There are plenty of examples of drugs that have been repurposed in recent years. For instance, thalidomide, the initially prescribed medication for headache in pregnant women which led to countless numbers of babies born with body malformations during the 50s and 60s, now this drug is used for treating certain types of cancer, such as myelomas. Another example would be the cardiovascular protection provided by the all common aspirin, a pain medication with “good” side effects.
A very recent possibility was introduced by a study in The Lancet, where 30 patients of Parkinson’s disease were treated weekly with an anti diabetic drug, exenatide, for over 48 weeks, while other 30 patients received a placebo instead. After the end of the test period, those patients on the anti diabetes drug fared much better than their counterparts in motor tests. Interestingly, 12 weeks later this motor improvement was still maintained in comparison to placebo controls.
This study is of interest because this randomised, double-blind, placebo-controlled trial proves that the symptoms of Parkinson could be potentially diminished with a common drug already approved to market, and part of the daily treatments of many old patients. Therefore, the target population might benefit from the positive side-effects of their base anti diabetes treatments. Also, since the drug has already gone through all the necessary health and safety controls, access to it would be much faster and easier than with a newly developed drug.
In the treatment of diabetes type 2, exenatide exerts its effects by stimulating insulin release in the pancreas via specific receptor activation. Interestingly, the same sort of receptors are found in the brain, and are related to dopamine function. Dopamine cell destruction is a landmark of Parkinson’s disease and the reason for the associated motor deficits, therefore the causal link of the symptomatic improvement of Parkinson’s patients with exenatide might lay in this shared receptor identity.
Of course there are BUTs to this study. Like the authors point out, patients did not report a significant improvement of their day-to-day life in comparison with current standard of care, and there is no proof as to whether exenatide causes any changes to disease progression. In principle, it would seem that the effects are only symptomatic. Therefore, despite the apparent advantages of drug repurposing, more research is needed before applying this drug to Parkinson’s. In any case, it is always good news to learn about more uses to drugs, and the interactive pathways operating in our bodies.