The molecular basis of DM1 spliceopathy

Myotonic dystrophy type 1 is an autosomal dominant disorder caused by a CTG trinucleotide repeat expansion in the 3′ untranslated region of the DMPK gene, with repeat lengths ranging from 50 to more than 3,500 in affected individuals. The resulting mutant CUG-expanded (CUGexp) transcript does not produce a toxic protein — instead, it accumulates in nuclear foci and sequesters muscleblind-like (MBNL) splicing factors, a mechanism consistently described across retrieved patent filings as “RNA dominance.” The downstream consequence is pervasive spliceopathy across skeletal muscle, cardiac, and CNS tissues.

Two downstream splice junctions serve as the field’s primary pharmacodynamic biomarkers: SERCA1 (sarcoplasmic/endoplasmic reticulum calcium ATPase 1) exon 22 inclusion and m-Titin exon 5 inclusion in tibialis anterior, gastrocnemius, and quadriceps muscles. Restoration of these splice events after treatment is cited as evidence of MBNL rescue across multiple patent families from University of Rochester, Ionis Pharmaceuticals, and Astellas Gene Therapies. According to OMIM, DM1 is the most common adult-onset muscular dystrophy, underscoring the scale of unmet medical need that this pipeline is attempting to address.

ASO and PPMO approaches: the dominant patent cluster

Antisense oligonucleotides targeting the DMPK CUGexp transcript constitute the largest cluster in the DM1 patent landscape, with at least 15 distinct records spanning University of Rochester, Ionis Pharmaceuticals, and Genzyme Corporation. Two mechanistically distinct ASO chemistries have been pursued: RNase H-mediated cleavage of the mutant transcript (the gapmer approach championed by Ionis and Rochester) and steric blocking of MBNL sequestration sites on the CUGexp RNA.

The University of Rochester’s foundational work — filed as a WO application in 2012 with Wheeler and Thurman as named inventors — established that modified oligonucleotides can preferentially reduce CUGexp DMPK RNA while preserving some wild-type DMPK expression, a selectivity property that has remained a design goal across subsequent filings. Ionis Pharmaceuticals subsequently filed an actively pending IL application in 2021 broadly covering modified oligonucleotides with DM1 treatment claims, consistent with an active IND or clinical-stage program. According to patent data reviewed by PatSnap, this Rochester-to-Ionis IP lineage represents the clearest academic-to-commercial transfer in the DM1 field.

Genzyme Corporation (a Sanofi subsidiary) pursued a chemically distinct route: cationic peptide-linked morpholino (PPMO) oligonucleotides targeting the poly-CUG repeat tract in the DMPK 3′ UTR. Filed across IL, AU, and MX jurisdictions between 2015 and 2019, the Genzyme PPMO approach uses the peptide linkage to enhance systemic distribution and muscle cell penetration — a differentiated delivery strategy compared to the gapmer/RNase H mechanism. A Genzyme filing explicitly noted that “there is currently no clinically available therapeutic agent targeting the toxic RNA,” contextualising the unmet need that motivated this chemistry investment.

“There is currently no clinically available therapeutic agent targeting the toxic RNA — the primary pathological driver of this disease.” — Genzyme Corporation patent filing, 2015

Muscle-targeted delivery: the translational frontier

Dyne Therapeutics represents the most translationally advanced program in the retrieved dataset, based on the clinical specificity of its 2025 WO patent filing. The company’s platform covalently links a DMPK-targeting gapmer ASO to a muscle-targeting agent — specifically an anti-transferrin receptor 1 (TfR1) antibody — that binds an internalising cell surface receptor on muscle cells, driving selective intracellular delivery to both skeletal and cardiac muscle.

Dyne’s filing cluster spans SG (2021), IL (2023), BR (2024), and WO (2025), reflecting an active international IP prosecution strategy. The 2025 WO filing is the most clinically informative document in the dataset: it specifies that the antibody-oligonucleotide conjugate is intended to address myotonia, fatigue, gastrointestinal symptoms, cognitive impairment, mobility impairment, upper extremity function, swallowing, and breathing — all domains measurable by the Myotonic Dystrophy Health Index (MDHI), a validated patient-reported outcome instrument used in clinical trials. This level of clinical endpoint specification strongly suggests that this program is at or approaching clinical study.

The fundamental delivery challenge that Dyne’s TfR1-antibody conjugate attempts to solve is well-established: naked oligonucleotides distribute poorly to muscle tissue after systemic administration, limiting the pharmacodynamic effect achievable in the primary disease tissue. By exploiting transferrin receptor 1-mediated endocytosis — a pathway highly active in metabolically demanding muscle cells — the conjugate platform aims to achieve the muscle concentrations required for meaningful spliceopathy correction. This approach is consistent with broader trends in oligonucleotide conjugate development documented by Nature and tracked by patent offices including the EPO.

AAV-RNAi gene therapy and splice correction readouts

Two separate gene therapy programs targeting DM1 appear in the retrieved patent dataset, both using recombinant adeno-associated virus (rAAV) vectors to deliver RNAi molecules against DMPK. Genzyme Corporation filed rAAV-RNAi patents in AU and BR in 2025, representing a strategic pivot from its earlier PPMO chemistry. In parallel, Astellas Gene Therapies filed a WO application in 2024 describing AAV-delivered nucleic acids for DM1 correction.

The Astellas filing is notable for its explicit splice correction readout: an increase in SERCA1 mRNA containing exon 22 following treatment is specified as a primary success signal. This exon 22 inclusion metric is consistent with a biomarker strategy suitable for IND-enabling or Phase 1 studies, as it provides an objective, tissue-level pharmacodynamic measure that can be assessed in muscle biopsies. The convergence of multiple programs on SERCA1 exon 22 inclusion as a shared endpoint suggests that the field is moving toward standardised biomarker criteria for DM1 clinical trials.

