Clinical pharmacology of novel selective COX-2 inhibitors

Novel coxibs (i.e. etoricoxib, valdecoxib, parecoxib and lumiracoxib) with enhanced biochemical cyclooxygenase (COX)-2 selectivity over that of rofecoxib and celecoxib have been recently developed. They have the potential advantage to spare COX-1 activity, thus reducing gastrointestinal toxicity, even when administered at high doses to improve efficacy. They are characterized by different pharmacodynamic and pharmacokinetics features. The higher biochemical selectivity of valdecoxib than celecoxib, evidenced in vitro, may be clinically relevant leading to an improved gastrointestinal safety. Interestingly, parecoxib, a pro-drug of valdecoxib, is the only injectable coxib. Etoricoxib shows only a slightly improved COX-2 selectivity than rofecoxib, a highly selective COX-2 inhibitor that has been reported to halve the incidence of serious gastrointestinal toxicity compared to nonselective nonsteroidal antiinflammatory drugs (NSAIDs). Lumiracoxib, the most selective COX-2 inhibitor in vitro, is the only acidic coxib. The hypothesis that this chemical property may lead to an increased and persistent drug accumulation in inflammatory sites and consequently to an improved clinical efficacy, however, remains to be verified. Several randomized clinical studies suggest that the novel coxibs have comparable efficacy to nonselective NSAIDs in the treatment of osteoarthritis, rheumatoid arthritis and acute pain, but they share similar renal side-effects. The apparent dose-dependence of renal toxicity may limit the use of higher doses of the novel coxibs for improved efficacy. Large-size randomized clinical trials are ongoing to define the gastrointestinal and cardiovascular safety of the novel coxibs.     

Gastroduodenal safety of cyclooxygenase-2 inhibitors

Cyclooxygenase-1 (COX-1) derived eicosanoids promote gastroprotective mucosal defenses and induce platelet aggregation. By sparing COX-1, COX-2 specific inhibitors provide effective anti-inflammatory and analgesic activity while substantially reducing the risk of peptic ulcer disease and GI bleeding compared to dual COX inhibitors (traditional NSAIDs). Clinical studies of the COX-2-selective inhibitors have demonstrated efficacy equivalent to nonselective NSAIDs with significantly lower rates of GI toxicity. The incidence of endoscopic ulcers in some studies with coxibs has approximated placebo. However, as the detection of endoscopic lesions is not always correlated with symptomatic ulcers and ulcer complications, outcome studies of GI safety were performed. The results of large outcome studies have evaluated rofecoxib and celecoxib in over 39,000 patients with osteoarthritis or rheumatoid arthritis. Results of these studies showed that patients taking a supratherapeutic dose of rofecoxib or celecoxib had significantly lower rates of GI-related adverse events than those taking a nonselective NSAID. The GI safety of coxibs for patients using low dose aspirin concomitantly with a coxib appears to be reduced, particularly with regard to ulcer complications. Such data provide support for the COX-2 hypothesis and demonstrate that coxibs provide effective treatment of pain and inflammation with a reduced risk of gastropathy.     

COX-2 inhibitors and arterial hypertension: an analysis of spontaneous case reports in the Pharmacovigilance database

Objective To evaluate the main characteristics of case reports of arterial hypertension (AH) related to COX-2 inhibitor (coxib) use in real-life practice.Methods This study was based on spontaneous reports of adverse drug reactions (ADRs) submitted to the French Pharmacovigilance system. Associations between AH and the different groups of those using non-steroidal anti-inflammatory drugs (NSAIDs: rofecoxib, celecoxib and non-selective NSAIDs) were compared using calculation of the odds ratio (OR) with 95% confidence intervals (CIs).Results In France, between 1 April 2000 and 30 November 2003, 34 AH cases related to coxibs were reported. Case reports include predominantly patients older than 65 years, with a previous story of essential AH. Most AH (60%) occurred during the first 15 days of treatment. The AH was reported significantly more frequently for rofecoxib than celecoxib. The OR for development of AH with rofecoxib versus celecoxib was 3.3 (1.6–6.9). The AH was also reported more frequently with coxib (2.8%) than with non-selective NSAID (0.5%) use, OR = 5.9 (3.8–9.0).Conclusion This study shows that coxibs are associated with a risk of AH in real-life practice. More spontaneous reports of AH to the French Pharmacovigilance system concern rofecoxib than celecoxib (and coxibs than non-selective NSAIDs). This ADR is of special epidemiological importance due to both the risks of AH and the large use of coxibs.     

