ARTHEx Biotech Files for IPO: University-Originated Oligonucleotide Therapy ATX-01 Targets Unmet Needs in Myotonic Dystrophy Type 1

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PharmaCircle monitoring shows: ARTHEx Biotech is a clinical-stage biotechnology company headquartered in Valencia, Spain, dedicated to developing precise gene expression regulation.Targeted RNA TherapeuticsThe company's proprietary platform combines highly selective oligonucleotides with tissue-specific delivery technology, effectively targeting skeletal muscle, heart, and brain.

Its leading projectATX-01Being evaluated in the Phase I/IIa ArthemiR clinical trial for the treatment of rare neuromuscular diseases——Myotonic Dystrophy1Type (DM1）Based on this, ARTHEx is advancing its drug pipeline targeting high unmet medical needs in areas such as muscles, the central nervous system, heart, and lung diseases.

In fact, ARTHEx Biotech is a Spanish company.University of Valencia (University of Valencia）A spin-off company co-founded in 2019 by genetics professor Rubén Artero and Dr. Beatriz Llamusí.

Beatriz Llamusí and Rubén Artero
Source: University of Valencia

At the time, the Translational Genomics Research Team at the University of Valencia discovered that: In muscle biopsy samples from patients with myotonic dystrophy type 1 (DM1) and in various disease animal models, a class of microRNAs (small RNAs that can bind to mRNA and inhibit protein synthesis) that suppress the expression of MBNL proteins (Muscleblind-like proteins) were significantly upregulated. Based on this finding, the researchers tested anti-miR oligonucleotides (anti-miRs) targeting these microRNAs in preclinical mouse models. The results showed that anti-miRs effectively increased MBNL protein levels, reduced nuclear aggregates formed by toxic DMPK mRNA, corrected aberrant splicing events, and improved myotonia symptoms and enhanced grip strength in the mouse model.

The research results were published in 2018 in《Nature Communications》, with the patent application completed by the University of Valencia and subsequently licensed to ARTHEx Biotech. This discovery not only unveils a new dimension in the pathogenesis of Myotonic Dystrophy Type 1 (DM1) but also lays the scientific foundation for ARTHEx Biotech's core candidate drug, ATX-01.

Myotonic Dystrophy Type 1 (DM1) is a highly disablingRare diseases with autosomal dominant inheritance, with over 1 million patients globally, isThe most common hereditary muscular dystrophy in adults. This disease not only affects skeletal muscles but also involves multiple systems, leading to respiratory dysfunction, extreme fatigue, hypersomnia, arrhythmia, severe gastrointestinal issues, as well as cognitive and behavioral disorders. Although it most commonly manifests in adulthood, it can also occur at birth (congenital) or during childhood. As the condition progresses, patients experience a significant decline in daily living abilities, and life expectancy is notably reduced.There are currently no approved disease-modifying therapies., there is an urgent need for breakthrough solutions in clinical practice.

ATX-01 is aOleic Acid-Coupled AntimiROligonucleotideDrug, which can be preferentially delivered to target tissues (muscle and brain), aims to suppressMicroRNA-23b（miR-23b）——This molecule is a natural inhibitor of MBNL protein expression. In DM1 patients, the loss of MBNL protein function is caused by two mechanisms: (1) reduced MBNL protein expression due to the upregulation of miR-23b; (2) MBNL protein being "captured" by toxic DMPK mRNA, leading to splicing abnormalities (spliceopathy), which is the root cause of clinical symptoms in DM1 patients.

ARTHEx Biotech has confirmed that ATX-01 can inhibit miR-23b, therebyPromoteMBNLProtein levels, while reducing nuclear aggregation and toxicityDMPK mRNALevel. This highly differentiatedDual Mechanism of ActionSignificantly increased the level of free MBNL protein, improved splicing abnormalities, and ultimately restored function in animal models.

On July 28, 2020, ARTHEx Biotech announced the completion of a €6.95 million seed financing round to advance the development of its RNA therapies. The funding includes: an initial investment of €2.7 million from Invivo Ventures and the Spanish Center for the Development of Industrial Technology (CDTI) through the Innvierte program; an additional €4.25 million in new financing from Invivo Ventures and France’s Advent France Biotechnology (AFB).

Since then, the company has successively received multiple research grants and innovation awards, providing crucial support for its early R&D and team building.

Since 2023, ARTHEx Biotech has been throughTwo Rounds of B-Series Financing, and fully advance the clinical development of its core candidate drug ATX-01 in myotonic dystrophy type 1 (DM1), while expanding its RNA-targeted drug pipeline.

