GRAND RAPIDS, MI, USA I July 12, 2022 I Tetra Therapeutics, a Shionogi Group Company, focused on the development of compounds for the treatment of brain disorders associated with cognitive and memory deficits, today announced the initiation of three Phase 2b/3 clinical studies of the investigational drug BPN14770 (zatolmilast) as a potential treatment for Fragile X Syndrome (FXS), the most common genetic form of autism. A selective small molecule inhibitor of phosphodiesterase‐4D (PDE4D), BPN14770 has shown positive results in a previous Phase 2 study in FXS in adult males (Berry-Kravis EM, et al. Inhibition of phosphodiesterase-4D in adults with fragile X syndrome: a randomized, placebo-controlled, phase 2 clinical trial. Nat Med. 2021;27(5):862-870.). BPN14770 has also received Orphan Drug Designation from the U.S. Food and Drug Agency (FDA) for the potential treatment of FXS.

The Phase 2b/3 studies comprise two separate 150 subject, randomized, double-blind, placebo-controlled studies: one in an adolescent male population (ages 12-17), one in an adult male population (18-45), and a third open label extension study open to patients in both populations at the conclusion of the primary study. Endpoints for the studies include cognitive and behavioral assessments of the efficacy of BPN14770 by a variety of standard tests and determinations of the experimental drug’s safety and tolerability. The study will also gather pharmacokinetic data on BPN14770. The studies are being conducted at multiple sites across the United States lead by principal investigator Elizabeth M. Berry-Kravis, M.D., Ph.D. at Rush University Medical Center, Chicago, Illinois. The studies are expected to be conducted over the next two years. Additional information is available through (Identifiers: NCT05163808, NCT05358886, NCT05367960).

“We are excited to initiate these pivotal trials with BPN14770 in patients with Fragile X Syndrome, and are hopeful that the results of these studies will enable us to seek approval from FDA,” said Chad Coberly, JD, Chief Executive Officer of Tetra Therapeutics.

“We are anxious to get started with these studies that offer hope for people living with Fragile X Syndrome and their caregivers,” said Dr. Elizabeth Berry-Kravis, pediatric neurologist, Rush University Medical Center, and principal investigator. “Given our previous positive results with BPN14770 in the phase 2 study, we are hopeful these studies at a larger scale will show similar results. I find it exciting that we have a drug that potentially corrects a core deficit in FXS, a decrease in cAMP, that has been documented in patients as well as in the fly and mouse models of the disorder.”

About BPN14770

BPN14770 is an investigational new drug that selectively inhibits phosphodiesterase-4D to enhance early and late stages of memory formation. Preclinical animal models show that BPN14770 has the potential to promote the maturation of connections between neurons, which is impaired in patients with FXS, and to protect connections between neurons which otherwise are lost in patients with Alzheimer’s Disease. Tetra has completed investigational Phase 2 studies of BPN14770 in adults with FXS and in Alzheimer’s disease. BPN14770 also has received Orphan Drug Designation from the U.S. Food and Drug Administration (FDA).

About Tetra Therapeutics

Tetra Therapeutics, a Shionogi Group Company, is a clinical stage biotechnology company focused on developing a portfolio of therapeutic products to people suffering from Fragile X Syndrome, Alzheimer’s disease, traumatic brain injury, and other brain disorders. Tetra Therapeutics is headquartered in Grand Rapids, Michigan. For more information, please visit the company’s website at

About Shionogi

Shionogi & Co., Ltd. is a 143-year-old global, research driven pharmaceutical company headquartered in Osaka, Japan, that is dedicated to bringing benefits to patients based on its corporate philosophy of “supplying the best possible medicine to protect the health and wellbeing of the patients we serve.” The company currently markets products in several therapeutic areas including anti-infectives, pain, CNS disorders, cardiovascular diseases and gastroenterology. S hionogi’s research and development currently target two therapeutic areas: infectious diseases, and pain/CNS disorders.

For more information on Shionogi & Co., Ltd., please visit

SOURCE: Tetra Therapeutics