An Open-label Safety Study of Dipraglurant in Patients with Parkinson's Disease Receiving Levodopa-based Therapy With or Without Concomitant Dopaminergic Medications

This open-label protocol evaluated the long-term safety and tolerability of dipraglurant (ADX48621) in people with Parkinson's disease (PD) who are receiving levodopa-based therapy. Implemented as a Phase 2/3 extension study, the trial enrolled patients who had completed an Addex-sponsored randomized, double-blind trial of dipraglurant and who, in the judgment of site investigators, might benefit from continued open-label treatment. The primary objective was to observe safety and tolerability outcomes during up to 52 weeks of dipraglurant exposure, administered three times daily at total daily doses in the 150–300 mg range. The study design required participants to take the study drug thrice daily, spaced by no less than three hours, and to maintain a stable antiparkinsonian medication regimen, including levodopa given at least three times daily; stability of concomitant medications was to be maintained for the initial four weeks of treatment.

Seventeen participants were enrolled across multiple U.S. academic and clinical sites, reflecting a geographically diverse network including Augusta University, University of Kansas Medical Center, Rutgers (State University of New Jersey), Icahn School of Medicine at Mount Sinai, The Ohio State University Wexner Medical Center, Abington Neurologic Associates, and the University of Pennsylvania. The study began October 25, 2021, with an estimated completion date of August 15, 2022; however, the overall study status is listed as Terminated as of the last posted update. Participants included men and women aged 30 to 85 years who had clinically completed the parent randomized study and were considered appropriate by investigators for continued open-label therapy. The protocol excluded patients judged inappropriate by investigators, those using amantadine (including extended-release formulations) or memantine throughout the study, and those using marijuana or cannabinoid products during the initial four weeks of participation, among other protocol-defined exclusion criteria.

The intervention arm consisted of dipraglurant administered thrice daily (TID). As an investigational small-molecule therapy targeting dyskinesias associated with long-term levodopa use, dipraglurant’s evaluation in this extension study focused on tolerability across a broader exposure window, monitoring adverse events, clinical laboratory results, and potential interactions with standard dopaminergic regimens. While the publicly available listing emphasizes safety and tolerability rather than efficacy endpoints, the open-label format allowed investigators to observe longer-term safety signals and tolerability in a real-world-like context following controlled trial participation. Enrollment was modest, reflecting the targeted population of prior dipraglurant trial completers, and site listings indicate coordination among several established neurology centers across North America.

This trial listing provides a concise overview of eligibility criteria, study procedures, dosing parameters, enrolled population, and participating sites, positioning the study as a company-sponsored safety extension intended to inform the risk profile of dipraglurant during prolonged exposure in patients receiving levodopa-based therapy for Parkinson’s disease with dyskinesias.