The effect of JM608 and JM642 on alternative splicing was investigated on pre‐mRNA of the Ldb3 gene in the C2C12 DM1 cell model conditionally expressing r(CUG)800 repeat RNA.[37] (Figure 2 a) In the control cells without expression of r(CUG)800, the percentage of exon 11 exclusion in the Ldb3 gene was about 81±1.7 %, while the fraction in the DM1 cell model expressing r(CUG)800 was 53±1.9 % (Figure 2 b). Here, LDB3 is linked to myotonic dystrophy type 1.