Rethinking Inclusion Criteria to Increase Generalizability, Patient Participation in Parkinson Disease Trials: Camille Carroll, MD

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"If we don’t recruit [patients] into trials in an inclusive and diverse way then we might miss safety signals. We might miss different aspects of disease presentation in different subgroups and then that has implications for the way that we treat patients."

Movement disorder experts recently reviewed the current landscape of disease-modifying therapies in Parkinson disease (PD) during a session at 2025 International Congress of Parkinson’s Disease and Movement Disorders (MDS), held October 5-9, in Honolulu, Hawaii. There, presenters highlighted lessons from past efforts, insights from ongoing studies, and strategies for shaping future clinical research. Chaired by experts Susan Fox, MD, PhD, and Nobutaka Hattori, MD, PhD, the discussion brought together leading trial investigators to examine evolving study methodologies and persistent challenges in the field.¹

In the session, Tanya Simuni, MD, provided an overview of recent and ongoing PD trials aimed at disease modification, emphasizing advances in targeting α-synuclein, mitochondrial dysfunction, and neuroinflammation. Further along into the session, Camille Carroll, MD, PhD, discussed the complexities of patient selection, while Jean-Christophe Corvol, MD, PhD, addressed key considerations for clinical trial design. Collectively, experts in this presentation underscored the need for greater precision, inclusivity, and innovation in PD trial design to accelerate the identification of truly disease-modifying therapies.

In an interview with NeurologyLive^®, Carroll, professor of clinical neuroscience at Newcastle University, outlined the challenges of patient selection in PD clinical studies. She emphasized how eligibility criteria should align with the specific research questions for each trial phase. Camille highlighted that phase 1 focuses on safety and tolerability, phase 2 determines efficacy in more homogeneous populations, and phase 3 assesses real-world benefit across diverse patient groups. She also noted the evolving approach to inclusion criteria, such as incorporating patients already on levodopa in later-phase trials, to minimize confounding factors and better reflect clinical practice.

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REFERENCES
1. Carroll C. Challenges in Patient Selection. Presented at: 2025 MDS Congress; October 5-9; Honolulu, Hawaii. Disease-Modifying Trials for Parkinson’s Disease: Past, Present, and Future.