A Study of Safety and Tolerability of Fipamezole in Adult Subjects With Parkinson's Disease Who Are Receiving Levodopa

Inclusion Criteria: 1. Subject is a man or woman between 30 and 75 years of age, inclusive, with intact oral mucosa at Screening (Visit 1) and Randomization (Visit 2). 2. Subject has a diagnosis of idiopathic Parkinson's disease defined according to the UK Parkinson's Disease Society Brain Bank Clinical Diagnosis criteria. 3. Subject has been receiving a stable regimen of at least three daily administrations of levodopa (with a peripheral dopa decarboxylase inhibitor), with no dose changes for at least 4 weeks prior to Randomization (Visit 2). 4. Subject is rated at stage 2 to 4 on the Hoehn and Yahr scale. 5. If currently taking other medications (other than levodopa), subject must be on a stable regimen, defined as no dose changes for at least 1 month prior to Randomization (Visit 2). 6. Subject demonstrates the ability to comprehend the study procedures and provide informed consent. 7. Female subjects must be either postmenopausal for at least 1 year or surgically sterilized at least 3 months prior to Randomization (Visit 2). Male subjects must either be sterile or willing to use 2 approved methods of contraception when engaged in sexual intercourse with a female partner from Randomization (Visit 2) until 30 days after the last dose of study drug. 8. Subject has an upper arm circumference of not less than 24 cm and not more than 42 cm for both arms. Exclusion Criteria: 1. Subject participated in an investigational medication study within the 3 months prior to Randomization (Visit 2). 2. Subject has immediate family members who are site Investigators or sponsor employees. 3. Subject has a history or presence of clinically significant cardiovascular, pulmonary, hepatic, renal, hematologic, gastrointestinal, endocrine, immunologic, dermatologic, neurologic, or oncologic or any other condition that, in the opinion of the Investigator, would jeopardize the safety of the subject or the validity of the study results. 4. Subject has impaired renal function (defined as a creatinine level of ≥ 1.5 times the upper limit of normal) at Screening (Visit 1). 5. Subject has impaired hepatic function (defined as SGOT/AST or SGPT/ALT levels ≥ 1.5 times the upper limit of normal) at Screening (Visit 1). 6. Subject has second- or third-degree atrioventricular block or sick sinus syndrome, atrial fibrillation, atrial flutter, severe or unstable angina, congestive heart failure, or myocardial infarction within 3 months of the screening visit or a significant ECG abnormality, including a QRS \> 110 msec, a PR interval \> 230 msec, a QTc ≥ 450 msec for male subjects, or a QTc ≥ 470 msec for female subjects. 7. Subject has a history of risk factors for Torsades de Pointes, including unexplained syncope, known long QT syndrome, or a clinically significant abnormal laboratory assessment such as hypokalemia, hypercalcemia, or hypomagnesemia. Subjects with a family history of long QT syndrome or Brugada syndrome will also be excluded. 8. Subject is at immediate risk of requiring hospitalization. 9. Subject has significant tremor or dyskinesia which, in the opinion of the Investigator, might interfere with reliable assessment of continuous Holter ECG and ABPM. 10. Subject has, in the opinion of the Investigator, a clinically important abnormality on his/her physical examination, electrocardiography, vital sign measurements, or laboratory assessment. 11. Subject is being treated with a disallowed medication that cannot be discontinued prior to Randomization (Visit 2) (See Table 6). 12. Subject has a current diagnosis of substance abuse or history of alcohol or drug abuse in the past 2 years prior to Screening (Visit 1). 13. Subject has positive findings on urine drug screen at Screening (Visit 1). 14. Subject has an allergy to fipamezole or its excipients.