In February 2024, ATX-01 received IND approval from the U.S. FDA, and in October 2024, ARTHEx Biotech announced that the first patient had been dosed in the Phase I/IIa clinical trial ArthemiR. It is reported that ATX-01 is an industry...The first one used forDM1Anti-microRNATherapeutic Drugs。

MoEntropy Medical Data

On May 3, 2023, ARTHEx Biotech announced the completion of a €42 million Series B financing round. The round was led by Columbus Venture Partners, with new investors including the European Innovation Council (EIC) Fund, Hadean Ventures, and Sound Bioventures; existing investors Invivo Capital, AdBio Partners, and the Spanish Center for Industrial Technical Development (CDTI) participating through the Innvierte program also continued to follow up.

The proceeds from this financing will be used to advance the company’s core candidate drug, ATX-01, into Phase I/IIa clinical trials for the treatment of Myotonic Dystrophy Type 1 (DM1).

Following this round of financing, Dr. Frédéric Legros, former Chairman of the Board of ARTHEx Biotech SL, officially assumed the role of Chief Executive Officer (CEO) to strengthen clinical and commercial leadership.

Dr. Frédéric Legros joined ARTHEx as Executive Chairman in November 2022, after serving as Chief Operating Officer (COO) of Dynacure, a company he co-founded in 2016. Prior to founding Dynacure, Dr. Legros was Vice President and Head of Corporate Business Development at Valneva SE, a publicly listed biotechnology company in France, from 2008 to 2016.

On September 17, 2025, ARTHEx Biotech announced the completion of an expanded Series B financing round, with the addition of new investor Bpifrance bringing the total amount raised in this round to $87 million.

This B-round extension financing was jointly led by Large Venture under Bpifrance and InnoBio investment strategies, and received continuous support from all existing shareholders, including AdBio Partners, CDTI Innovación (through its Innvierte program), Columbus Venture Partners, the European Innovation Council (EIC), Hadean Ventures, Invivo Partners, and Sound Bioventures.

The proceeds from this financing will be used to accelerate the global clinical development of ARTHEx Biotech's leading candidate drug ATX-01 for Myotonic Dystrophy Type 1 (DM1), including the ongoing interventional Phase I/IIa ArthemiR clinical study, as well as an open-label extension study in preparation for subsequent registrational clinical trials.

As of now, ATX-01 has received orphan drug designation from the U.S. FDA and the European Medicines Agency (EMA) for the treatment of DM1, and it has also been granted Rare Pediatric Disease designation by the FDA. According to disclosures, the company expects to release the first human clinical data in 2026.

MoEntropy Medical Data

In addition to the aforementioned research, ARTHEx is simultaneously advancing ATX-01 inMyotonic Dystrophy2Type(DM2) and the most severeCongenitalDM1(Congenital DM1) is currently in the preclinical research stage. In addition, ARTHEx Biotech SL is leveraging its proprietary platform to expand a new generation of drug candidates.ATX-03, exploring its therapeutic potential in muscle-related diseases, with specific indications not disclosed.

From a startup idea by two scientists at the University of Valencia Science Park in 2019, to gaining multinational capital support and advancing global clinical trials by 2025 — the growth trajectory of ARTHEx Biotech SL perfectly illustrates the "patent-incubation-financing-clinical" paradigm of academic translation. We look forward to ATX-01 — this innovative therapy derived from RNA science — changing the life trajectory of DM1 patients in the future.

Public information shows that companies involved in the research and development of drugs for myotonic dystrophy also include:Avidity Biosciences (acquired by Novartis), Dyne Therapeutics, AMO Pharma, Sarepta Therapeutics, Arrowhead Pharmaceuticals, PepGen, Entrada Therapeutics, EditForce, Hengrui Medicine, Jiajin Bio, etc.

References:

MoEntropy Pharma Data pharma.bcpmdata.com (formerly Pharma Intelligence Cloud Data);

https://www.arthexbiotech.com/post/arthex-biotech-upsizes-series-b-financing-round-to-87m-to-advance-lead-program-atx-01-in-myotonic-dystrophy-type-1-and-expand-pipeline-of-targeted-rna-medicines；

https://www.arthexbiotech.com/our-approach-focus；

https://www.uv.es/uvweb/college/en/profile/a-university-valencia-research-spin-gets-investment-test-myotonic-dystrophy-therapy-humans-1285950309813/Novetat.html?id=1286141232638；

Other relevant public information (images in the text are from the official company, unless otherwise noted).

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