Upjohn Stops Drug Trials After Deaths : Pharmaceuticals: Freedox is considered crucial to the firm’s future. The higher mortality rate is unexplained.

Tests on humans of a drug considered crucial to Upjohn Co.’s future have been suspended because of unexplained deaths among some American patients, the company announced Wednesday.

Upjohn, based in Kalamazoo, Mich., said it suspended the clinical trials of the drug Freedox for treatment of head injuries on the recommendation of an independent safety board.

The trials, which were 98% under way, showed a higher rate of mortality among patients who took the drug compared to patients who received a placebo.

The number of people who died wasn’t revealed, because doing so would skew the ongoing study of patients who have already received the drug, said Betsy Adams, a Food and Drug Administration spokeswoman.

“Stopping these clinical trials was the cautious and appropriate safety measure,” she said. “But it’s much too soon to say whether anything is wrong here.”

Shares of Upjohn fell $1.375 to $30.125 on the New York Stock Exchange, and industry analysts said the development could hasten the long-expected takeover of the weakened drug maker.

Freedox is the most promising drug being developed by Upjohn, which has been hurt recently by the expiration of patents on its key drugs, forcing them to compete against cheaper generic brands. Those drugs include Xanax, an anti-anxiety drug; Halcion, a sleeping pill, and Ansaid, a painkiller.

“This drug was going to be the driver of Upjohn through the 1990s,” NatWest Securities analyst Jack Lamberton said. “The projection was already bleak and is going to get much bleaker.”

Freedox, whose generic name is tirilazad mesylate, is also intended to treat strokes and related bleeding in the brain, but the FDA has hesitated granting approval for such treatment, saying test results have been inconclusive.

The deaths in the tests for head injuries came from brain swelling and herniation typical in such patients, the company said.