ViroPharma plunges as three studies reveal negative pleconaril data

Three late-stage clinical trials of ViroPharma's antiviral drugpleconaril have failed to show it was significantly more effective than placebo in treating viral respiratory infection (the common cold) and in viral meningitis. Shares in the company plunged more than 65% to close at $23.25 on April 11.

In the VRI study, time to resolution of illness was reduced from 9.4 days to 7.7 days (p=0.07), a non-significant outcome. However, in patients not taking concomitant cold medication a greater treatment benefit was observed, with time to resolution of illness reduced from 9.0 days to 6.75 days (p=0.03). Overall though, "in all randomized patients, generally less pronounced treatment benefits were seen in this study," says ViroPharma.

A second study, involving adult patients with viral meningitis, also failed to meet its primary endpoint (time to complete resolution of headache) when all randomized patients were evaluated. However, says ViroPharma, significant effects were seen among adult patients with the most serious disease, who presented with severe headache and vomiting. In this group, time to resolution of headache was reduced by three days (seven days versus 10 days among placebo receivers) with the same result seen in time to return to work.