Peter Schueler

Senior Vice President, Drug Development Services

Parkinson’s disease is the second most common neurodegenerative disorder after Alzheimer’s disease.

The anti-Parkinson disease medications currently available primarily promote dopamine levels in the brain to compensate for the loss of dopamine due to neuro-degeneration. Apart from the need to better manage symptoms in advanced stages of the disease, there is an even greater need to develop neuro-protective or neuro-regenerative therapies to slow, stop or reverse disease progression.

Taking into consideration the lessons learned from Alzheimer’s disease studies could therefore benefit the design of such neuro-protective studies. These are summarised as follows: 

  1. Target early disease stages: In most neurodegenerative diseases, symptoms only occur when more than 70% of the relevant nerve cells are already compromised. Neuro-regenerative therapies that may still work at such a late stage are not yet on the horizon.
  2. Make sure the study population is sufficiently homogeneous: With more precise diagnostic tools, it becomes evident that a clinical diagnosis of Parkinson’s disease may be wrong in about 15% of cases. 
  3. Don’t rush into costly, large, phase III studies: Take the time to explore preliminary evidence of efficacy, suitable therapeutic dosage ranges and proper patient population in phase II clinical development. 
  4. Explain to study subjects and caregivers that they should not expect improvements of Parkinson’s disease symptoms, although they may benefit from a slower disease progression over time. 
  5. Take special measures to ensure adherence to the investigational product for non-injectable therapies: Patients who received education were 96% adherent at six months, whereas with no education, adherence was 58.5% at six months. 
  6. Do not rely on biomarkers, but put clinical outcomes as an endpoint in phase II trials: If the validity of a biomarker is not fully proven, it should not be used to take milestone-related decisions in the development plan. 

Taking all these lessons learned into consideration could markedly lower the risk of a false negative result in clinical trials for disease-modifying therapies against Parkinson’s disease.

For more information on this topic, please contact us.

This blog is an edited version of “Key Considerations for Disease-Modifying Parkinson’s Disease Trials” which appeared in Pharmaceutical Market Europe in November 2018. To view the full article, please visit

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