COX-2 selective inhibitors in the treatment of arthritis: a rheumatologist perspective

COX-2 selective inhibitors were developed in order to provide similar efficacy to traditional nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) but with improved upper gastrointestinal safety. This paper presents an overview of randomized clinical trials demonstrating the efficacy of COX-2 selective inhibitors for the treatment of patients with arthritis, particularly osteoarthritis and rheumatoid arthritis. In osteoarthritis and rheumatoid arthritis, COX-2 selective inhibitors have been shown to be more effective than placebo and similarly effective as standard doses of nonselective NSAIDs. There are currently few randomized clinical trials comparing the efficacy of the 2 first-generation COX-2 selective inhibitors, celecoxib and rofecoxib, in osteoarthritis. Of 4 head-to-head studies comparing the 2 agents, 3 indicated similar efficacy, while the other demonstrated superiority of rofecoxib at a dose of 25 mg qd compared with celecoxib at a dose of 200 mg qd. There are no clinical trials comparing the efficacy of different agents for treatment of patients with rheumatoid arthritis. Some studies have also demonstrated efficacy for COX-2 selective inhibitors in patients with ankylosing spondylitis and gout. In aggregate, these data show that COX-2 selective inhibitors provide effective relief of pain in patients with osteoarthritis and rheumatoid arthritis, with efficacy that is similar to traditional NSAIDs. Cost-effectiveness and cost-utility studies suggest, however, that their use should be limited to patients at high risk of serious upper gastrointestinal side effects, including complicated ulcers.     

Taking stock of coxibs

Highly selective COX-2 inhibitors ('coxibs') were developed in an attempt to minimise severe gastrointestinal toxicity associated with conventional NSAIDs, without loss of anti-inflammatory efficacy. Five years ago, we concluded that the evidence then available indicated, at most, a small advantage for rofecoxib and celecoxib (the first coxibs to be marketed) over conventional NSAIDs in terms of reduced risk of severe gastrointestinal complications, such as bleeding or perforation of gastric or duodenal ulcers. In September 2004, newly released evidence about cardiovascular risk with rofecoxib led Merck Sharp & Dohme to voluntarily withdraw the drug worldwide. This has raised questions about the balance of benefit and risk with coxibs in general. Here we discuss the evidence relating to the gastrointestinal and cardiovascular safety of coxibs in patients with osteoarthritis (OA) or rheumatoid arthritis (RA).     

Dual carbonic anhydrase--cyclooxygenase-2 inhibitors

Cyclooxygenase is a key enzyme responsible for metabolisation of arachidonic acid into prostaglandins and thromboxane. This enzyme is the target of non steroidal anti-inflammatory drugs (NSAIDs), used against inflammation and pain. The inducible COX-2 was associated with inflammatory conditions, whereas the constitutive form (COX-1) was responsible for the beneficial effects of the PGs. This observation led to the development of COX-2 inhibitors or "coxibs" of which rofecoxib (Vioxx) characterized by a methylsulfone moiety and the sulfonamides celecoxib (Celebrex) and valdecoxib (Bextra). Initially described as COX-2 "selective" inhibitors, recent reports revealed a nanomolar inhibition activity of the sulfonamide COX-2 inhibitors for several carbonic anhydrase (CA) isoforms, confirmed by X-ray crystal structures for the adducts of celecoxib and valdecoxib with isozyme CA II. This dual activity may help to explain differences in clinical observation between sulfonamide and methylsulfone COX-2 inhibitors. Moreover, the inhibition of CA isozymes, critical for the development and invasion of cancer cells, such as CA II, IX and XII, may constitute an important mechanism of antitumor action of such sulfonamide compounds.     

Risk-benefit perspectives in COX-2 blockade

The withdrawal of the celebrity arthritis drug, rofecoxib (Vioxx) has sparked an intense discussion and controversy about the safety of the selective COX-2 inhibitors. Laboratory, epidemiological, and clinical studies have surged and continued to evaluate and understand the safety of coxibs and traditional NSAIDs. This paper reviews the scientific and clinical basis of not only the risks, but also the benefits surrounding the use COX-2 inhibitors and NSAIDs. Discussion, debate, opinions, regulatory and clinical recommendations have evolved since the unexpected emergence of cardiac thrombotic events from the use of these drugs. The evidence by which coxibs and NSAIDs can potentially attenuate or exacerbate cardiovascular disease by affecting endothelial function is assessed; and how NSAIDs and coxibs affect renal function and blood pressure is revisited. Several investigations provide insight into their mechanism and clinical application.     

