UPDATE 1-Merck halts study of "ineffective" HIV vaccine

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By Ransdell Pierson

NEW YORK, Sept 21 (Reuters) - Merck & Co (MRK.N: Quote, Profile, Research, Stock Buzz) has halted testing of its vaccine to prevent infection with HIV -- long considered among 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.

The 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.

Study investigators have been instructed to discontinue vaccinating volunteers and to monitor them, Merck said.

The study was aiming to determine whether the vaccine prevented HIV infection and whether it reduced the amount of virus in those who developed infection. Although a number of medicines have been introduced in recent years that control the virus and keep symptoms of the otherwise fatal disease at bay, doctors have said a preventive vaccine is by far the best way to control continued spread of the disease.