Cyclooxygenase 2 selective inhibitors: panacea or flash in the pan?

Multi-target drugs to address multiple checkpoints in complex inflammatory pathologies: evolutionary cues for novel "first-in-class" anti-inflammatory drug candidates: a reviewer's perspective

Inflammation is a complex, metabolically expensive process involving multiple signaling pathways and regulatory mechanisms which have evolved over evolutionary timescale. Addressing multiple targets of inflammation holistically, in moderation, is probably a more evolutionarily viable strategy, as compared to current therapy which addresses drug targets in isolation. Polypharmacology, addressing multiple targets, is commonly used in complex ailments, suggesting the superior safety and efficacy profile of multi-target (MT) drugs. Phenotypic drug discovery, which generated successful MT and first-in-class drugs in the past, is now re-emerging. A multi-pronged approach, which modulates the evolutionarily conserved, robust and pervasive cellular mechanisms of tissue repair, with AMPK at the helm, regulating the complex metabolic/immune/redox pathways underlying inflammation, is perhaps a more viable strategy than addressing single targets in isolation. Molecules that modulate multiple molecular mechanisms of inflammation in moderation (modulating TH cells toward the anti-inflammatory phenotype, activating AMPK, stimulating Nrf2 and inhibiting NFκB) might serve as a model for a novel Darwinian "first-in-class" therapeutic category that holistically addresses immune, redox and metabolic processes associated with inflammatory repair. Such a multimodal biological activity is supported by the fact that several non-calorific pleiotropic natural products with anti-inflammatory action have been incorporated into diet (chiefly guided by the adaptive development of olfacto-gustatory preferences over evolutionary timescales) rendering such molecules, endowed with evolutionarily privileged molecular scaffolds, naturally oriented toward multiple targets.

6b,11b-Dihydroxy-6b,11b-dihydro-7H-indeno[1,2-b]naphtho[2,1-d]furan-7-one (DHFO), a small molecule targeting NF-κB, demonstrates therapeutic potential in immunopathogenic chronic inflammatory conditions

6b,11b-Dihydroxy-6b,11b-dihydro-7H-indeno[1,2-b]naphtho[2,1-d]furan-7-one (DHFO), an easily synthesisable, orally bioavailable and relatively non-toxic small molecule synthesised in our lab, was previously reported to possess anti-oxidant, 5-lipoxygenase inhibitory, anti-inflammatory and peripheral analgesic activities. The present work deals with exploration of DHFO's efficacy in immunopathogenic chronic inflammatory conditions - arthritis and allergy. In carrageenan-induced inflammatory air pouch, which resembles the arthritic synovium, DHFO effectively reduced inflammatory redness and swelling and neutrophil infiltration. In complete Freund's adjuvant-induced arthritis, DHFO significantly decreased paw oedema and nitrite levels with efficacy comparable to diclofenac. DHFO inhibited neutrophil activation (observed as decreased myeloperoxidase levels), in both the in vivo models of inflammation. Interestingly, DHFO did not ulcerate the gastrointestinal tract, while diclofenac was observed to be extremely ulcerogenic. In antigen-induced active and passive anaphylaxis (allergy) models, DHFO dose-dependently prevented mesenteric mast cell (MC) degranulation with efficacy comparable to ketotifen. DHFO also inhibited compound 48/80 (C48/80)-induced paw oedema and peritoneal MC degranulation. DHFO stabilised p815 murine MCs stimulated by C48/80 and calcium ionophore-A23187, indicating an action downstream of calcium mobilisation. DHFO's anti-allergic mechanism could be two-pronged involving (1) inhibition of IgE production and/or (2) MC stabilisation. DHFO inhibited lipopolysaccharide (LPS)-induced pro-inflammatory mediator release (ROS, NO, IL-6 levels) and COX2 expression in RAW264.7 murine macrophages. Protein expression studies confirmed DHFO's ability to reduce nuclear levels of NF-κB in LPS-stimulated macrophages. Thus, DHFO is a promising non-ulcerogenic synthetic small molecule lead for immunopathogenic chronic inflammatory conditions.

