ARTHEx Biotech Delivers Multiple Presentations at IDMC-15 Highlighting Clinical Progress of ATX-01 and Mechanistic Insights for Myotonic Dystrophy Type 1 (DM1) and 2 (DM2)

VALENCIA, Spain, May 27, 2026 /PRNewswire/ -- ARTHEx Biotech, a clinical-stage biotechnology company advancing RNA-based therapeutics for neuromuscular disorders, today announced multiple presentations at the 15th International Myotonic Dystrophy Consortium (IDMC-15) meeting, taking place in Saguenay, Canada, May 26-30, 2026.  The presentations showcased the clinical progress of ATX-01 in the ongoing ArthemiR™ study and new mechanistic insights for DM1 and DM2.

"We are very encouraged by the continued progress of the ArthemiR™ study and the growing body of study data on ATX-01," said Frédéric Legros, Executive Chairman and Chief Executive Officer of ARTHEx Biotech. "Together, these presentations highlight both the clinical advancement of our lead program and the strength of our underlying science. Importantly, they reinforce our belief that targeting miR-23b has the potential to deliver meaningful, disease-modifying benefit across the multisystem manifestations of myotonic dystrophy. For the first time, we are excited to present data supporting the potential of this approach in Myotonic Dystrophy Type 2, extending the reach of our platform beyond DM1 and opening a new avenue for patients with significant unmet need."

At IDMC-15, ARTHEx delivered a presentation on clinical progress with ATX-01, its investigational antimiR therapy designed to inhibit miR-23b to address the underlying RNA-driven pathology of DM1. A second presentation highlights the dual mechanism of action of ATX-01, including upregulation of MBNL protein expression and reduction of toxic DMPK RNA, leading to improved splicing regulation. A third presentation extends this work into Myotonic Dystrophy Type 2 (DM2), where ATX-01 demonstrated restoration of MBNL1 protein levels and improvement in disease-associated splicing abnormalities.

Details of the ARTHEx Presentations:

Poster #101: Preliminary data from the first-in-human ArthemiR study of a novel antimir drug, ATX-01, for the treatment of DM1

Authors: Guillaume Bassez, Judith Walker, Nikki McIntyre, Barbara Collins, Estefanía Lucendo, Georgina Butler, Isabella Castano, Lucía Solaz, Lilian Chow, Diego Piqueras, Estefanía Cerro, Beatriz Llamusí, Julia Presanis, on behalf of the ArthemiR Study Investigators

ATX-01 is a novel anti-microRNA in clinical development for the treatment of Myotonic Dystrophy (DM). ATX-01 has a dual mechanism of action as a result of the inhibition of miR-23b, a key player in DM1 pathophysiology. In preclinical experiments, ATX-01 increases translation of the important RNA binding protein MBNL and decreases levels of toxic DMPK RNA foci, leading to an improvement in mis-splicing events characteristic of DM1.

ArthemiR™ is a first-in- human randomized, double-blind, placebo-controlled clinical study to assess the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary clinical efficacy of ascending single and multiple doses of ATX-01 in adult participants with DM1. The study is an integrated single- ascending dose (Part 1) and multiple-ascending dose (Part 2) trial in participants with DM1 aged 18 to 64 years old. The study is ongoing at 12 sites across Canada, France, Italy, the Netherlands, Spain, the UK, and the US.

Summary of findings:

• ATX-01 at single doses is safe and well tolerated, at the first 2 dose levels tested.
• No DLTs were observed at the first 2 dose levels, nor to date, at dose level 3.
• ATX-01 continues to be evaluated in the ArthemiR™ trial.
• Further data including analyses of the muscle biopsies (CASI-22, MBNL levels, DMPK levels), will be reported at the end of Part 1 (SAD).

Poster #129: New insights into DM1 mechanism of pathogenesis: DMPK, MBNL and miR-23b balance as the master key of DM1 pathology

Authors: Diego Piqueras-Losilla, Argimiro Mayoral-Olmos, Andrea García-Rey, Ana Díaz-Maqueda, Nuria Barquero, Rubén Artero, Beatriz Llamusí, Estefanía Cerro-Herreros.

