Washington

A much-hyped technology known as RNA interference (RNAi) has moved a step closer to the clinic.

Biotechnology firm Acuity Pharmaceuticals of Philadelphia, Pennsylvania, asked for permission on 10 August to use the technique to treat a common cause of blindness. The clinical trial, if approved by the US Food and Drug Administration, would be the first of its kind.

RNAi, which uses short lengths of genetic material to selectively shut off genes, was demonstrated in human cells in 2001 and has yet to be tested in people. Some studies have raised concerns about just how selective the technique is, so observers say the filing is a landmark for the field but remain cautious.

“This is a significant milestone,” says Greg Jensen, a biotechnology analyst at Ernst & Young in Palo Alto, California. “Whether it will work out, or give us the first bad news about RNA interference, we don't know yet.”

Light relief: RNAi may stop the degeneration seen here (right) in an ageing retina. Credit: P. PARKER/SPL

Acuity hopes to use a small interfering RNA to treat patients with wet age-related macular degeneration. The condition is caused by extended growth of blood vessels in the retina — a problem that Acuity thinks can be tackled by silencing the gene that triggers the growth. The company says that the condition affects more than 1.65 million people in the United States.

Dale Pfost, Acuity's chief executive, says his firm has applied for a patent on the RNA molecule involved, but the intellectual-properties issues are not straightforward. Rival firm Alnylam, based in Cambridge, Massachusetts, has already requested a patent on the method of RNA delivery that Acuity will use. Alnylam says it plans to begin its own clinical trials in macular degeneration next year.

Pfost is confident that Acuity's disease-specific patent will be granted, but Alnylam begs to differ. “We're very pleased to see silencing RNAs entering the clinical stage,” says John Maraganore, chief executive of Alnylam. “But at the end of the day, we believe that anybody developing RNAi therapies needs to talk to us.”