A drug discovered more than 100 years ago may hold the key to combating autism symptoms, according to a study.

Researcher Dr Robert Naviaux of the San Diego School of Medicine gave suramin, a drug first developed in 1916, to 10 autistic boys between the ages of five and 14, and noted transformative results.

"After the single dose, it was almost like a roadblock had been released," he said. "If the future studies show that there's continued health benefits, this could be a game-changer for families with autism."

The study, which has been published in the Annals of Clinical and Translational Neurology, saw five of the participants receive suramin, while the remainder were given placebos. Included in the group were four non-verbal children – two six year olds and two 14 year olds.

"The six year old and the 14 year old who received suramin said the first sentences of their lives about one week after the single suramin infusion," Naviaux told the UC San Diego Health website. "This did not happen in any of the children given the placebo."