Comparison of Lornoxicam and Rofecoxib in Patients with Activated Osteoarthritis (COLOR Study)

BACKGROUND AND OBJECTIVE

Impaired mobility and pain mean a loss of quality of life for patients with rheumatic diseases. Therefore the initial aim of therapy is rapid and efficient analgesia in order to achieve the best possible result for these patients. Lornoxicam is a strong analgesic and anti-inflammatory NSAID with balanced cyclo-oxygenase (COX)-1/COX-2 inhibition and excellent tolerability. In the course of the development of selective COX-2 inhibitors, it was maintained that COX-2 inhibitors decrease the risk of injury to the upper gastrointestinal (GI) tract with a similar efficacy to that of classic NSAIDs. However, a clinical trial comparing both substances has never been performed. In the present study we investigated the treatment of patients with osteoarthritis with lornoxicam in comparison with treatment with the selective COX-2 inhibitor rofecoxib. This multicentre clinical investigation focused on efficacy and tolerability.

PATIENTS AND METHODS

A total of 2520 patients (most of them with osteoarthritis) were treated over 25 days on average. Before and after treatment patients documented their individual scores for pain on movement, at rest and during the night, and their individual duration of morning stiffness as well as the consequent grade of restriction. At the end of the study all individuals involved judged the efficacy and safety of the therapy.

RESULTS

All improvements in each efficacy parameter were clinically relevant in each treatment group and significantly superior (p < 0.001) in the lornoxicam group. Pain on movement (-45.3%), at rest (-42.0%) and at night (-42.5%) was reduced by rofecoxib, whereas improvements after treatment with lornoxicam exceeded those effects significantly (-55.8%, -55.8% and -59.9%, respectively). Shortening of the duration of morning stiffness was significantly (p < 0.001) more pronounced with lornoxicam (-66.6%) than with rofecoxib (-50.2%). Nearly three times as many patients discontinued rofecoxib treatment because of lack of efficacy compared with lornoxicam treatment (8.9% versus 3.4%). Physicians judged lornoxicam to be markedly superior to rofecoxib, since excellent efficacy was observed in 40.9% of all cases versus 20.1% with rofecoxib. Serious adverse events did not occur. Adverse events were reported in 5.4% of all lornoxicam patients compared with 12.0% of the rofecoxib recipients (p < 0.001). GI symptoms showed a slight trend of being less frequent following rofecoxib therapy.

CONCLUSIONS

The results of this study confirmed the efficacy and safety of both drugs. Lornoxicam and rofecoxib are effective in the treatment of patients with activated osteoarthritis; the analgesic and anti-inflammatory effects of lornoxicam are significantly superior to those of rofecoxib without inferiority in tolerability.

Rofecoxib and clinically significant upper and lower gastrointestinal events revisited based on documents from recent litigation

INTRODUCTION

On the basis of published data, it is widely believed and cited that rofecoxib use is associated with approximately a 50% reduction in significant gastrointestinal (GI) complications such as bleeding.

METHODS

Data made available as part of litigation, including the Vioxx Gastrointestinal Outcomes Research trial and an Alzheimer's study, allow a reassessment of the reported benefits of rofecoxib in terms of a significant reduction in complicated GI events and in lower GI bleeding.

RESULTS

During the review process of the Vioxx Gastrointestinal Outcomes Research study, it was suggested that rofecoxib might have little benefit, with regard to GI toxicity, for patients with rheumatoid arthritis not treated with corticosteroids. Reanalysis of the original Merck data set showed 9 complicated confirmed events in the rofecoxib group compared with 10 in the naproxen group among corticosteroid nonusers and 7 versus 27 among corticosteroid users so that the difference between rofecoxib and naproxen in the occurrence of confirmed complicated perforations, ulcers or bleeds seemed to be entirely because of the effects within corticosteroid users. The claim that serious lower GI events were 54% lower with the use of the selective cyclooxygenase-2 inhibitor rofecoxib was stated to be based on an assessment blinded to treatment allocation. In fact, the choice did not represent the original blinded analysis that showed a nonsignificant difference, but rather was based on an assessment after treatment allocation was disclosed.

