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The Parkinson's Disease Biomarker: A Critical Missing Link for Understanding PD, Currently Under Investigation by The Michael J. Fox Foundation

One of the greatest hurdles to developing new treatments for Parkinson's disease — particularly therapies that prevent, slow or reverse the progression of the disease — is the lack of clear and reliable PD biomarkers. From 2002 to 2010, The Michael J. Fox Foundation (MJFF) invested over $28 million in biomarker discovery and development, setting the stage for a comprehensive study to validate promising biomarkers of Parkinson's disease. In 2010, MJFF — in collaboration with industry partners and generous funders — launched the Parkinson's Progression Markers Initiative (PPMI), a $45-million landmark study to definitively verify biomarkers of Parkinson's disease.

So what is a biomarker? In general, a biomarker is defined as a substance, process or characteristic in the human body that can be correlated with the risk or presence of a disease, or that changes over time in a way that can be linked to disease progression. For example, blood pressure can be objectively and easily measured and serves as a biomarker of both normal cardiovascular function, and (when high) of potential cardiovascular disease.

Parkinson's disease is a complex neurodegenerative disorder with many underlying causes that may differ among individuals. For this reason, identifying a biomarker — or set of biomarkers — for PD requires sophisticated methods of measurement targeted at various aspects of the disease. PPMI uses advanced imaging, biologic sampling and clinical and behavioral assessments to evaluate a cohort of 400 recently diagnosed Parkinson's patients who are not yet on medication and 200 control participants who do not have a close relative with PD.

Identifying biomarkers will be transformative to the PD community, allowing scientists to objectively diagnose, monitor and predict the disease. Currently, there is no way to definitively diagnose Parkinson's disease in a living person. Instead, a diagnosis is based on the presence of clinical symptoms including resting tremor, rigidity, and bradykinesia (slow movement).

In addition to aiding diagnosis, PD biomarkers are critical to developing long-awaited disease-modifying treatments for PD, enabling researchers to concretely determine whether a candidate therapy is, or is not, impacting disease course in PD patients. Furthermore, a biomarker that can identify people with PD — or those at risk — could make it possible to intervene with protective and preventative therapies (once available) before significant dopamine neuron loss has occurred.

PPMI is the first clinical study to assemble a population of sufficient size and collect biologic samples and clinical information, draw meaningful scientific conclusions over time, and try to develop better ways to measure the progression of PD. All biosamples and clinical data acquired from the study's participants will be made available to qualified researchers around the world in a comprehensive Parkinson's database. By fostering such collaboration within the scientific community, PPMI will help increase the pace of biomarker validation and clinical testing as well as accelerate the pace of discovery.

PPMI is currently under way in 19 sites across the United States and Europe. Two additional European sites are set to launch in fall 2011, and the Foundation is exploring the possibility of bringing PPMI to Australia by 2012, making it a truly global study. PPMI is an opportunity to be part of a new model focused on collaboration and knowledge sharing — with a goal of creating the tools that will enable the development of transformational therapies, and ultimately a cure, for Parkinson's. To learn more about PPMI or to find a site near you, visit michaeljfox.org/ppmi or call 877-525-7764.

July 2011