Pharmacological Tolerance in the Treatment of Fragile X Syndrome

Pharmacological Tolerance in the Treatment of Fragile X Syndrome

With a $90,000 grant from FRAXA Research Foundation, Dr. Patrick McCamphill and Dr. Mark Bear at Massachusetts Institute of Technology (MIT) will further investigate drug tolerance and ways to overcome it. 

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Mechanisms of Tolerance to Chronic mGluR5 Inhibition

Mechanisms of Tolerance to Chronic mGluR5 Inhibition

Over the past few years, both Novartis and Roche sponsored large-scale clinical trials of metabotropic glutamate receptor 5 (mGlu5) negative allosteric modulators (NAMs) to treat Fragile X syndrome (FXS). With a $90,000 grant from FRAXA Research Foundation in 2015-2017, Dr. Mark Bear’s team will explore if mGlu5 NAMs dosed chronically causes tolerance, and if so, how it develops and to probe new avenues to prevent or circumvent it.

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Did Tolerance Result in Fragile X mGluR5 Clinical Trial Failures?

Did Tolerance Result in Fragile X mGluR5 Clinical Trial Failures?

Although the clinical trials failed to show efficacy in the patient population and Novartis and Roche discontinued their Fragile X development programs, Dr. Senter has worked with Mark Bear, PhD to carefully review parent observations. Those caregiver reports suggested tolerance to mGlu5 antagonists antagonists developed quickly, consistent with some preclinical findings in the mouse model.

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Why Did Fragile X Clinical Trials of mGluR Antagonists Fail?

Why Did Fragile X Clinical Trials of mGluR Antagonists Fail?
Drug Tolerance and Dose Range Problems May Have Been the CulpritsAndy Tranfaglia and his dad, Mike Tranfaglia In my opinion, the Fragile X clinical trials of AFQ056 sponsored by Novartis failed because of a dose range that was inadequate for Fragile X, and because of the unexpected development of tolerance. Dosage problems are relatively easy to correct, but tolerance to the degree we observed may be a kind of fatal flaw, at least if we're talking about mGluR5 antagonists.  The mGluR Theory of Fragile X is still probably correct; it's just that no one (least of all Novartis) expected tolerance to this drug -- indeed, I'm not sure they would agree that's what happened. I think we saw a much better response than most people because our son, Andy, was also on minocycline, effectively augmenting the response, and perhaps delaying the development of tolerance.  This may be a clue to understanding the mechanism of tolerance,Read more