CONCLUSION

Examination and reanalysis of unpublished data regarding rofecoxib has failed to confirm a safety advantage of rofecoxib over traditional nonsteroidal anti-inflammatory drugs in terms of complicated upper or lower GI events.

Lumiracoxib in the management of osteoarthritis and acute pain

Lumiracoxib is a highly selective COX-2 inhibitor with a novel chemical structure and a relatively short plasma half-life. It has been approved in > 40 countries for the symptomatic treatment of osteoarthritis and/or acute pain related to primary dysmenorrhoea and dental or orthopaedic surgery. In these conditions, lumiracoxib has proved to be as effective as standard doses of conventional NSAIDs and other COX-2 selective inhibitors (coxibs). According to the Therapeutic Arthritis Research Gastrointestinal Trial, which enrolled 18,325 patients with osteoarthritis, lumiracoxib 400 mg/day (four times its recommended dosage) was associated with a significant decrease in the risk of ulcer complications compared with naproxen 1000 mg/day and ibuprofen 2400 mg/day, at least in the population not taking low-dose aspirin. The atherothrombotic potential of NSAIDs, especially coxibs, has been much debated. In this respect, available data do not suggest that lumiracoxib may be associated with an increased hazard of cardiovascular events compared with non-selective NSAIDs. Finally, lumiracoxib may be an effective and safe drug provided both physicians and patients will comply with its approved indications and contraindications.

Gastroprotection by coxibs: what do the Celecoxib Long-Term Arthritis Safety Study and the Vioxx Gastrointestinal Outcomes Research Trial tell us?

Current evidence suggests that PPIs might be effective in maintaining patients in remission during continued NSAID use and that the combination of omeprazole plus diclofenac is as effective as treatment with celecoxib in preventing recurrent bleeding. Larger outcome studies comparing the combination of a PPI with other nonselective NSAIDs and a selective COX-2 inhibitor (and the combination of a selective COX-2 inhibitor with a PPI or misoprostol) are required to determine whether or not any regimen will further decrease or eliminate the risk of ulcer complications in high-risk individuals.

Do altering in ornithine decarboxylase activity and gene expression contribute to antiproliferative properties of COX inhibitors?

Two isoforms of cyclooxygenase (COX) participate in growth control; COX-1 is constitutively expressed in most cells, and COX-2 is an inducible enzyme in response to cellular stimuli. An induction of COX-2 found in neoplastic tissues results in increased cell growth, inhibition of apoptosis, activation of angiogenesis, and decreased immune responsiveness. Although both COX-1 and COX-2 inhibitors are suppressors of cell proliferation and appear to be chemopreventive agents for tumorigenesis, the molecular mechanisms mediating antiproliferative effect of COX inhibitors are still not well defined. This study contrasts and compares the effects of aspirin and celecoxib, inhibitors of COX-1 and COX-2, in rat hepatoma HTC-IR cells. The following were assessed: cell proliferation and apoptosis, ornithine decarboxylase (ODC) activity, and pattern expression of three immediate-early genes, c-myc, Egr-1, and c-fos. We have shown that the treatment of hepatocytes in vitro with the selective COX-2 inhibitor, celecoxib, was associated with induction of apoptosis and complete inhibition of cellular proliferation. Aspirin exhibited a small antiproliferative effect that was not associated with apoptosis. Treatment with celecoxib produced dose- and time-dependent decrease in ODC activity. In addition, at higher drug concentration the decrease in ODC activity was greater in proliferating than in resting cells. Much lesser inhibitory effect on ODC activity was observed in aspirin-treated cells. The two COX inhibitors did not change c-myc expression, significantly decreased the expression of Egr-1, and differentially altered expression of c-fos; aspirin did not change, but celecoxib dramatically decreased the levels of c-fos-mRNA. Our study revealed that celecoxib and aspirin share the ability to inhibit ODC activity and alter the pattern of immediate-early gene expression. It seems that some of the observed effects are likely to be related to COX-independent pathways. The precise mechanisms of action of COX inhibitors should be defined before using these drugs for cancer chemopreventive therapy.

