurologists and physiotherapists, speech and language therapists, occupational therapists, specialist nurses, dieticians and social workers.

Is there anything on the horizon?

The humanized IgG4 monoclonal anti-tau antibody has shown signs of hope since its development in 2014.3 This antibody reportedly neutralises the toxicity of eTau in mouse models of frontotemporal dementia and has been further developed by Biogen as BIIB092. It is currently an experimental therapy for the treatment of diseases with toxic aggregates of tau protein, including Alzheimer’s disease and PSP.4

PASSPORT clinical trial

The phase 2 PASSPORT clinical trial (NCT03068468) is looking at BIIB092 efficacy against placebo in treating patients with PSP. The trial also focuses on the safety and tolerability of BIIB092 over a 52-week period and is due to complete in March 2020.5

What next?

Whilst research into a treatment for PSP continues, it is hoped that similar research on related and more common diseases with shared features, such as Parkinson’s and Alzheimer’s diseases, will provide more clues to unlock insights into PSP. In turn, it may be that research into PSP provides answers for similar degenerative diseases.

Related content:
How close are we to a disease-modifying treatment for Alzheimer’s?
EPAD – Changing the way we think about Alzheimer’s prevention


References

1. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Progressive-Supranuclear-Palsy-Fact-Sheet
2. https://www.epda.eu.com/about-parkinsons/types/progressive-supranuclear-palsy-psp/
3. Bright J et al. Human secreted tau increases amyloid-beta production. Neurobiol Aging. 2015;36(2):693–709.
4. https://www.alzforum.org/therapeutics/biib092
5. http://www.io.nihr.ac.uk/wp-content/uploads/2019/02/15108-BIIB092-for-PSP-V1.0-FEB2019-NON-CONF.pdf

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