Defects in mouse nephrogenesis induced by selective and non-selective cyclooxygenase-2 inhibitors

BACKGROUND AND PURPOSE

Deletion of the cyclooxygenase-2 (COX-2) gene causes impairment of kidney development, but the effect of selective inhibitors of COX-2 (coxibs) or the non-selective inhibitors of COX (the classical non-steroidal anti-inflammatory drugs; NSAIDs) on kidney development was less well described.

EXPERIMENTAL APPROACH

We assessed the effects of equipotent analgesic doses of celecoxib, rofecoxib, valdecoxib, etoricoxib and lumiracoxib and of the NSAIDs, diclofenac and naproxen, on postpartum kidney development in mice, from postnatal day 1 (P1) to P21.

KEY RESULTS

All the COX inhibitors, at the doses used, blocked COX-2 activity by more than 80% as assayed by PGE₂ synthesis in lipopolysaccharide-stimulated mouse blood samples. Rofecoxib, etoricoxib and lumiracoxib exerted the most marked impairment of postpartum kidney development, demonstrated by attenuation of kidney growth, reduction in size of glomeruli, increase in immature superficial glomeruli, thinning of subcapsular cortical mass and reduction in size of juxtamedullary glomeruli. These defects were less severe than those in kidneys from COX-2^−/− mice. Administration of diclofenac and naproxen revealed renal defects similar to those after coxib treatment, but both NSAIDs induced greater arrest of immature superficial glomeruli in the outer cortex and increased the number of undifferentiated proliferating cell nuclear antigen-positive cells. Treatment with celecoxib or valdecoxib caused only minimal changes in renal morphology.

CONCLUSIONS AND IMPLICATIONS

Classical NSAIDs cause similar or even stronger nephrodysgenesis than the coxibs. Also, the ranking of coxibs regarding adverse effects on renal development, using equi-analgesic doses, is rofecoxib = etoricoxib = lumiracoxib > valdecoxib > celecoxib.     

Cyclooxygenase inhibitory natural products: current status

Non-steroidal anti-inflammatory drugs (NSAIDs) are of huge therapeutic benefit in the treatment of rheumatoid arthritis and various types of inflammatory conditions. The target for these drugs is cyclooxygenase (COX), a rate-limiting enzyme involved in the conversion of arachidonic acid into inflammatory prostaglandins. COX-2 selective inhibitors are believed to have the same anti-inflammatory, anti-pyretic and analgesic activities as that of nonselective inhibitor NSAIDs with little or none of the gastrointestinal side effects. Thus, in the last 6-7 years several selective COX-2 inhibitors including coxibs were discovered and introduced into clinic. Recent reports evidence that selective COX-2 inhibitor such as rofecoxib, can lead to thrombotic cardiovascular events through inhibition of prostacyclin formation in the infracted heart. This has resulted in withdrawal of rofecoxib from the clinic in September 2004. Moreover, the COX-2/COX-1 selectivity ratio is vital in the design of COX-2 inhibitory drugs, as it is clear from rofecoxib, which is more than 50-fold COX-2 selective. After looking at all above mentioned facts, natural product-based compounds seem better as these compounds are generally supposed to be devoid of severe side effects. The literature indicates that natural product-based compounds are mainly COX-1 selective. Through minor semi-synthetic changes in the structures, their selectivity towards COX-2 can be increased. The present review article addresses natural product COX inhibitors of plant and marine origin, reported during last ten years and their advantages, possible leads for further development and current status. In addition we describe our experience in the characterization, design and synthesis of potential natural COX inhibitors.     

Assessment of the safety of selective cyclo-oxygenase-2 inhibitors: where are we in 2003?