Affiliations: ARTHEx Biotech; University Institute of Biotechnology and Biomedicine (BIOTECMED); Translational Genomics Group, Incliva Biomedical Research Institute; CIBERER ISCIII

miR-23b is significantly upregulated in muscle biopsies from DM1 patients and positively correlates with CTG repeat length in blood. In vitro, expression of expanded CUG repeats induces miR-23b upregulation, AgomiR-23b-mediated overexpression in control fibroblasts differentiated into myotubes exacerbates DM1-associated splicing defects. Transcriptomic and Sylamer analyses in DM1 fibroblasts differentiated to myotubes identify widespread deregulation of miR-23 target genes, with functional enrichment showing that 150 out of 207 altered biological processes are associated with miR-23 activity, predominantly linked to muscle development and function.

Summary of findings:

• miR-23b is upregulated in DM1 and contributes to disease pathogenesis beyond MBNL1 repression, promoting widespread molecular alterations associated with muscle dysfunction.
• ATX-01 exerts a dual mechanism of action by simultaneously restoring MBNL1 expression/function and promoting nuclear export and cytoplasmic degradation of toxic DMPK RNA through correction of MBNL1 isoform balance.
• Altogether, compared with direct DMPK-targeting approaches, ATX-01 provides broader molecular rescue, supporting restoration of MBNL activity as a key determinant of splicing correction and therapeutic benefit in DM1.

Poster #130: Targeting miR-23b uncovers a therapeutic opportunity for Myotonic Dystrophy Type 2

Authors: Estefanía Cerro-Herreros, Diego Piqueras-Losilla, Dulce Peris-Moreno, Argimiro Mayoral-Olmos, Bjarne Udd, Alberto García-Martín, Irene Gonzalez-Martinez, Rubén Artero, Ariadna Bargiela, Beatriz Llamusí

Affiliations: ARTHEx Biotech; University Institute of Biotechnology and Biomedicine (BIOTECMED); Translational Genomics Group, Incliva Biomedical Research Institute; CIBERER ISCIII; Neuromuscular Center, Tampere University Hospital; Department of Neurology, Vaasa Central Hospital

Myotonic Dystrophy Type 2 is a multisystemic neuromuscular disease caused by the expansion of CCTG repeats within intron 1 of the CNBP gene, leading to the accumulation of toxic intronic RNA, sequestration of MBNL proteins into nuclear foci, and widespread splicing dysregulation. Despite sharing key pathogenic mechanisms with Myotonic Dystrophy Type 1, there are currently no approved or clinically developed therapies for DM2.

Summary of findings:

• ATX-01-mediated inhibition of miR-23b restores MBNL-dependent RNA processing in Myotonic Dystrophy Type 2 primary and immortalized cells.
• In primary cells this leads to correction of multiple disease-associated splicing defects and improved processing of the mutant CNBP transcript.
• Importantly, these molecular rescue effects occur without altering overall CNBP expression, supporting a favorable therapeutic profile.
• Together, these findings provide an initial proof of concept for antimir-23b therapy in DM2 and support further evaluation in additional DM2 cellular models and future preclinical studies.

About ARTHEx Biotech

ARTHEx Biotech is a clinical-stage company developing targeted RNA medicines designed to precisely modulate gene expression. Its proprietary platform, BOOST-ON™, pairs selective oligonucleotides with enhanced tissue delivery to reach skeletal muscle, heart, and brain. Its lead program, ATX-01, is in clinical evaluation for myotonic dystrophy type 1 (DM1), a rare neuromuscular disorder, in the Phase I/IIa ArthemiR™ trial. Building on this foundation, ARTHEx is advancing a pipeline of therapies for additional areas of high unmet need across muscular, CNS and cardiac diseases.

The Company headquarters are in Valencia, Spain.

For more information on ArthemiR™, please visit https://www.arthemir.com or https://clintrials.gov.  For more information, please visit www.arthexbiotech.com and engage with us on LinkedIn. 

SOURCE ARTHEx Biotech