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Feb
03

A rare disease a day: Hunter Syndrome

February is a pretty big month for several reasons. First there is the World Symposium 2014 in San Diego (Feb 10-13) which focuses on Lysosomal Storage Diseases (LSDs). Then at the end of the month is the NIH rare disease day (Feb 28). I will be attending these events and presenting posters.

So in honor of this I wondered if I could try to post something on rare diseases each day as time permits. At the weekend I read an article in the Boston Globe about a young boy called Jack Fowler who was refused compassionate use of a drug from Shire. Jack has Hunter Syndrome or MPS II in which a deficiency or absence of the enzyme iduronate-2-sulfatase (I2S) results in the build up of  glycosaminoglycans or GAG.

Shire has a drug Idursulfase (elaprase) which is an enzyme replacement therapy for Hunter syndrome that brings in >$ 375,000 per patient/year and is in additional clinical trials. For example it was recently shown to be safe and well tolerated in children under 5. It was also shown to not affect growth patterns. A major problem with the enzyme replacement therapy is getting it to the brain. And a few years ago a mouse study was published on a fusion protein that enabled the enzyme to get in the brain at levels 100 fold over the  protein on its own. So clinical studies getting the fusion protein into the brain of patients like Jack are the likely only hope.

It appears there are very  few papers in Pubmed relating to small molecules efforts to treat the disease, e.g. chaperones. Yet I did find an interesting paper from 2012 that shows how the very common food additive carrageen acts as an inhibitor of iduronate sulfatase in cells in vitro. Obviously it is unclear whether there is a similar effect in vivo. The structure of carrageen also is reminiscent of endogenous galactose or N-acetylgalactosamine-containing glycosaminoglycans (GAGs), chondroitin sulfate (CS), dermatan sulfate (DS), and keratan sulfate which makes you wonder whether it could have a role in other MPS diseases. So should a Hunter patient avoid foods with this additive? Who knows? But it makes you wonder how many potential other molecules in our diets could have similar effects or be potentially protective. It remains to be seen whether anyone is even looking at such possibilities in vitro. Perhaps the connections have yet to be made. Could there be potential treatments already out there? I am reminded at this point of Glucosamine being a chaperone in vitro for Sanfilippo syndrome (MPSIIIC).

 

 

 

 

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  1. Elaine Crowley says:

    Hi
    I’m looking on your website trying to find a poster
    I can put up on my Facebook page to show awareness for
    Rare chromosome day.. My son has a rare chromosome
    Called inverted duplication and deletion of 8p
    I’m just wondering if you can help me at all..
    Many thanks
    Elaine Crowley

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