Parkinson's Disease Overview

Parkinson’s disease (PD) is the second most common neurodegenerative disease behind Alzheimer’s disease. PD is a chronic, progressive neurodegenerative disease that results from the death of certain neurons in an area of the brain called the substantia nigra that controls movement. These neurons are responsible for producing dopamine, an essential brain signaling chemical, or neurotransmitter, that enables smooth, coordinated movements of both voluntary and involuntary muscles throughout the body. The lack of dopamine in patients with PD renders them unable to regulate motor control, producing characteristic symptoms including tremor at rest, rigidity (stiffness), slowness of movement (bradykinesia) and impaired balance and walking, as well as significant non-motor disturbances, including mood disorders, sleep impairment, fatigue, bowel and bladder dysfunction and dementia. By the time of PD diagnosis, approximately 60% to 80% of the dopamine producing cells have died.

Over one million people in the United States and between four and six million people worldwide suffer from PD. There is no known cure or disease modifying treatment currently available for PD. Current medications and treatments only control the major symptoms of the disease, with most drugs becoming less effective over time as the disease progresses. Current drugs and therapies either aim to supplement dopamine levels in the brain, mimic the effect of dopamine in the brain by stimulating dopamine receptors, referred to as dopamine agonists, or prevent the enzymatic breakdown of dopamine, prolonging its effect. The standard of care for the treatment of symptoms of PD remains oral levodopa, a drug approved nearly 50 years ago. While oral levodopa is efficacious, there are significant challenges for physicians in creating a dosing regimen of oral levodopa that consistently maintains levodopa levels within a patient’s therapeutic range. Over time, the response to levodopa becomes less reliable and less predictable. As a result, the majority of PD patients experience OFF episodes despite taking PD medications.