Antisense therapy is a form of treatment for genetic disorders or infections. When the genetic sequence of a particular gene is known to be causative of a particular disease, it is possible to synthesize a strand of nucleic acid (DNA, RNA or a chemical analogue) that will bind to the messenger RNA (mRNA) produced by that gene and inactivate it, effectively turning that gene "off". This is because mRNA has to be single stranded for it to be translated. Alternatively, the strand might be targeted to bind a splicing site on pre-mRNA and modify the exon content of an mRNA.
This synthesized nucleic acid is termed an "anti-sense" oligonucleotide (AON) because its base sequence is complementary to the gene's messenger RNA (mRNA), which is called the "sense" sequence (so that a sense segment of mRNA " 5'-AAGGUC-3' " would be blocked by the anti-sense mRNA segment " 3'-UUCCAG-5' ").
Antisense oligonucleotides have been researched as potential drugs for diseases such as cancers (including lung cancer, colorectal carcinoma, pancreatic carcinoma, malignant glioma and malignant melanoma), diabetes, amyotrophic lateral sclerosis (ALS), Duchenne muscular dystrophy, spinal muscular atrophy, Ataxia-telangiectasia and diseases such as asthma, arthritis and pouchitis with an inflammatory component. As of 2016, several antisense drugs have been approved by the U.S. Food and Drug Administration (FDA): fomivirsen as a treatment for cytomegalovirus retinitis, mipomersen for homozygous familial hypercholesterolemia, eteplirsen for Duchenne muscular dystrophy, and nusinersen for spinal muscular atrophy.