Following the robust targeting efficiency of CasRx in our HEK293T transient overexpression model, we wanted to determine whether these gRNAs and CasRx can successfully target endogenous C9orf72 sense and antisense repeat transcripts in C9orf72 ALS/FTD patient-derived iPSC-neurons. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.