MDM4-targeting ASO sodium is a 25mer antisense oligonucleotide targeting? MDM4. MDM4-targeting ASO sodium induced exon 6 skipping, leading to nonsense-mediated decay of the mRNA transcript that excludes exon-6. In multiple human melanoma cell lines and in melanoma patient-derived xenograft (PDX) mouse models, MDM4-targeting ASO-mediated skipping of exon 6 decreased MDM4 abundance, inhibited melanoma growth, and enhanced sensitivity to MAPK-targeting therapeutics.