Surrogate endpoints in Parkinson's disease research.

Biomarkers are important tools in understanding the underlying mechanisms of causation, progression, and treatment effects in Parkinson's disease (PD). In addition, these biomarkers may be utilized as surrogate endpoints that, when used appropriately, can lead to important advances in therapeutics in a timely and cost-effective manner. This paper outlines the definition, role, validity process, and risks associated with surrogate endpoints. The use of biomarkers in recent PD clinical trials is discussed and potential shortcomings and unanswered questions related to interpreting these outcomes are reviewed. Finally, the significant challenges that lie ahead for validating and interpreting surrogate endpoints in PD are addressed.