A range of experimental treatments for Parkinson's are also being researched, and some of these research areas include:

 Cell Transplant Therapy

 Gene Therapy

 Growth Factor Delivery

These procedures and their side-effects are discussed below.

10.1 Cell Transplant Therapy

The surgical transplant of fetal substantia nigra cells has been performed in several hundred patients to date in multiple centers throughout the world.
The results for this procedure have been encouraging for some patients, but two recent double-blind placebo-controlled studies showed that consistent benefit was only seen in young Parkinson's patients (age 60 or below), and side-effects were significant in some patients.
For example, some patients developed off-medication dyskinesias (uncontrolled movements) even without any levodopa or other dopaminergic medication.

The lack of consistently good results and the significant side-effects encountered indicate that further research – particularly in animals - is needed.

Another cell transplant technique that shows some promise is the use of retinal pigment epithelial cells. These cells are derived from tissue at the back of the eye, and they produce and release dopamine. An open-label trial in six advanced Parkinson's patients has shown promise, and further trials and research are underway.

10.2 Gene Therapy

Gene Therapy has currently been tried in only a few Parkinson's patients to date, and the procedure is still highly experimental.
While experiments in animals with Parkinson's have shown promise, further research is needed.

10.3 Growth Factor Delivery

Glial Cell-Derived Neurotrophic Factor (GDNF) stimulates the growth of new dopamine producing neurons in animals.

In initial trials with a small number of patients, direct delivery of GDNF to the brain produced promising results. However, in recent larger trials, the treatment failed to produce the same high levels of results.

Further research is needed, especially regarding how to improve delivery of growth factors to the correct targets in the brain.