These compounds set a high barrier for the virus, he notes, and early tests suggest that resistance to them is rare.
Pharmasset, a pharmaceutical firm in Princeton, New Jersey
, has several such drugs in development. One called RG7128 is in phase 2 clinical trials and is being developed by Pharmasset together with the Swiss drug giant Roche, based in Basel.
"We used to live in a monochromatic world," says Chung. "Now we realize there are several roads to the same destination.