The time between diagnosis and implementation of symptomatic treatment is critical in the effort to find a cure for Parkinson’s disease. However, many early Parkinson’s patients wait too long before seeking medical attention, leaving researchers with a small group of candidates for clinical trials, says Robert A. Hauser, MD, the director of the Parkinson’s & Movement Disorder Center at the University of South Florida.
In his commentary, “Help cure Parkinson’s disease: please don’t waste the Golden Year,” published in the journal npj Parkinson’s disease, Hauser stresses the importance of early Parkinson’s patients participating in clinical trials before they start taking symptomatic medications.
The discovery that Parkinson’s is associated with aggregation of misfolded alpha-synuclein proteins in the central nervous system suggests there are many potential targets for therapeutic intervention.
Researchers are enthusiastic about the idea that the disruption of this process, or removing toxic aggregates, can slow or stop disease progression. Unfortunately, there are still no validated biomarkers, such as a simple blood test, that can help monitor disease progression or test promising therapies in Parkinson’s patients.
So far, the most common way to test a therapeutic candidate is to assess its capacity to slow the progression of clinical signs and symptoms compared with placebo over time in patients with early Parkinson’s who are not yet receiving symptomatic Parkinson’s medications — such as levodopa, dopamine agonists, and MAO-B inhibitors.
However, this can prove to be a challenge, since patients with early Parkinson’s disease can only be followed, without the use of symptomatic medication, for about six to 12 months, what Hauser calls the “Golden Year.” After this, many patients will need medication to relieve symptoms.
“The critical time of about one year from when the patient can be diagnosed with early PD [Parkinson’s disease] based on mild classic motor features until they truly require symptomatic therapy can be considered the Golden Year,” Hauser said in a press release. “It is during this early, untreated phase, that progression of clinical symptoms reflects the progression of the underlying disease.”
Interference from symptomatic medications makes it difficult for researchers to tell if the potential treatment being tested is slowing disease progression or if they are just seeing effects from those other therapies.
However, patients with early Parkinson’s who are available to enroll in a clinical trial and whose symptoms are mild enough are in short supply.
Therefore, to test promising potential disease-modifying therapies, patients with early Parkinson’s have to be identified and referred to clinical trials before they go on symptomatic medications. Unfortunately, this is often not the case.
“If the time period over which we test the intervention is short, we reduce our ability to identify a difference between the intervention and placebo. If the time period over which we attempt to test the medication is too long, a substantial proportion of patients may require institution of symptomatic therapy and we lose our ability to monitor clinical disease progression during the observation period,” Hauser wrote.