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used drugs worldwide despite their well-documented adverse gastrointestinal (GI) effects. The risk of developing a severe GI event varies from patient to patient and NSAID to NSAID. Selective cyclo-oxygenase-2 inhibitors (coxibs) have been designed to have similar efficacy but less GI toxicity than traditional NSAIDs, and have been shown to have an improved GI tolerability and less adverse events across a range of different GI safety assessments. In clinical trials, particularly VIGOR and CLASS, rofecoxib and celecoxib, respectively, significantly reduce the risk of ulcers and ulcer complications than nonselective NSAID comparators with ulcer rates comparable to placebo. The real benefit of a coxib comes from the sparing of the thromboxane and hence preservation of normal platelet function. Thus, there is less risk of bleeding with selective inhibition of COX-2, which is the most common and serious complication of non-selective NSAIDs. Moreover, bleeding can occur anywhere in the GI tract. Although some concern has been raised about the cardiovascular safety of coxibs, when used in recommended doses, there is no convincing evidence that patients treated with a coxib have an increased risk of cardiovascular thrombotic events. Different approaches have been advocated to minimize NSAID-related GI toxicity. Choice of less harmful NSAIDs such as coxib has been one of the strategies promoted in guidelines. The introduction of coxibs with a higher benefit-risk ratio has dramatically changed the therapeutic scenario for anti-inflammatory treatment in the clinical practice.     

Assessment of the safety of selective cyclo-oxygenase-2 inhibitors: where are we in 2003?

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most widely used drugs worldwide despite their well-documented adverse gastrointestinal (GI) effects. The risk of developing a severe GI event varies from patient to patient and NSAID to NSAID. Selective cyclo-oxygenase-2 inhibitors (coxibs) have been designed to have similar efficacy but less GI toxicity than traditional NSAIDs, and have been shown to have an improved GI tolerability and less adverse events across a range of different GI safety assessments. In clinical trials, particularly VIGOR and CLASS, rofecoxib and celecoxib, respectively, significantly reduce the risk of ulcers and ulcer complications than nonselective NSAID comparators with ulcer rates comparable to placebo. The real benefit of a coxib comes from the sparing of the thromboxane and hence preservation of normal platelet function. Thus, there is less risk of bleeding with selective inhibition of COX-2, which is the most common and serious complication of non-selective NSAIDs. Moreover, bleeding can occur anywhere in the GI tract. Although some concern has been raised about the cardiovascular safety of coxibs, when used in recommended doses, there is no convincing evidence that patients treated with a coxib have an increased risk of cardiovascular thrombotic events. Different approaches have been advocated to minimize NSAID-related GI toxicity. Choice of less harmful NSAIDs such as coxib has been one of the strategies promoted in guidelines. The introduction of coxibs with a higher benefit-risk ratio has dramatically changed the therapeutic scenario for anti-inflammatory treatment in the clinical practice.     

Cyclooxygenase-2 inhibitors and coronary occlusion--exploring dose-response relationships

AIMS: To investigate the relationship between acute coronary syndrome (ACS) and ingested doses of selective cyclooxygenase-2 (COX-2) inhibitors and other nonsteroidal anti-inflammatory drugs (NSAIDs). METHODS: Case-control study, commenced August 2003. Cases were patients admitted to hospital with ACS (myocardial infarction/unstable angina). Controls were hospital patients admitted for reasons other than acute vascular ischaemia or conditions that are believed to be complications of treatment with COX-2 inhibitors or NSAIDs. Structured interviews were undertaken within 7 days of admission, collecting information on cardiovascular events and risk factors and all ingested drugs, including the doses of COX-2 inhibitors and NSAID consumed in the previous week and month. RESULTS: An interim analysis of the data was conducted in late 2004 to inform a review of the COX-2 inhibitors by the Australian drug regulatory agency. Between August 2003 and October 2004, we recruited 328 ACS cases and 478 controls. With non-use of COX-2 inhibitors or NSAIDs as the reference the adjusted odds ratios (OR) for ACS were: celecoxib 1.11 (95% confidence interval 0.59, 2.11), rofecoxib 0.63 (0.31, 1.28) and other NSAIDs 0.67 (0.41, 1.09). Among control subjects, median daily ingested doses of celecoxib and rofecoxib were 200 mg and 13.4 mg, respectively. Using these to stratify risk, adjusted ORs for ACS were: 'low' dose (< median) 0.44 (0.19, 1.03); 'high' dose (>/= median) 1.22 (0.67, 2.21). A test for interaction across doses was statistically significant, OR 2.8 (1.0, 7.7), suggesting that at low doses, COX-2 inhibitors may be protective, becoming risk-inducing only at higher doses. CONCLUSION: The possibility that the gradient of cardiovascular risk with COX-2 inhibitors runs from protective to risk-inducing has biological plausibility and merits further investigation.     

