At the screening visit consenting patients will be screened for eligibility according to study specific inclusion/exclusion criteria within 8 weeks before start of Investigational Medicinal Product (IMP) administration. A diary concordance training will be performed and following the screening visit the patient will be asked to self-administer three 24-hour home diaries and to bring the completed diaries to the baseline visit for assessment prior randomization.~At the baseline visit, patients will be randomized to receive one of three doses of mesdopetam (dose 1, dose 2 and dose 3) or placebo b.i.d.~During the first week a dose run-in phase will take place, where all patients allocated to mesdopetam will receive a run-in dose of mesdopetam twice daily and patients allocated to placebo will receive placebo twice daily. At Visit 2, patients will receive mesdopetam dose 1, dose 2 or dose 3 or placebo b.i.d., as randomized and continue the same dose for the rest of the treatment period until EOT. Dose reductions are restricted and the dose can only be reduced once. Dose reductions are permitted from visit 2 (day 9) until visit 3 (day 28), where after the dose should be kept stable until EOT.~The treatment allocation will be double-blind, i.e. it will not be disclosed to the patients, the site staff or the Sponsor.~During the treatment period, changes in disease state and ON phase dyskinesia will be assessed using the MDS-UPDRS, the modified UDysRS (i.e. parts 1, 3 and 4), and Clinician's Global Impression of Severity (CGI-S). Furthermore, patients will self-administer three 24-hour home diaries prior to visit 3 (week 4), visit 4 (week 8) and visit 5 (week 12) to assess daily motor function.~Blood samples for pharmacokinetic (PK) analysis will be collected at visit 4 (week 8) and visit 5 (week 12).~Visit 6 (follow-up) will be performed for all patients, including any patients that discontinue the IMP early, 5-8 days after last administration of IMP.
This is a Phase 2b study investigating the efficacy and safety of mesdopetam as adjunct therapy on daily ON-time without troublesome dyskinesia in patients with Parkinson disease. Mesdopetam is taken for 84 days.