Table 5.

Summary.

There is a long list of failed clinical studies that have been based on preclinical models with exogenous neurotoxins.

A possible explanation for these failures is that preclinical models based on exogenous neurotoxins do not represent what happens in the neurodegenerative process of the disease.

The degenerative process of dopaminergic neurons that contain neuro-melanin is an extremely slow process that takes years where the therapeutic effects of drugs that have failed in clinical studies were measured in very rapid and expansive preclinical models cannot be observed.