Examples of non-selective gapmer ASOs include elsunersen, currently in phase 3 clinical trials for SCN2A gain-of-function (GoF) developmental and epileptic encephalopathy (OMIM: #613721)9, and tofersen, which is approved for the treatment of SOD1-associated amyotrophic lateral sclerosis (ALS, OMIM #105400).10 Conversely, allele-selective gapmers have been developed for conditions such as FUS-ALS (OMIM #608030), where the ASO jacifusen selectively targets the pathogenic c.1574C>T (p.Pro525Leu) variant.11 This evidence concerns the gene SCN2A and amyotrophic lateral sclerosis.