Effectiveness of Continuous Dopamine Therapies in Parkinson’s Disease: A Review of How L-DOPA Works in the Body and Brain

Levodopa, a key treatment for Parkinson’s disease, often faces absorption issues in the brain and digestive system, has a short duration, and loses effectiveness over time, requiring higher doses as the disease progresses. This leads to inconsistent symptom control, according to a study by Inbrain Pharma, which is developing a form of dopamine delivered directly to the brain. While continuous delivery of levodopa helps reduce some of these limitations, it still doesn’t provide complete control of symptoms. There remains a significant need for treatments that better mimic the brain’s natural dopamine production. Dr. Caroline Moreau, Inbrain's clinical scientific adviser, emphasized that the “medical needs in managing Parkinson’s disease remain very great.” The study, published in the Journal of Parkinson’s Disease, reviewed 75 articles, focusing on 10 that analyzed levodopa’s pharmacokinetics (movement through the body) and pharmacodynamics (effectiveness in the body). Researchers found that levodopa's challenges include poor absorption, rapid loss from the body, and an inability to fully convert to dopamine as Parkinson’s advances. Existing continuous delivery methods, like subcutaneous and enteral approaches, improve symptom control but do not eliminate issues such as dyskinesia (involuntary movements). In response, Inbrain has developed A-dopamine, which is delivered directly to the brain via a pump and catheter. Early results from a clinical trial (DIVE-I) show that A-dopamine is both safe and effective at controlling severe symptoms, while allowing for reduced oral levodopa doses. Patients experienced fewer tremors, slowness, pain, and involuntary movements, improving their quality of life. The researchers conclude that most levodopa delivery methods still have significant limitations, highlighting the need for new strategies like direct dopamine administration.