Clinical potential of cyclo-oxygenase-2 inhibitors

On the basis of their reduced potential to cause injury to the gastroduodenal mucosa, cyclo-oxygenase (COX)-2-selective inhibitors were developed and marketed as a safer alternative to traditional nonsteroidal anti-inflammatory drugs (NSAIDs). This manuscript reviews the major steps leading to the introduction of COX-2-selective inhibitors into clinical practice, from the identification of the COX isoenzymes to their various roles in physiological and pathological processes. The available data show that COX-2 inhibitors have a favourable safety profile and are at least as effective as traditional NSAIDs for the treatment of pain and inflammatory conditions with a reduced incidence of gastrointestinal complications. Emerging evidence points to new and unanticipated effects from these agents. COX-2 inhibition appears to play an important role in the modulation of intestinal polyposis and colorectal carcinogenesis. Additionally, COX-2 expression may be associated with inflammatory responses leading to the occurrence of Alzheimer's disease and potentially, COX-2 inhibitors could be used to retard the progression of this condition. However, by decreasing prostacyclin production, COX-2 inhibitors may lead to increased prothrombotic activity and increase the risk of cardiovascular events. Until further large-scale prospective studies are performed, and the magnitude of these potential risks is quantified, COX-2 inhibitors should be used with caution in patients at risk for cardiovascular morbidity.

Rofecoxib: a review of its use in the management of osteoarthritis, acute pain and rheumatoid arthritis

Rofecoxib is a selective cyclo-oxygenase (COX)-2 inhibitor which has little or no effect on the COX-1 isoenzyme at doses up to 1000 mg/day. Rofecoxib has greater selectivity for COX-2 than celecoxib, meloxicam, diclofenac and indomethacin. In well-controlled clinical trials, rofecoxib 12.5 to 500 mg/day has been evaluated for its efficacy in the treatment of osteoarthritis, acute pain and rheumatoid arthritis [lower dosages (5 to 125 mg/day) were generally used in the chronic pain indications]. In the treatment of patients with osteoarthritis, rofecoxib was more effective in providing symptomatic relief than placebo, paracetamol (acetaminophen) and celecoxib and was similar in efficacy to ibuprofen, diclofenac, naproxen and nabumetone. Overall, both the physician's assessment of disease status and the patient's assessment of response to therapy tended to favour rofecoxib. In patients with postsurgical dental pain, pain after spinal fusion or orthopaedic surgery, or primary dysmenorrhoea, rofecoxib provided more rapid and more sustained pain relief and reduced requirements for supplemental morphine use after surgery than placebo. Rofecoxib was more efficacious than celecoxib in patients with acute dental pain and pain after spinal fusion surgery, although celecoxib may have been used at a subtherapeutic dose. In comparison with traditional nonsteroidal anti-inflammatory drugs (NSAIDs) ibuprofen, diclofenac and naproxen sodium, rofecoxib was similar in efficacy in the treatment of acute pain. Although naproxen sodium provided more rapid pain relief than rofecoxib in patients with primary dysmenorrhoea, the reverse was true after orthopaedic surgery: rofecoxib provided more rapid pain relief and less supplemental morphine was needed. Rofecoxib was as effective as naproxen in providing symptomatic relief for over 8700 patients with rheumatoid arthritis. Compared with traditional NSAID therapy, rofecoxib had a significantly lower incidence of endoscopically confirmed gastroduodenal ulceration and, in approximately 13,000 patients with osteoarthritis and rheumatoid arthritis, a lower incidence of gastrointestinal (GI) adverse events. Rofecoxib was generally well tolerated in all indications with an overall tolerability profile similar to traditional NSAIDs. The most common adverse events in rofecoxib recipients were nausea, dizziness and headache. In conclusion, rofecoxib is at least as effective as traditional NSAID therapy in providing pain relief for both chronic and acute pain conditions. Rofecoxib provides an alternative treatment option to traditional NSAID therapy in the management of symptomatic pain relief in patients with osteoarthritis. Initial data from patients with primary dysmenorrhoea and postoperative pain are promising and further trials may confirm its place in the treatment of these indications. Rofecoxib has also shown promising results in patients with rheumatoid arthritis and is likely to become a valuable addition to current drug therapy for this patient population. Importantly, rofecoxib is associated with a lower incidence of GI adverse events than traditional NSAIDs making it a primary treatment option in patients at risk of developing GI complications or patients with chronic conditions requiring long term treatment.

