In TTR-mediated familial (or hereditary) amyloidosis, the heart and nervous system are most commonly affected. Without intervention, the survival rate ranges between 5-15
years from the onset of the disease.
Since most of the abnormal proteins are produced in the liver, transplanting the liver can allow for the production of normal TTR. Waiting periods for organ donation are frequently long, but transplantation is a viable option for some patients whose disease is not too far advanced.
Meanwhile, new drugs are being developed to prevent familial amyloid deposits from forming in the first place. As with liver transplantation, evidence shows that by reducing
the abnormal protein available to become amyloid, organ function can improve. Two such drugs that may prevent the mutant TTR from misfolding into amyloid are diflunisal and tafamidis. These small molecules bind to the precursor proteins and stabilize their structure, so that they do not form amyloid fibrils and accumulate in the body.
A separate class of drugs using “gene silencing” techniques heralds a revolution in ATTR treatment. These therapies utilize the body’s natural process for regulating gene expression.
Very briefly, here is how it works. In our cells, the genes coding for proteins are transcribed from DNA into messenger RNA (mRNA) molecules. These mRNA are then translated by our cells’ machinery to produce all of the proteins that make life possible. With gene-silencing therapy, small RNA-like molecules are carried in the blood to the liver. Once in the cells,
the RNA-based drugs are able to bind specifically with the mRNA that would produce TTR proteins. When the drugs bind with the target mRNA, special cellular enzymes (nucleases) will break down and recycle the mRNA. Therefore, TTR amyloid production could be slowed or stopped at the source.