The spate of bad news about painkillers has dealt a major setback to what had been a highly promising effort to use the drugs to prevent a host of leading killers, including many types of cancer, Alzheimer's and other forms of dementia.
Since concerns emerged that drugs such as Vioxx and Celebrex might cause heart attacks and strokes, researchers testing the drugs in dozens of studies have been frantically scouring whatever data they have gathered so far for signs of danger, urgently debating whether the trials should continue, and quickly informing participants of possible risks.
Several large studies have shut down fully or partially, including trials for preventing colon cancer, prostate cancer, Alzheimer's and, just last week, two large international studies evaluating Celebrex to cut the risk of getting breast cancer or suffering a recurrence. Other studies have been temporarily suspended until all participants could be warned of the possible danger.
Overall, the startling new concerns about the drugs' safety have cast a pall over what had been one of the most exciting fields of biomedical research, which was trying to harness important new insights into the underlying cause of a wide spectrum of illnesses.
"It's definitely been a big setback," said Raymond N. DuBois of Vanderbilt University School of Medicine in Nashville. "It's really disappointing because there had been a lot of enthusiasm in this area, and a lot of trials were underway. I think this is going to slow things down considerably. It's really unfortunate."
The developments are particularly distressing because a large body of evidence indicates the drugs could provide significant benefits aside from relieving pain. Even the studies that revealed the possible heart disease and stroke risks produced evidence that the approach could be highly effective for reducing the risk for cancer.
"We have produced evidence for the proof-of-principle that agents like these could be effective for preventing cancer," said Robert Bresalier of the University of Texas M.D. Anderson Cancer Center in Houston, who led the study that raised the first alarm. "There's a great deal of data suggesting that these drugs might be beneficial in terms of preventing or treating a large number of cancers. It would be a major mistake not to go forward with this line of research."
Several researchers said they believed the response to revelations of what are potential risks was an overreaction. It may turn out that Celebrex and similar drugs pose less of a danger than initially suspected, or that the drugs could prove useful at lower doses or for certain patients, they said.
"I think we have created a situation of mass hysteria that's completely unwarranted," said Carol Fabian, director of breast cancer prevention at the University of Kansas Medical Center in Kansas City, who decided to continue two breast cancer studies after warning participants of the possible risk. "I don't think we have all the data yet, and we may be prematurely drawing conclusions."
The drugs were developed to relieve pain with fewer side effects than existing painkillers, but researchers began testing them to treat or prevent a variety of diseases because of their ability to reduce inflammation, limit cell growth, inhibit the growth of blood vessels that nourish tumors and, in the case of breast cancer, lower estrogen levels.
A cascade of panic began in September when Merck & Co. pulled its blockbuster arthritis drug Vioxx from the market because Bresalier's study indicated the drug doubled the risk for heart attacks and strokes. Bresalier was testing whether Vioxx reduced the risk for colon polyps, which can lead to cancer. Merck then shut down another colorectal cancer-prevention trial, as well as one for prostate cancer prevention.
That prompted the National Institutes of Health to begin scrutinizing other trials using similar drugs, especially Pfizer Inc.'s popular Celebrex. On Dec. 17, the NIH announced that another cancer prevention trial had found evidence of a similarly increased risk for heart problems for Celebrex, and shut down that trial.
Although another study contradicted that finding, the announcement caused patients in many studies testing Celebrex to stop taking their drugs, including those in a large Alzheimer's prevention trial. That trial also raised concern about the over-the-counter pain reliever naproxen, sold as Aleve.
John Breitner of the University of Washington in Seattle, who led the Alzheimer's trial, said the hint of risk for naproxen was far from clear from his data, and the main reason his trial shut down was because so many participants were worried about Celebrex.