Racial and ethnic diversity in clinical trials for disease-modifying drugs in PD: Systematic review 

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In the past few years, the development of clinical trials focusing on disease-modifying therapies has transformed Parkinson’s disease (PD) research, with an emphasis on slowing disease progression rather than just treating symptoms. However, a critical question remains: Who is truly being represented in these trials?  

Our group reviewed and analyzed data on racial and ethnic diversity in randomized clinical trials (RCTs) for potential Parkinson’s disease (PD) treatments. We looked at 37 large, international double-blind and placebo-controlled trials with over 11,000 participants. Nearly half of these trials did not report on race or ethnicity, making it difficult to evaluate differences in participant backgrounds. Only 19 out of the 37 studies (51.4%) shared information about participants’ race or ethnicity. In these studies, the majority of participants were white, with only 251 out of 5,735 (4.38%) being non-white. The breakdown of non-white participants was as follows: Asian made up 61.4% of the 251 non-white participants, black accounted for 20.3%, Hispanic for 7.6%, Hawaiian for 0.4%, American Indian/Alaska native for 1.6%, and other/multiracial for the remaining 51. Overall, white participants made up 98% of all trial enrollments, totaling 10,888 people.  

These findings are concerning and significant because Parkinson’s disease affects individuals from all racial and ethnic backgrounds. Therefore, clinical trials should reflect these diverse populations to ensure that new treatments are effective across different groups. Genetic ancestry, environmental exposures, healthcare access, and social determinants of health all influence disease risk, progression, and treatment response. Studying diverse participants helps researchers understand variability and ensures that study findings are applicable to patients in clinical practice.  

Researchers, sponsors, funding agencies, healthcare professionals, patient advocacy organizations, and communities must work together to enhance diversity in clinical studies for Parkinson disease. Strategies such as community partnerships, multilingual recruitment, financial support, and accessible research sites might be potential options to reduce participation barriers. As newer and more effective treatments transition to clinical practice, ensuring full representation in trials is crucial. Better representation makes research equitable, strengthens evidence, and makes treatments more relevant for the global Parkinson’s community. 

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