Fragile X Clinical Trial of New PDE4D Inhibitor from Tetra

With a $200,043 grant from FRAXA Research Foundation, Dr. Elizabeth Berry-Kravis completed a successful Phase 2 clinical trial of a new PDE4 inhibitor for adult men ages 18-45 with Fragile X syndrome.

Elizabeth M. Berry-Kravis, MD, PhD
Principal Investigator

Tetra Discovery Partners & Rush University Medical Center
2018-2020 FRAXA Research Grant

With support from the Pierce Family Fragile X Foundation

FRAXA Research Foundation has funded a Fragile X clinical trial of an investigational new drug, led by Dr. Elizabeth Berry-Kravis at the Rush University Medical Center in Chicago. This trial is treating 30 males, 18-45 years of age who have Fragile X syndrome, with a new PDE4D allosteric inhibitor from Tetra Discovery Partners using a crossover design, so that everyone gets active drug for part of the time and placebo for part of the time.

PDE4 - Potential Fragile X Treatment Target

This study is a major advance in clinical research for a number of reasons. First, the enzyme phosphodiesterase 4 (PDE4), which breaks down the signaling molecule cyclic AMP, has been singled out as a promising treatment target for a long time. It was first proposed before FRAXA Research Foundation existed, when Dr. Berry-Kravis found low levels of cAMP in Fragile X patients. She notes, “this trial will bring my earliest work on Fragile X syndrome, showing abnormal cyclic AMP signaling in FXS, to fruition, with a treatment trial directed at correcting the mechanism I discovered in 1990 when in my Child Neurology fellowship.”

Indeed, many researchers have shown that PDE4 inhibitors can fix Fragile X-related problems in animal models. Most recently, FRAXA researchers (including FRAXA Medical Director, Dr. Michael Tranfaglia, and FRAXA-DVI Director, Dr. Patricia Cogram) in collaboration with Dr. Mark Gurney of Tetra Discovery Partners showed that this new compound showed powerful rescue effects in Fragile X mice, which persisted long after the drug was discontinued (

Tetra Discovery Partners

Tetra Discovery Partners

Until now, no PDE4 inhibitors were available for us to use in Fragile X clinical trials. In part, this is because most drug companies have been interested in other much larger indications for these drugs, like Alzheimer Disease. There is still a great deal of interest in these blockbuster indications, but FRAXA has forged a close collaboration with Tetra Discovery Partners, a small biotech company based in Michigan. Tetra has developed an advanced PDE4D allosteric inhibitor which is highly selective, non-toxic, and easy to take (it doesn’t have the side effect of GI upset that most other drugs in this class have). While Tetra is also developing this drug for Alzheimer’s, they agreed to branch out into Fragile X.

As Dr. Gurney notes, “Dr. Berry-Kravis’ research gives us hope that BPN14770 may address a core biochemical change in Fragile X patients. The results of our collaborative preclinical studies with the FRAXA Research Foundation in the Fragile X mice are very promising. We look forward to initiating the Phase 2 clinical trial that will be conducted by Dr. Berry-Kravis with support from the FRAXA Research Foundation. Tetra Discovery Partners has a patient-focused culture that meshes perfectly with the passion of FRAXA Research Foundation and the dedication of Dr. Berry-Kravis to the care of her patients.”

Tetra has announced that the FDA has granted Orphan Drug Designation to BPN14770 for treatment of Fragile X syndrome.

Advanced Clinical Trial Design

One interesting aspect of this study is that the crossover design, with every participant taking active drug for half of the trial period, will allow us to look for the same kind of “carry-over effects” in the Fragile X patients that were observed in the Fragile X mice. Trial subjects will also receive a full therapeutic dose of the drug, so clinically meaningful responses are possible. Most importantly, this trial will use state-of-the-art objective cognitive and physiologic outcome measures, including eye-tracking and measuring brain-wave responses to sounds, a major step forward from previous studies of investigational compounds.

We are excited about this new clinical trial, and we look forward to developing a new therapeutic option for Fragile X! We are grateful to the Pierce Family Fragile X Foundation for contributing funds toward this project.

Explore Current Fragile X Research

FRAXA-funded researchers around the world are leading the way towards effective treatments and ultimately a cure.

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