Merck halts study of "ineffective" HIV vaccine

By Ransdell Pierson

NEW YORK (Reuters) - Merck & Co has halted testing of its experimental HIV vaccine, long considered one of the most promising vaccines in development, after a monitoring board found it was ineffective, the company said on Friday.

The failed tests represent a major setback in the global effort to stem infections with the virus that causes AIDS. Merck had expressed great optimism for the vaccine, which it has been testing for a decade.

The independent Data Safety Monitoring Board, after reviewing interim results of the study of the vaccine, recommended discontinuing vaccinations of volunteers as the trial was headed for failure, Merck said.

"No one really knows when and if we will ever have an effective HIV vaccine because the virus is such a great challenge," Mark Feinberg, vice president of medical affairs at Merck's vaccine unit, said in an interview.

The vaccine consisted of a common cold virus loaded with three proteins found in the HIV virus.

"The concept was that if someone getting the vaccine is later exposed to HIV, the immune system would recognize those HIV proteins and go after the virus," said Keith Gottesdiener, another senior Merck research executive.

Asked if Merck would attempt to develop other HIV vaccines in the wake of the failed trial, Gottesdiener said, "At this point, we can't give an answer; we're just starting to look at this data and all its implications."

The New Jersey-based company, which was developing the product in partnership with the federally funded HIV Vaccine Trials Network, said two other early-stage trials of the vaccine had also been discontinued.