Rare Pediatric, Orphan Drug Status Granted to DepYmed’s Rett Therapy

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by Vanda Pinto, PhD |

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The U.S. Food and Drug Administration (FDA) has granted rare pediatric disease and orphan drug designations to DepYmed’s orally available small molecule PTP1B-inhibitor therapy being developed to treat Rett syndrome.

According to DepYmed, a Phase 1 clinical trial is planned for later this year to investigate what the company describes as its “leading” candidate for treating the condition.

“FDA’s decision to grant these designations for our lead clinical candidate for the treatment of Rett Syndrome is a significant achievement for DepYmed,” Andreas Grill, DepYmed’s president and CEO, said in a press release.

“Further, it perfectly aligns with our mission to provide treatments for patients where few if any options exist and highlights the urgent need to develop a treatment for patients with Rett Syndrome,” Grill said.

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Rare pediatric disease designation is given to experimental therapies that seek to treat rare or life-threatening disorders that mainly affect patients younger than 18. After receiving this status, companies whose medications are approved may be eligible for a priority review voucher for a different product.

Orphan drug status is granted to speed up the development of investigational treatments for diseases affecting fewer than than 200,000 people in the U.S. The status offers benefits, including FDA fee exemptions, tax credits for clinical studies, and seven years of marketing exclusivity in the U.S., if approval is granted.

Almost all Rett syndrome cases are caused by disease-causing mutations in the MECP2 gene on the X chromosome. The MECP2 gene carries instructions for a protein with the same name, which is important for the function of and communication between brain cells.

MECP2 also controls the activity of other genes. For example, preclinical studies have shown that the PTP1B gene is a direct target of MECP2 and that PTP1B protein levels are increased in fibroblasts — connective tissue cells — from patients with Rett syndrome.

Studies also showed that small-molecule PTP1B inhibitors restored normal cell signaling and eased Rett-like symptoms in mice, including behavioral and motor skill deficits. These findings were the scientific basis for the development of DepYmed’s therapy for Rett.

Although previous attempts to develop successful PTP1B-inhibitor therapies were challenging, the company states that it’s the first to generate a proprietary portfolio of PTP1B inhibitors, which are orally bioavailable.

DepYmed also discovered a new type of small molecule to potentially treat Wilson disease — a rare genetic disorder that causes copper to build up in the liver, brain, and other tissues. The company’s efforts in developing new treatments has been conducted in collaboration with Cold Spring Harbor Laboratory.