ARTHEx Biotech, a clinical-stage biotechnology company developing targeted RNA medicines for rare genetic neuromuscular disorders, announced the successful closing of its upsized Series B financing round totaling $87 million. The extension financing was led by new investor Bpifrance, with renewed participation from all existing shareholders including AdBio Partners, CDTI Innovación, Columbus Venture Partners, European Innovation Council (EIC), Hadean Ventures, Invivo Partners and Sound Bioventures.
Advancing ATX-01 Through Clinical Development
The proceeds will primarily support the global clinical development of ARTHEx's lead program, ATX-01, for Myotonic Dystrophy Type 1 (DM1). This includes advancing the ongoing interventional Phase I/IIa ArthemiR™ study and preparing for an open-label extension to support a registrational study.
ATX-01 represents a novel therapeutic approach as an anti-miR oligonucleotide designed to inhibit microRNA23b (miR-23b), which acts as a natural repressor of MBNL protein expression. In DM1 patients, loss of MBNL protein function occurs through two mechanisms: reduced expression of MBNL proteins due to miR-23b upregulation, and MBNL sequestration in toxic DMPK mRNA, which leads to spliceopathy and causes the symptomatology observed in DM1 patients.
Dual Mechanism of Action Shows Promise
By inhibiting miR-23b, ARTHEx has demonstrated that ATX-01 increases MBNL production and decreases foci formation and toxic DMPK mRNA. This highly differentiated dual mechanism of action leads to a significant increase of free MBNL, improving splicing abnormalities and ultimately restoring function in animal models.
In human DM1 myoblast cell lines obtained from patients with a wide range of CTG repeat lengths, ATX-01 increased MBNL protein expression and significantly reduced toxic DMPK mRNA, correcting critical molecular defects such as spliceopathy. Beneficial effects were also observed in both the HSALR and DMSXL mouse models, demonstrating molecular and functional improvements.
Regulatory Recognition and Clinical Progress
ATX-01 has received Orphan Drug Designation for DM1 from both the US FDA and European authorities, as well as Rare Pediatric Disease (RPD) Designation from the FDA. The ArthemiR™ study is a randomized, placebo-controlled, double-blind single and multiple ascending dose study evaluating ATX-01 in adults with DM1.
Industry Investment and Future Outlook
Laurent Higueret, Deputy Director at Bpifrance's Large Venture Fund, stated: "We believe ATX-01 could be a game-changer for patients suffering from DM1 on the basis of novel science and impressive data generated so far. We are excited to partner with ARTHEx as the company reaches clinical proof-of-concept stage and look forward to supporting Frederic and team in their efforts to build a leading franchise of precision RNA medicines."
Benoit Barteau, Investment Director at Bpifrance's InnoBio funds, added: "The approach developed by ARTHEx for DM1 aiming at targeting miR-23b has demonstrated compelling in vitro and in vivo results. The dual mechanism of action of ATX-01 offers real potential to be the best-in-class treatment for DM1. In addition, the Company's delivery platform enables uptake into multiple tissues affected by DM1, allowing ATX-01 to go beyond the muscle, treating the whole disease and not just the symptomatology. We are eager to see initial clinical data in 2026."
Expanding Pipeline Beyond DM1
Frédéric Legros, Chairman and CEO, commented: "This financing marks an important milestone for ARTHEx and underscores the strength of our approach in DM1 and our emerging delivery platform, with its potential to deliver nucleic acid-based therapies beyond muscle. We are well positioned to advance ATX-01 toward a registrational study for DM1, while continuing to expand our pipeline across areas of high unmet need in muscular, CNS, cardiac conditions."
The funding will also support the advancement of ARTHEx's broader pipeline of targeted RNA medicines across areas of high unmet need in muscular, CNS, and cardiac conditions. The company's proprietary platform pairs selective oligonucleotides with tissue-specific delivery to reach skeletal muscle, heart, and brain.
