A majority of health advisers said GlaxoSmithKline Plc's diabetes drug Avandia did not raise a concern about the risk of death when compared with other diabetes drugs.
Twenty members of the 33-member expert panel said available data did not raise concern about the death risk associated with Avandia when compared to diabetes drugs in other classes. It was not immediately clear how many could not decide.
By a closer 12-7 margin, the panel found no death concern with Avandia versus Takeda Pharmaceutical Co's Actos, a drug in the same class as Avandia. 14 could not decide.
A short time earlier on Wednesday, the scientific experts found Avandia raised a heart attack concern versus other classes of diabetes drugs and when compared Actos.
A final vote on whether to recommend Avandia's withdrawal from the market is expected shortly.
Avandia's U.S. sales were just 1.5 percent of Glaxo's 2009 revenues, but investors fear the company could face more lawsuits if the drug is pulled from the market.
The Food and Drug Administration convened the panel of outside experts to help the agency settle a three-year safety dispute over Avandia.
It is difficult to predict how early votes may affect the final vote.
In 2007, an advisory panel voted 20-3 that Avandia may increase the chances of a heart attack for some patients, but by 22-1 recommended that the drug stay on the market.
We believe it's likely that the drug will remain on the market but with increased warnings, said Morningstar analyst Damien Conover.
Starting Tuesday, the scientific experts heard two days of sharply conflicting opinions and reviewed hundreds of pages of data on whether Avandia causes heart attacks.
Glaxo shares were trading down 0.2 percent in New York, having closed up 0.4 percent in London.
The advisory panel is next due to vote on recommendations ranging from keeping the drug on the market with no warnings, to urging a withdrawal. Restrictions on use or beefing up warnings are among other choices.
Because the FDA asked panelists to select only one of the five options, there may be no clear majority. However, any vote short of withdrawal would back continued Avandia sales in some form.
The agency will make the final call in the coming months but usually follows the advice of its panels.
The debate on Avandia's safety has raged since warnings were placed on the drug in 2007 saying some research linked the drug to a higher heart attack risk but the data is inconclusive.
(Reporting by Lisa Richwine and Susan Heavey; Additional reporting by Lewis Krauskopf in New York; Editing by Tim Dobbyn)