ViroPharma yesterday made it pretty clear that maribavir’s failure in one of two ongoing pivotal trials means the drug is probably heading for the R&D dustbin, at least in treating cytomegalovirus (CMV), a setback that robs the company of its biggest growth driver.

Investors were clearly disappointed, sending the stock down 53% to $5.74, a three-year low. With few treatment options available to either treat or prevent CMV, an infection that attacks patients with weakened immune systems, maribavir faced few barriers to commercial success, had clinical success been achieved. The news means that this year all eyes will be on the progress, or otherwise, of ViroPharma’s two marketed drugs, the antibiotic Vancocin, which is fending off generic threats, and newly launched Cinryze, for the rare inflammatory disorder hereditary angioedema (HAE).