University of Kentucky researchers have found that RNA-interference-activating drugs now being tested in clinical trials do not work by silencing genes but by activating the immune system.

That could mean these drugs are not really precise tools and could have unexpected side effects.

The drugs aim to inactivate a gene contributing to leaky blood vessels in the back of the eye, the hallmark of the severe form of macular degeneration.

The researchers found that virtually any sequence of RNA, not just the ones in the drugs, worked. The RNA snippets were actually binding to an immune system sentry.

This raises the question of whether RNA drugs for other diseases could also set off similar immune responses and have other side effects.