Abstract
INTRODUCTION: There is a need for new therapies in Parkinson's disease that may help to address known limitations of current options. PF-06649751 is a novel, highly selective dopamine D1/D5 agonist targeted for Parkinson's disease treatment. METHODS: The safety, pharmacokinetics, and pharmacodynamics of PF-06649751 were assessed in single ascending dose and multiple ascending dose clinical trials in patients with Parkinson's disease. The single ascending dose study (N = 18) was a double-blind, placebo-controlled study with a three-way crossover design consisting of three treatment periods separated by 7-day study drug washout periods. PF-06649751 doses were 0.75 mg, 1.5 mg, 3 mg, 6 mg, and 9 mg. In the open-label multiple ascending dose study, eligible subjects received once-daily doses of PF-06649751 (N = 45) over 21 days, with up-titration to 5 mg, 15 mg, and 25 mg once daily. Pharmacodynamics were assessed by measuring change from baseline in the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III at different time points post dose. RESULTS: PF-06649751 was safe and well tolerated across studies and in all cohorts. Peak plasma concentrations were attained 1-4 h post dose across both studies, and exposure increased with increasing dose. PF-06649751 demonstrated sustained pharmacodynamic effects compared with placebo, with mean reductions from baseline in the MDS-UPDRS Part III up to 12 h post dose at 9 mg single dose. MDS-UPDRS Part III changes in the open-label multiple dose study on day 22 also demonstrated sustained pharmacodynamic activity. CONCLUSIONS: PF-06649751 represents a novel therapeutic candidate for Parkinson's disease with an initial safety, tolerability, and pharmacokinetic profile and potential for efficacy that merits further study in larger clinical trials. TRIAL REGISTRATION: These studies are registered at www.clinicaltrials.gov as NCT02373072, NCT02224664. FUNDING: Pfizer.