World of Pain for a Class of Drugs

Right now, the COX-2 inhibitor drug market is riddled with uncertainty and in desperate need of pain relief.

Merck's ( MRK) Vioxx is gone. Its presumed successor, Arcoxia, is sold in 47 countries but not in the U.S.; and Merck is talking to foreign regulators about the drug following the U.S. Vioxx withdrawal.

In late October, the Food and Drug Administration granted conditional approval for Arcoxia, but that approval includes more clinical testing to assess long-term safety and efficacy. Merck has declined to provide details on what it would have to do and how long it would take. Clearly, Arcoxia won't reach the U.S. market for at least several years, and many analysts have dropped any prediction of U.S. sales for many years in their economic models.

As for Pfizer ( PFE), it recently added several warnings to the Bextra label. (For a brief history of Bextra and Celebrex click here.)

Since 2002, a year after Bextra reached the U.S. market, the drug's label has carried a warning about Stevens-Johnson syndrome, a rare and sometimes fatal skin reaction. Recently, Pfizer, after discussions with the FDA, paid notice to this dangerous side-effect with a black box warning, the strictest alert required by the FDA.

Pfizer also added a warning to the label reflecting a recent study that showed the drug poses a higher risk of cardiovascular problems for patients undergoing heart bypass surgery. The risk was detected among patients who took Bextra and another Pfizer COX-2 drug that is not available in the U.S.

Some of the these problems cited by the FDA include heart attack, stroke, blood clots in the legs and blood clots in the lungs.

Another study of heart bypass patients taking only Bextra revealed a higher cardiovascular risk that wasn't considered statistically significant compared to patients taking a placebo. In addition, Pfizer says a third study of patients undergoing general surgery found no significant risk of cardiovascular problems among those receiving Bextra and the other COX-2 drug.

Bextra is not approved in the U.S for any postsurgical care. Pfizer recently said it will conduct additional studies "to confirm the long-term cardiovascular safety profile" of Bextra for arthritis patients.

That other COX-2 drug, called Dynastat, is given intravenously and is a cousin of Bextra. Last month, Pfizer said it would submit an application to the FDA by year-end, or about six months later than the company originally had predicted. Dynastat is sold in 45 countries.

Another player in the COX-2 arena -- Novartis ( NVS) -- has kept a low profile because its drug, Prexige, is still under review by the FDA. The drug has been approved in 21 countries.

Novartis submitted its application to the FDA in November 2002. But in September 2003, the FDA said Novartis had to provide additional test results. At the time, Novartis predicted it would take until 2005 for the drug to reach the U.S. market. More recently, but before Vioxx was pulled, Novartis predicted that Prexige would reach U.S. pharmacies in 2006.

Late last month, Novartis withdrew its request for Prexige's approval in all European Union countries, pending a review of all COX-2 drugs by the EU counterpart of the FDA. Prexige has been approved by the U.K.

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