COX-2 Inhibitor - Research History

Research History

For more details on this topic, see Discovery and development of cyclooxygenase 2 inhibitors.

The mouse COX-2 gene was cloned by UCLA scientist Dr. Harvey Herschman. The enzyme was discovered in 1988 by Daniel Simmons, a Brigham Young University researcher formerly of Harvard University. Dr. Simmons immediately understood the importance of his discovery. The same day the enzyme was sequenced, he had his notebook notarized as proof of his discovery. Subsequently, Pfizer, the research firm with whom Simmons had contracted, allegedly broke contract and refused to give Simmons any royalties and profits from his discovery. As of September 2010, a lawsuit is in progress by Simmons against the drug developers.

In the course of the search for a specific inhibitor of the negative effects of prostaglandins which spared the positive effects, it was discovered that prostaglandins could indeed be separated into two general classes which could loosely be regarded as "good prostaglandins" and "bad prostaglandins", according to the structure of a particular enzyme involved in their biosynthesis, cyclooxygenase.

Prostaglandins whose synthesis involves the cyclooxygenase-I enzyme, or COX-1, are responsible for maintenance and protection of the gastrointestinal tract, while prostaglandins whose synthesis involves the cyclooxygenase-II enzyme, or COX-2, are responsible for inflammation and pain.

The existing non-steroidal anti-inflammatory drugs (NSAIDs) differ in their relative specificities for COX-2 and COX-1; while aspirin and ibuprofen are equipotent at inhibiting COX-2 and COX-1 enzymes, other NSAIDs appear to have partial COX-2 specificity, particularly meloxicam (Mobic). Studies of meloxicam 7.5 mg per day for 23 days find a level of gastric injury similar to that of a placebo, and for meloxicam 15 mg per day a level of injury lower than that of other NSAIDs; however, in clinical practice meloxicam can still cause some ulcer complications.

Many COX-2-specific inhibitors have been removed from the U.S. market. As of December 2011, only Celebrex (generic name is celecoxib) is still available for purchase.

Valdecoxib and rofecoxib are about 300 times more potent at inhibiting COX-2, than COX-1, suggesting the possibility of relief from pain and inflammation, without gastrointestinal irritation, and promising to be a boon for those who had experienced such adverse effects previously or had comorbidities that could lead to such complications. Celecoxib is approximately 30 times more potent at inhibiting COX-2 than COX-1, with etoricoxib being 106 times more potent. Also, Tribulus terrestris was shown to have strong inhibitory activity on COX-2.

Although individual reactions to particular NSAIDs vary, in general the efficacy of COX-2 inhibitors has proved similar to that of other NSAIDs, as expected since both classes of drug inhibit the desired target, the action of COX-2 prostaglandins. The drug's effectiveness is similar to that of traditional NSAIDs such as ibuprofen, diclofenac, or naproxen.