Adverse drug reactions to nonsteroidal anti-inflammatory drugs, COX-2 inhibitors and paracetamol in a paediatric hospital

AIMS: The use of nonsteroidal anti-inflammatory drugs (NSAIDs) in children has rapidly escalated over the last 5 years in Australia. This is primarily as a result of the availability of ibuprofen as an over-the-counter preparation. Several recent, significant adverse drug reactions (ADRs) to NSAIDs, at the Royal Children's Hospital (RCH) in Melbourne, Australia prompted review of all of the RCH reactions reported to these agents over 5 years. METHODS: The ADR programme documents both spontaneously reported ADRs and ADRs identified by discharge coding. For this study, reported reactions to aspirin, celecoxib, ibuprofen, indomethacin, naproxen, paracetamol and rofecoxib, for the previous 5-year period, were retrieved from the hospital ADR database. RESULTS: Nineteen reports of ADRs to NSAIDs and six to paracetamol, in patients aged from 4 months to 22 years (median 10 years) were identified. Reactions were predominantly rash (n = 10), gastrointestinal (n = 5) and respiratory (n = 4) side-effects. These included reports of haematemesis with both celecoxib and ibuprofen. One patient died of severe acute exacerbation of asthma following initiation of rofecoxib. CONCLUSION: NSAID exposures are a significant cause of morbidity in children. Both nonselective NSAIDs and the newer COX-2 inhibitors were associated with significant drug reactions. The overall severity of these ADRs highlights the need for vigilant surveillance of ADRs in paediatrics, including both established and newer agents.     

Clinical pharmacology of celecoxib, a COX-2 selective inhibitor

NSAIDs are extensively used worldwide; nonetheless, they are associated with adverse gastrointestinal (GI) effects. COX-2 inhibitors (coxibs) have been developed to reduce pain and inflammation without associated GI and bleeding risks. Celecoxib was the first COX-2 inhibitor introduced on the market, and it still remains so, whereas rofecoxib and valdecoxib were withdrawn due to excess cardiovascular (CV) risk. There is consequently a concern that CV toxicity reflects a class effect of all COX-2 inhibitors. Celecoxib possesses anti-inflammatory and analgesic properties, and the evidence for CV risk is rather small and comparable to that of other traditional NSAIDs in short-term treatments (of < 4 weeks). It could be suggested that the use of low doses of celecoxib (100 mg b.i.d.) in short-treatment, especially in patients with previous experience of GI events and the recommendation of avoiding use of celecoxib in patients with CV history or risk, contribute in the decision-making process of prescribing COX-2 or NSAIDs.     

A clinical audit of the prescribing of celecoxib and rofecoxib in Australian rural general practice

AIMS: The new cyclooxygenase-2 (COX-2) selective inhibitors, celecoxib (Celebrex) and rofecoxib (Vioxx), have been widely prescribed since their launch. No reviews currently appear in the literature of prescribing patterns in Australia. This paper describes a self-audit of the clinical use of selective COX-2 inhibitor therapy undertaken with rural general practitioners (GPs) in Australia. METHODS: A structured audit form was developed and distributed to interested GPs. The form was self-administered and focused on issues about COX-2 inhibitors and the types of patients who were receiving them, e.g. indications, patient demographics, risk factors and drug interactions. RESULTS: A total of 627 patients were recruited (569 celecoxib and 58 rofecoxib). A range of doses was prescribed. Osteoarthritis was the most common indication (68.1%). Risk factors known for the nonselective nonsteroidal anti-inflammatory drugs were identified in 65.1% of patients, with the most common being advanced age, hypertension and previous peptic ulcer disease. Potential drug interactions were common. A variety of reasons for initiation of therapy was identified; these included perceived increased efficacy, safety and failure of other treatment. CONCLUSIONS: These results show that COX-2 inhibitors are being prescribed for patients with multiple risk factors that may place the patient at increased risk of adverse drug reactions to a COX-2 inhibitor. The perception of improved safety and efficacy was common and is of concern. Limitations of the study include the reliance on self-reporting.     

Comparison of reporting of Stevens-Johnson syndrome and toxic epidermal necrolysis in association with selective COX-2 inhibitors.

