None approved; Baliforsen in Phase 1/2
Myotonic dystrophy type 1 (DM1) is the most common muscular dystrophy in adults, affecting approximately 1 in 8,000 people worldwide. It is caused by an expansion of the CTG trinucleotide repeat in the 3′ untranslated region (3′-UTR) of the DMPK gene. Normal individuals have 5–37 CTG repeats; affected individuals have 50 to several thousand. The disease is autosomal dominant with variable expressivity and anticipation (increasing severity in successive generations as the repeat expands).
DM1 is a multisystemic disease with symptoms that include myotonia (delayed muscle relaxation), progressive muscle weakness, cataracts, cardiac conduction defects, insulin resistance, and cognitive impairment. Disease severity generally correlates with repeat length — congenital DM1 (with thousands of repeats) is the most severe form, causing severe hypotonia and respiratory failure at birth.
The disease mechanism in DM1 is unique among trinucleotide repeat disorders. The expanded CTG repeat is transcribed into mRNA containing an expanded CUG repeat, which forms hairpin structures that sequester RNA-binding proteins, particularly muscleblind-like (MBNL) proteins, in nuclear foci. The sequestration of MBNL proteins disrupts alternative splicing of hundreds of downstream target genes, causing a global mis-splicing phenotype that underlies the multisystemic symptoms.
This RNA gain-of-function mechanism makes DM1 amenable to ASO therapy through degradation of the toxic expanded-repeat RNA. ASOs designed as gapmers can target the DMPK mRNA for RNase H-mediated degradation, eliminating the toxic CUG-repeat RNA and releasing sequestered MBNL proteins to restore normal splicing patterns.
Avidity Biosciences is developing Baliforsen, an antibody-ASO conjugate that targets DMPK mRNA in skeletal muscle. The antibody component delivers the ASO specifically to muscle cells, addressing a key challenge in DM1 treatment — achieving sufficient ASO concentration in the affected tissues. Baliforsen is in Phase 1/2 clinical trials.
Ionis Pharmaceuticals previously advanced IONIS-DMPKRx, a conventional ASO targeting DMPK mRNA, but development was discontinued due to insufficient target reduction in muscle tissue — highlighting the delivery challenge that antibody-conjugate approaches are designed to overcome.
Pequliar designs gene-silencing ASO candidates for DM1, targeting the DMPK transcript for RNase H-mediated degradation. The platform identifies optimal binding sites, scores candidates for thermodynamic properties and off-target safety, and provides synthesis-ready sequences with full chemistry assignment. While the delivery challenge in DM1 is significant, the sequence design principles remain critical — an effective ASO must first bind its target with high affinity and specificity before any delivery strategy can succeed.
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Start a designPequliar is a computational research tool for informational purposes only. All sequences are computationally predicted candidates that have not been experimentally validated. Pequliar does not prescribe, recommend, or administer any compound. Independent validation by qualified professionals is required.