Described herein is an intronic recognition element for splicing modifier (iREMS) that can be recognized by a small molecule splicing modifier compound of Formula (I) provided herein or a form thereof, wherein W, X, A and B are as defined herein. In one aspect, methods for modifying RNA splicing to modulate the amount of a product of a gene, wherein a precursor RNA transcript transcribed from the gene that contains an intronic REMS is modified utilizing a splicing modifier compound of Formula (I), are described herein. In another aspect, methods for modifying RNA splicing to modulate the amount of an RNA transcript or protein product encoded by a gene, wherein a precursor RNA transcript transcribed from the gene is modified to comprise an intronic REMS utilizing a splicing modifier compound of Formula (I), are described herein.
