Objective: To identify the most common causes of participant’s screen failure (SF) and drop-out (DO) in Phase 2 and 3 Disease Modification Therapy (DMT) trials in Parkinson’s Disease over the last 10 years.

Background: Numerous PD trials face delays due to high screening SF and DO.  Identifying common causes of SF and DO would significantly optimize future trial designs.

Method: Phase 2 and 3 industry-sponsored, interventional PD DMT trials (>30 patients) completed within the last decade were identified via CT.gov and Parexel databases. Data were extracted from published literature, supplementary materials, protocols, abstracts, CT.gov, and internal Parexel database records. Studies on non-motor symptoms, atypical parkinsonism, basket trials, mutation-specific populations, or biomarkers were excluded. Trials lacking sufficient data were omitted from analysis.

Results: Of 54 eligible PD DMT trials, 22 provided analyzable data. Most trials were in early-stage PD (77%), with 13% mid-stage and 9% mid-to-advanced. 54.5% recruited levodopa-treated patients, 22.7% drug-naïve, and others trialed mixed populations of drug-naïve and treated (with levodopa, MAO-B inhibitors, amantadine or anticholinergics). Average trial duration was 85 weeks (range 24-240). Mean screen failure rate (SFR) was 30% (range 1-65%); most between 10-30% (18.8%) or 30-50% (13.64%). Mean dropout rate (DOR) was 15% (range 0-74%); majority falling under 20% (34%). Most common SF causes (data from 19 trials) were “other”, patient decline, comorbidities, and PD stage/duration. Most common DO reasons (data from 20 trials) were adverse events, inability to adhere to study procedures, consent withdrawal, and loss to follow-up. Trials restricting initiation of PD therapy or restriction in dose changes showed higher DORs (25% and 18%). DORs were similar among disease stages and requirements for motor diary completion.

Conclusion: Participants of PD DMT trials demonstrate high commitment, with low attrition rates. Screen failure rates vary but seldom exceed 50%, primarily influenced by patient decision. Enhancing patient education on trials and investigational agents through consistent investigator-patient communication will help boost patient confidence on trial participation. Strategies to enhance subject retention should prioritize reducing patient burden and PD medication restrictions during the trial.

« Back to 2025 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/trends-on-recruitment-and-retention-in-parkinsons-disease-modification-trials/