The mainstay drug, levadopa, is 40 years old, and merely addresses the symptoms of Parkinson's.

FORBES: Andy Grove Puts Millions Into Parkinson's Fight

During the first ten weeks of their treatment each was either given Mirapex or levadopa at the maximum tolerated dose.

BBC: Parkinson's drug breakthrough

Yet the mainstay drug, levadopa, which stimulates the brain to produce more dopamine, is 40 years old and provides only symptomatic relief.

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Several months later Grove began taking the minimum dose of levadopa.

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From then the Mirapex patients continued to take a fixed dose of the drug, while levadopa was given to all patients in differing doses depending on their symptoms.

BBC: Parkinson's drug breakthrough