BACKGROUND: Stevens-Johnson syndrome and toxic epidermal necrolysis are closely related severe acute life-threatening, drug-induced skin disorders. The US FDA Adverse Events Reporting System (AERS) has received reports of Stevens-Johnson syndrome and toxic epidermal necrolysis associated with the use of the recently introduced selective cyclo-oxygenase (COX)-2 inhibitor NSAIDs, two of which are also sulfonamides. OBJECTIVE: The objective of this study is to review cases of Stevens-Johnson syndrome and toxic epidermal necrolysis reported to the FDA associated with the use of the selective COX-2 inhibitor NSAIDs celecoxib, rofecoxib and valdecoxib, and to compare reporting rates of the two conditions associated with these drugs to each other, meloxicam (an oxicam NSAID that came on the US market at a similar time) and the background incidence rate. METHODS: We reviewed all US cases of Stevens-Johnson syndrome and toxic epidermal necrolysis reported to the FDA AERS database associated with the use of celecoxib, rofecoxib, valdecoxib and meloxicam since these agents were first marketed. We utilised AERS and drug use data to calculate reporting rates for each drug after the first 2 years of marketing. We obtained the background rate from the medical literature. RESULTS: Up to the end of March 2004, there were 63 cases of Stevens-Johnson syndrome/toxic epidermal necrolysis reported with valdecoxib use, 43 with celecoxib, 17 with rofecoxib (the non-sulfonamide coxib) and none for meloxicam. In the first 2 years of marketing the reporting rate for Stevens-Johnson syndrome/toxic epidermal necrolysis with valdecoxib was 49 cases per million person-years of use, 6 cases per million person-years for celecoxib and 3 cases per million person-years for rofecoxib. The reporting rates for the sulfonamide coxibs were substantially higher than the background rate of 1.9 cases per million population per year, with the valdecoxib rate being 8-9 times that of celecoxib and approximately 25 times that of the background rate. CONCLUSION: There is a strong association between Stevens-Johnson syndrome/toxic epidermal necrolysis and the use of the sulfonamide COX-2 inhibitors, particularly valdecoxib. Physicians should be aware of the possibility of this serious life-threatening event when prescribing these drugs and advise patients to discontinue use at the earliest possible sign or symptom.     

Unexpected nanomolar inhibition of carbonic anhydrase by COX-2-selective celecoxib: new pharmacological opportunities due to related binding site recognition

By optimizing binding to a selected target protein, modern drug research strives to develop safe and efficacious agents for the treatment of disease. Selective drug action is intended to minimize undesirable side effects from scatter pharmacology. Celecoxib (Celebrex), valdecoxib (Bextra), and rofecoxib (Vioxx) are nonsteroidal antiinflammatory drugs (NSAIDs) due to selective inhibition of inducible cyclooxygenase COX-2 while sparing inhibition of constitutive COX-1. While rofecoxib contains a methyl sulfone constituent, celecoxib and valdecoxib possess an unsubstituted arylsulfonamide moiety. The latter group is common to many carbonic anhydrase (CA) inhibitors. Using enzyme kinetics and X-ray crystallography, we demonstrate an unexpected nanomolar affinity of the COX-2 specific arylsulfonamide-type celecoxib and valdecoxib for isoenzymes of the totally unrelated carbonic anhydrase (CA) family, such as CA I, II, IV, and IX, whereas the rofecoxib methyl sulfone-type has no effect. When administered orally to glaucomatous rabbits, celecoxib and valdecoxib lowered intraocular pressure, suggesting that these agents may have utility in the treatment of this disorder. The crystal structure of celecoxib in complex with CA II reveals part of this inhibition to be mediated via binding of the sulfonamide group to the catalytic zinc of CA II. To investigate the structural basis for cross-reactivity of these compounds between COX-2 and CA II, we compared the molecular recognition properties of both protein binding pockets in terms of local physicochemical similarities among binding site-exposed amino acids accommodating different portions of the drug molecules. Our approach Cavbase, implemented into Relibase, detects similarities between the sites, suggesting some potential to predict unexpected cross-reactivity of drugs among functionally unrelated target proteins. The observed cross-reactivity with CAs may also contribute to differences in the pharmacological profiles, in particular with respect to glaucoma and anticancer therapy and may suggest new opportunities of these COX-2 selective NSAIDs.