A Two Part Study (306A/306B) to Assess Droxidopa in Treatment of NOH in Patients With Parkinson's Disease

Systolic blood pressure is transiently and minimally decreased in healthy individuals upon standing. Normal physiologic feedback mechanisms work through neurally-mediated pathways to maintain the standing blood pressure, and thus maintain adequate cerebral perfusion. The compensatory mechanisms that regulate blood pressure upon standing are dysfunctional in subjects with orthostatic hypotension (OH), a condition that may lead to inadequate cerebral perfusion with accompanying symptoms of syncope, dizziness or lightheadedness, unsteadiness and blurred or impaired vision, among other symptoms. Orthostatic hypotension may be a severely disabling condition which can seriously interfere with the quality of life of afflicted subjects. Currently available therapeutic options provide some symptomatic relief in a subset of subjects, but are relatively ineffective and are often accompanied by severe side effects that limit their usefulness. Support garments (tight-fitting leotard) may prove useful in some subjects, but is difficult to don without family or nursing assistance, especially for older subjects. Midodrine, fludrocortisone, methylphenidate, ephedrine, indomethacin and dihydroergotamine are among some of the pharmacological interventions that have been used to treat orthostatic hypotension, although only midodrine is specifically approved for this indication. The limitations of these currently available therapeutic options, and the incapacitating nature and often progressive downhill course of disease, point to the need for an improved therapeutic alternative. Symptomatic OH in patients with Parkinson's disease is thought to be a consequence of norepinephrine depletion leading to low systolic blood pressure (SBP) and cerebral-hypoperfusion (reduced blood flow to the brain). Therapy with droxidopa results in increased levels of norepinephrine which should lead to improved SBP and cerebral perfusion thereby reducing the signs and symptoms of NOH. The present study will evaluate the clinical benefit in NOH patients with PD treated with droxidopa compared to those treated with placebo. Participation in the study will last a maximum of 14 weeks consisting of a 2 week (maximum) screening/baseline period; a 2 week (maximum) double-blind dose titration; an 8 week double-blind placebo-controlled treatment period; and a 2 week follow-up period. An extension study is also available to continue treatment if determined appropriate by the study doctor. This Study is NCT01132326 sponsored by Chelsea Therapeutics and is enrolling by invitation only. Droxidopa: Droxidopa \[also, known as L-threo-3,4-dihydroxyphenylserine, L-threo-DOPS, or L-DOPS\] is the International non-proprietary name (INN) for a synthetic amino acid precursor of norepinephrine (NE), which was originally developed by Sumitomo Pharmaceuticals Co., Limited, Japan. It has been approved for use in Japan since 1989. Droxidopa has been shown to improve symptoms of orthostatic hypotension that result from a variety of conditions including Shy Drager syndrome (Multiple System Atrophy), Pure Autonomic Failure, and Parkinson's disease. There are four stereoisomers of DOPS; however, only the L-threo-enantiomer (droxidopa) is biologically active. Stereoisomers and enantiomers are compounds that have the same chemical elements; however, they may react differently as the elements are positioned in different locations. The exact mechanism of action of droxidopa in the treatment of symptomatic NOH has not been precisely defined; however, its NE replenishing properties with concomitant recovery of decreased noradrenergic activity are considered to be of major importance. Droxidopa has been marketed in Japan since 1989. Data from clinical studies and post-marketing surveillance programs conducted in Japan show that the most commonly reported adverse drug reactions with droxidopa are increased blood pressure, nausea, and headache. In clinical studies, the prevalence and severity of droxidopa adverse effects appear to be similar to those reported by the placebo control arm.