Upper gastroduodenal ulceration in arthritis patients treated with celecoxib

OBJECTIVE

To evaluate the comparative incidence of endoscopic gastroduodenal ulcers in patients with rheumatoid arthritis or osteoarthritis treated with celecoxib.

DESIGN

Quantitative systematic review of randomized controlled trials.

SUBJECTS

Patients (n = 4632) with rheumatoid arthritis or osteoarthritis reported in five trials.

MAIN OUTCOME MEASURES

Rate ratios, rate differences, and the number needed to harm were calculated for the incidence of endoscopically documented gastroduodenal ulcers.

RESULTS

Pooled rate ratios (RRs) relative to placebo for endoscopic ulcers at 12 weeks were 1.96 (95% CI 0.85 to 4.55) for celecoxib 100 mg twice daily and 2.35 (95% CI 1.02 to 5.38) for celecoxib 200 mg twice daily. There was no significant difference in gastroduodenal ulcers at 12 weeks between celecoxib 200 mg twice daily and celecoxib 100 mg twice daily; the corresponding pooled RR was 1.21 (95% CI 0.62 to 2.38). In contrast, celecoxib 200 mg twice daily was associated with a significantly lower rate of gastroduodenal ulcers than was naproxen 500 mg twice daily at 12 weeks (RR 0.24; 95% CI 0.17 to 0.33). On average, for every seven patients treated with naproxen, one more had an endoscopic ulcer than if they were treated with celecoxib. Celecoxib 200 mg twice daily also had a significantly lower risk of endoscopic ulcers than did either modified-release diclofenac 75 mg twice daily at 24 weeks (RR 0.24; 95% CI 0.11 to 0.52) or ibuprofen 800 mg three times daily at 12 weeks (RR 0.30; 95% CI 0.20 to 0.46).

CONCLUSIONS

Endoscopic studies have shown that celecoxib, at a wide range of doses, is associated with a lower incidence of gastroduodenal ulcers than are diclofenac, ibuprofen, or naproxen. The incidence rates of gastroduodenal ulcers associated with celecoxib were similar, although not equivalent, to placebo. Head-to-head comparisons suggest that, at the wide range of doses studied (100-800 mg/d), there are no dose-related increases in endoscopic gastroduodenal ulcers with celecoxib. The results of longer term comparative trials of celecoxib based on clinical outcomes are needed to determine celecoxib's ultimate risk-benefit profile.

The treatment of peptic ulcer disease

There is a continuation of the debate on the management of dyspepsia while the role of Helicobacter pylori in duodenal ulcer disease is being questioned with renewed vigor, specifically in the United States. The interaction of NSAIDs and H. pylori provided some interesting, if at times confusing, literature while the debate on the safety of long-term acid suppression remained unresolved. There were some interesting developments with regard to therapeutic agents during this period. A fourth proton pump inhibitor was introduced to the market while cisapride, a drug previously considered safe, was effectively withdrawn from the North American market because of safety concerns. More data on the COX-1-sparing agents became available, and their impressive gastrointestinal safety profile was confirmed. It was noted, however, that the incidence of dyspepsia, experienced by users of these drugs, may remain a problem.