A fully 2′-O-methyl-phosohorothioate(2′-O-Me-PS) modified (CAG)7 ASO complimentary to (CUG)n repeats has previously been shown to effectively silence DMPK1 trinucleotide repeat expansion transcripts in a DM1 humanized animal model and human DM1 cell system and to reduce the number of DM1-associated RNA foci in a repeat-length-dependent manner.23, 24 We therefore tested whether transfecting with 2′-O-Me-PS-(CAG)7 ASOs, complimentary to TCF4 CTG18.1-derived transcripts, could induce a similar reduction in CUG-specific RNA foci, a biomarker of CTG18.1-related pathology, in the CEC cultures. The gene discussed is TCF4; the disease is myotonic dystrophy type 1.