A biotech company called Alnylam announced today that a small clinical trial for a genetic therapy based on RNA interference, or RNAi, suggests that the technique can have a powerful effect on its target gene. The therapeutic effect lasted for over a month with just one dose. The company is also working with a medical device maker, Medtronic, on a way to deliver RNAi treatment directly to the brain, in order to treat the degenerative brain disease Huntington's.

The patients in the trial have a genetic disorder that originates in the liver and leads to the buildup of protein deposits in many organs. Alnylam, a Cambridge, Massachusetts-based company, says its RNAi therapeutic, given at its highest dose, reduces the amount of the faulty protein that spurs the disease by almost 94 percent.

The positive results add weight to the notion that RNAi therapeutics could eventually help patients with a range of genetic diseases. RNAi therapy involves researchers producing snippets of RNA, a close relative of DNA, that match a portion of a gene of interest. When administered, this so-called small interfering RNA (siRNA) causes the destruction of that gene's products before it can be turned into a protein. The specificity of RNAi for targeting particular genes has attracted a lot of interest from people who want to use it as a clinical treatment (see "Prescription RNA").