FDA Grants Rare Pediatric Designation to ARTHEx Biotech's ATX-01 for Myotonic Dystrophy Type 1

VALENCIA, Spain, Nov. 7, 2024 -- ARTHEx Biotech S.L., a biotechnology firm in the clinical stages of developing new treatments by modifying gene expression, has announced that the U.S. Food and Drug Administration (FDA) has awarded Rare Pediatric Designation (RPD) to its drug ATX-01. This drug is aimed at addressing myotonic dystrophy type 1 (DM1), a rare neuromuscular condition. ARTHEx had already obtained Orphan Drug Designation (ODD) for ATX-01 from both the U.S. and European regulatory bodies for DM1.

ATX-01 is an antimiR oligonucleotide that works by inhibiting microRNA 23b (miR-23b), a natural suppressor of MBNL protein production. In DM1 sufferers, the lack of MBNL protein functionality, which results from both reduced MBNL protein levels due to miR-23b upregulation and MBNL sequestration in toxic DMPK mRNA, induces a spliceopathy leading to the symptoms observed in DM1 patients.

Research using human DM1 myoblast cell lines derived from patients with varying CTG repeat lengths showed that ATX-01 increased MBNL protein expression and significantly decreased toxic DMPK mRNA, thus correcting critical cellular defects like spliceopathy. Currently, ATX-01 is in the Phase I-IIa clinical trial named ArthemiR™ for DM1 treatment.

The compound, an oleic acid-conjugated antisense oligonucleotide, is designed to preferentially target muscle and brain tissues. Its mechanism, which includes boosting MBNL protein levels and reducing toxic DMPK mRNA, along with its capability to cross the blood-brain barrier in animal models, makes it suitable for treating different DM1 forms, from congenital to adult stages.

DM1 manifests in several phenotypes: Congenital DM1, Childhood DM1, Adult or Classic DM1, and Mild or Late Onset DM1. Pediatric forms often have more CTG repeats, present symptoms earlier, and exhibit a different phenotype, especially with more brain-related symptoms, compared to adult DM1. Severe and potentially fatal manifestations of DM1 typically affect children and adolescents more.

Judith Walker, M.D., Chief Medical Officer of ARTHEx, remarked, "Myotonic Dystrophy Type 1 is a severe and hard-to-treat neuromuscular disorder impacting not just adults but children as well, with no approved treatments available for any age group. By leveraging its dual mechanism of action to elevate MBNL protein levels and diminish toxic DMPK mRNA, and its efficient delivery to muscle and brain in animals, we believe ATX-01 has the potential to be a best-in-class treatment for DM1. Our Orphan Drug Designations in the US and Europe, coupled with this Rare Pediatric Disease Designation, enhance and expand our development plans for ATX-01 across the DM1 spectrum."

Under U.S. regulations, a "rare pediatric disease" is defined as one that is serious or life-threatening, predominantly affecting individuals from birth to 18 years old, and is rare as per U.S. law. The FDA's Rare Pediatric Disease (RPD) designation is intended to encourage sponsors like ARTHEx to develop drugs for children with rare diseases. One major benefit of the RPD designation is the ability to apply for a Priority Review Voucher (PRV) if specific conditions are fulfilled.

ARTHEx Biotech, headquartered in Valencia, Spain, is a clinical-stage biotechnology company focused on developing innovative medicines through gene expression modulation. Their lead investigational drug, ATX-01, is being tested for myotonic dystrophy type 1 in the Phase I-IIa ArthemiR™ trial. ARTHEx is also working on identifying and developing microRNA modulators for other diseases with high unmet medical needs, including genetically-driven conditions like DM1.