The present invention relates to antisense oligonucleotides for modulating the activity of glycine decarboxylase (GLDC). In particular, the present invention relates to antisense oligonucleotides capable of inducing exon skipping of RNA. Also claimed are pharmaceutical compositions, kits and methods of treating cancer and inducing exon-skipping using said antisense oligonucleotides. In addition, a method for aiding the categorising or determining prognosis of a cancer or in selecting a therapeutic strategy for a patient with cancer, based on assessing the level of GLDC nucleic acid, protein or activity in a sample derived from the patient is provided.
