Oligonucleotides are small nucleic acids capable of interacting with DNA or RNA to modulate gene expression. Widely used by researchers as research tools to modulate the expression of the genes they seek to decipher the function, oligonucleotides can also serve as therapeutic agents to regulate targets of interest. After the first marketing authorisation of an oligonucleotide therapeutics in 1998, the field met little clinical success until 2016 when Spinraza® became the first drug authorized for spinal muscular atrophy. This compound became in the following years the first "blockbuster" among this class of molecules, validating the commercial potential of oligonucleotide drugs. Since then, about ten other oligonucleotides hit the market and a broad pipeline is currently in late clinical development. Through our article, we describe therapeutic oligonucleotides, their modes of action and their patentability.