Genzyme’s dual-platform IP strategy — holding both PPMO (2015–2019) and rAAV-RNAi (2025) patent clusters for DM1 — signals sustained commitment to the indication across modalities. The parallel advancement of both approaches by the same assignee may reflect competitive IP positioning rather than a commitment to a single therapeutic platform, as the rAAV-RNAi approach offers the potential for durable effect from a single administration, while PPMO requires repeated dosing. Standards bodies including WHO have highlighted the regulatory complexity of gene therapy products, which may influence the relative commercial timelines of these two Genzyme approaches.

MicroRNA modulation and MSI2 small molecule inhibition

Two mechanistically distinct approaches from Universitat de Valencia target the DM1 spliceopathy phenotype indirectly — without directly degrading the CUGexp DMPK transcript. Both represent early-preclinical IP with lower competitive crowding than the dominant ASO cluster, making them potentially attractive entry points for academic spinouts or differentiated biotech programs.

AntagomiR-mediated MBNL restoration

A 2021 US patent from Universitat de Valencia describes inhibitors of microRNAs that repress MBNL1 and/or MBNL2 as a DM1 therapeutic strategy. The preferred targets are miR-23b-3p and miR-218-5p — two microRNAs whose inhibition is proposed to increase endogenous MBNL1/MBNL2 protein levels, thereby partially rescuing the spliceopathy phenotype downstream of CUGexp RNA sequestration. The filing covers oligoribonucleotide antagomiRs with chemical modifications for enhanced in vivo stability, cell penetration, and tissue distribution in skeletal muscle, heart, and CNS. This approach is mechanistically complementary to direct CUGexp degradation: rather than removing the sequestering RNA, it attempts to replenish the sequestered protein.

MSI2 small molecule inhibition

A 2022 WO filing (with a 2025 US application pending) from Universitat de Valencia identifies MSI2 (Musashi homolog 2) as an RNA-binding protein whose activity is pathologically elevated in DM1 cells. The filing describes both oligonucleotide inhibitors of MSI2 and a specific small molecule — a 2,3,4,10-tetrahydro-7,10-dimethyl-2,4-dioxobenzo[g]pteridine derivative — as MSI2 functional inhibitors. In vivo experiments in HSALR transgenic mice are referenced, including AAV9-mediated MSI2 overexpression as a comparator to demonstrate the pathological role of MSI2 in the disease phenotype.

The MSI2 inhibitor approach is notable because it represents a chemically tractable, orally administrable target class — small molecules — in a field dominated by oligonucleotide modalities that require injection and face significant delivery challenges. The identification of a specific benzo[g]pteridine derivative as an MSI2 inhibitor with in vivo activity in HSALR mice provides a starting point for medicinal chemistry optimisation. The patent data reviewed through PatSnap Eureka indicates this IP space remains relatively uncrowded compared to the DMPK ASO cluster.

Strategic landscape: IP crowding, biomarkers, and white space

The DM1 patent landscape is characterised by a dominant central target (DMPK CUGexp RNA), an emerging delivery differentiation race, and mechanistically distinct peripheral IP spaces that remain relatively uncrowded. Commercial patent filings constitute more than 90% of DM1-relevant retrieved results, with academic literature signals embedded in patent backgrounds rather than as standalone publications.

IP crowding around DMPK ASOs

Ionis Pharmaceuticals’ actively pending IL 2021 filing broadly covers modified oligonucleotides with DM1 treatment claims. This patent estate could create freedom-to-operate (FTO) constraints for competing ASO developers, particularly those building on the gapmer/RNase H mechanism. IP strategists should conduct FTO analysis against the Ionis/Rochester filing family before advancing any conventional DMPK-targeting ASO program toward IND filing.

Dyne Therapeutics as potential first-mover

Based on retrieved signals, Dyne Therapeutics’ muscle-targeted antibody-oligonucleotide conjugate represents the most advanced and recently filed IP in this dataset. The 2025 WO filing’s specification of MDHI clinical domains — covering myotonia, fatigue, GI symptoms, cognitive impairment, mobility, upper extremity function, swallowing, and breathing — indicates that clinical protocol design is actively underway. The anti-TfR1 targeting mechanism addresses the primary delivery limitation of naked oligonucleotides in muscle tissue and, if validated clinically, could establish a platform applicable beyond DM1 to other muscle diseases.

White space: MSI2 and miRNA approaches

MSI2 inhibition and miRNA antagomiR approaches (miR-23b-3p and miR-218-5p) represent mechanistically distinct IP spaces with lower competitive crowding in this dataset. These could be attractive entry points for academic spinouts or biotech companies seeking differentiated DM1 positions, particularly if combined with validated delivery technologies. The combination of MSI2 inhibitors with MBNL-restoring antagomiRs is a logical but unreported direction in retrieved data, representing a potential combination strategy hypothesis for future research programs.

Preclinical infrastructure: organ-on-a-chip

Erasmus University Medical Center Rotterdam (WO 2025) describes an organ-on-a-chip platform for neuromuscular disease with shRNA-based gene knockdown in contractile skeletal muscle, applicable to DM1 drug screening. This enabling technology signals maturation of preclinical infrastructure for DM1 drug discovery and may accelerate the translation of emerging modalities — including MSI2 inhibitors and antagomiRs — through the preclinical validation stage. Regulatory frameworks for such novel screening platforms are being developed by agencies including the FDA under its Modernization Act provisions for non-animal testing methods.