Two projects aimed at improving understanding of the placebo effect in clinical trials for Parkinson’s disease have been allocated funding by the US-based Michael J Fox Foundation (MJFF) for Parkinson’s Research.

The placebo effect has increasingly complicated the interpretation of outcomes in Parkinson’s disease (PD) trials, raising “a significant hurdle to the development of new treatments”, notes the Foundation, which held a placebo response workshop in March 2009. As the effect involves the dopamine system, which degenerates in PD, it may have more of an impact in clinical trials for Parkinson’s than for other diseases, the MJFF suggests.

As part of a clinical trial in dyskinesia announced by the Foundation last December, a pilot study will seek initially to validate surveys that can predict how the placebo response is affected from person to person by disease- and treatment-related variables, as well as by the individual characteristics of patients and investigators involved in clinical research.

The pilot will assess the potential usefulness of the placebo surveys in future clinical trials and provide ancillary information on the susceptibility of various dyskinesia rating scales to placebo effects.

Surveys run with patients and investigators at the outset of the study will gather data on personal traits including optimism, social conformity and expectations of outcome. When the study is completed, the survey results will be tracked with study outcomes to determine the impact of optimism and expectation of a positive outcome on the effectiveness of the rating scales.

The pilot study will be conducted by researchers Dr Mark Stacy at Duke University and Dr Glenn Stebbins at Rush University Medical Center.

In the second project, a Columbia University team led by Drs Tor Wager and Daphna Shohamy will use functional magnetic resonance imaging (MRI) to examine brain activity in Parkinson’s patients as they execute specific motor and learning tasks, comparing how the activity changes when patients are given levodopa, the gold-standard drug treatment for Parkinson’s, or placebo.

Previous imaging studies have demonstrated that placebo treatments can increase dopamine levels in patients’ brains, the Fox Foundation points out. However, it adds, there is little experimental evidence to suggest the effect is tied to functional improvement on the Unified Parkinson’s Disease Rating Scale (UPDRS), the tool used by clinicians to measure effects of experimental treatments.

Drs. Wager and Sohamy will assess the potential of functional MRI to provide that evidence, with the wider goal of establishing more fully biological markers of placebo effects in Parkinson’s and determining whether these effects lead to measurable functional improvement in PD patients.