Pfizer is gambling on a 20,000-patient study that it hopes will prove once and for all that its COX-2 inhibitor Celebrex (celecoxib) is effective and no more likely to cause cardiovascular side effects than the older non-steroidal anti-inflammatory drugs ibuprofen and naproxen.

The outcome of study, said to cost in the region of $100 million, could either return Celebrex to the forefront of the marketplace for painkilling anti-inflammatory drugs, or spell the end of the product.

Celebrex is the last remaining COX-2 inhibitor on the US market, after Merck & Co’s Vioxx (rofecoxib) and Pfizer’s Bextra (valdecoxib) were withdrawn from sale because of a link to an increased risk of heart attacks and strokes in patients taking them. But sales of Celebrex have been hit hard by the controversy surrounding the COX-2 inhibitor class as a whole: Pfizer’s franchise brought in third-quarter revenues of $734 million, a decline of more than 60% compared to the same period of 2004, when Vioxx was withdrawn.

The trial – dubbed PRECISION - will be led by cardiologist Steve Nissen. Dr Nissen and Eric Topol, chairman of the Department of Cardiovascular Medicine at the Clinic, were among the first to highlight the potential risks associated with Vioxx.

The four-year trial will be organized by the Cleveland Clinic and will start enrolling patients early next year, according to a New York Times report. The study will enroll patients with osteoarthritis, the most common form of arthritis, who have known coronary heart disease or who have multiple risk factors for heart disease. Some patients with rheumatoid arthritis also will be included.

“Prior trials of pain relievers have not focused on these high-risk patients,” Dr Nissen said in a statement.