Besides prominent approaches using oligonucleotides,[15] several groups have reported small molecules binding to the CUG repeats and modulating the splicing pattern in DM1 cells.[16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29] We here report that the dimeric form of 1,3‐diaminoisoquinoline derivative JM642 (Figure 1) rescued the mis‐splicing in Ldb3 pre‐mRNA in the DM1 cell model and Clcn1 and Atp2a1 pre‐mRNAs in DM1 mouse model in a dose‐dependent manner. This evidence concerns the gene ATP2A1 and myotonic dystrophy type 1.