Almost as challenging as the search for new medications in Parkinson's is the need to target such medications to their site of action. It's no use having a drug that acts on the right receptors but has no means of reaching them. Efficacy is only meaningful in the context of access.

Most of the drugs used in Parkinson's act in the brain and, in order to reach their site of action, must cross the blood brain barrier (BBB). This is a given. Yet there are many drugs which do not cross the BBB and complex strategies involving direct injection into the brain are needed.This has certainly been the case for some of the larger molecules, such as peptides like Glial Derived Neurotrophic Factor (GDNF).

But an inability to penetrate the BBB is not simply the province of these giant molecular titans. Many small molecules, by virtue of charge, polarity or structure, also fail to cross the BBB. Sometimes these are similar molecules to those already available as medicines. Imagine if these molecules, normally stopped at the gates, could somehow sneak through under the cloak of another molecule.

Sound like science fiction? Actually not. A group at the Mayo Clinic led by Robert Jenkins have developed a synthetic peptides carrier to do just such a thing. The peptide in essence acts as a cloak, binding to proteins in the blood and, in combination, being transported in the brain.

This carrier system appears to work. The team have tested it with seven different drugs, mostly chemotherapeutic agents. Whether the system will allow the accumulation of enough drug to be effective perhaps remains to be seen. But the system certainly shows promise. A case for guarded optimism I would say.

Jon Stamford

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