A worldwide Phase II trial of a Merck HIVvaccine was halted after an independent reviewer found the vaccine ineffective,the firm said.

The trial of about 3,000 HIV-negative volunteers was being co-sponsored by Merck and the HIVVaccine Trials Network (HVTN), the largest clinical trials program for developingand testing HIV vaccines which is part of the NIH.

Merck had been testing the drug for 10 years and, while thevaccine was not thought to have huge commercial potential, it was considered importantin the global effort against the virus that causes AIDS. The best way to control the spread of the disease is thought to be through a prophylatic vaccine.

Had it worked, V520, as the vaccine was known internally, wouldhave added to a string of R&D successes for Merck that also have included Gardasil,a vaccine against the virus that causes cervical cancer, and Januvia, a diabetespill. Cordaptive, an extended-release niacin + flush inhibitor, was recently filed with the FDA.

“We share in the disappointment of the research and HIVcommunities today,” said Peter Kim, PhD, president, Merck Research Laboratories, in a statement. “Sadly,developing an effective AIDS vaccine remains one of the most challenging tasksfacing modern medicine.”

According to Merck, the independent Data Safety Monitoring Board reviewed safety data and results of an interim efficacy analysis of the study,recommending discontinuation because the trial willnot meet its efficacy endpoints.