Oligonucleotide therapeutics are chemically modified nucleic acids with novel mode of actions and distinct pharmacokinetic properties in comparison to classical small molecules. There are 3 main classes: antisense oligonucleotides (ASO), splice switching oligonucleotides (SSO) and the short interference RNA (siRNA). They act on the RNA level with various mechanism of action in order to correct defective protein expression that causes the disease.