Evaluation of D1/D5 Partial Agonist PF-06412562 in Parkinson's Disease following Oral Administration.

Background: PF-06412562 is a moderately potent, highly selective oral D1/D5 dopamine receptor partial agonist.

Objective: To study the efficacy and safety of a single, oral, split dose of PF-06412562 in patients with Parkinson's disease.

Methods: Following overnight levodopa (L-dopa, Sinemet®) washout, subjects received a single dose of levodopa in open-label period 1. Periods 2 and 3 had a double-blinded, sponsor-open, randomized, 2-way cross-over, placebo-controlled design, during which subjects were randomized to PF-06412562 30 mg (+ 20 mg 4 h later) or placebo. Maximum percent improvement from baseline in finger-tapping speed (measure of bradykinesia) measured using KinesiaTM technology (as the primary end point) and change from baseline in the Movement Disorder Society's Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS-III) motor section scores (the preferred exploratory end point) were evaluated.

Results: Nineteen subjects received levodopa; 13 met the period 2/3 entry criteria and received PF-06412562, 30 + 20 mg, or placebo. The prespecified primary efficacy criterion for significant improvement in finger-tapping was not met due to inconsistencies in the task leading to large between-period fluctuations of within-patient baseline values. Change from baseline in MDS-UPDRS-III score with PF-06412562 resulted in a placebo-adjusted point estimate of -10.59 with a one-sided 90% upper CI of PF-06412562 versus placebo model-based contrast of (-inf, -7.44) at 1.5-2.5 h after the dose (p < 0.0001). All adverse events were mild-to-moderate.

Conclusions: We report the first evidence of potential anti-parkinsonian efficacy of the oral selective D1/D5 partial agonist PF-06412562 without the significant acute changes in cardiovascular parameters reported with previous D1 agonists.