Anti-inflammatory and analgesic effect of LD-RT and some novel thiadiazole derivatives through COX-2 inhibition

Generally, highly selective COX-2 inhibitors cause cardiovascular side effects. Celecoxib is the highly marketed coxib, so there is still a need for the synthesis of COX-2 inhibitors with less adverse effects. Moreover, low-dose radiotherapy (LD-RT) is clinically used for the treatment of inflammatory diseases. The present study aimed to investigate the analgesic and anti-inflammatory activity of a novel series of 1,3,4-thiadiazole derivatives alone or combined with LD-RT with a single dose of 0.5 Gy. Initially, in vitro COX-1/COX-2 inhibition assays were performed, identifying the sulfonamide-containing compounds 5 – 10 as the most potent candidates, with IC₅₀ values in the range of 0.32–0.37 µM and the highest selectivity indices. These compounds and celecoxib were subjected to in vivo examination after their safety was assessed through the acute toxicity test. Treatment with compounds 5 – 10 inhibited carrageenan-induced edema by nearly 47–56%, which was nearly equivalent to celecoxib. Compounds 7 and 8 and celecoxib showed an analgesic activity of 64.15%, 49.05%, and 84.90%, respectively, whereas compounds 5 , 6 , 9 , and 10 did not show any analgesic activity unless combined with LD-RT. Ulcerogenic activity, histological paw examination, and docking studies were performed. Compounds 5 – 10 were nearly similar to celecoxib, showing normal histological features with no ulcerogenic activity.     

Enlarging the NSAIDs family: ether, ester and acid derivatives of the 1,5-diarylpyrrole scaffold as novel anti-inflammatory and analgesic agents

The development of the coxib family has represented a stimulating approach in the treatment of inflammatory disorders, such as arthritis, and for the management of acute pains, in relation to the well-known traditional Non-Steroidal Anti-inflammatory Drugs (t-NSAIDs). Prompted by the pursuit for new cyclooxygenase-2 (COX-2) inhibitors, endowed with fine tuned selectivity and high potency, in the past years we have identified novel classes of ether, ester and acid molecules characterized by the 1,5-diarylpyrrole scaffold as potentially powerful anti-inflammatory molecules (12-66). All compounds proved to exert an in vitro inhibition profile as good as that shown by reference compounds. Compounds bearing a p-methylsulfonylphenyl substituent at C5 displayed the best issues. In particular, ester derivatives proved to perform the best in vitro profile in terms of selectivity and activity toward COX-2. The cell-based assay data showed that an increase of hindrance at the C3 side chain of compounds could translate to activity enhancement. The human whole blood (HWB) test let to highlight that submitted compounds displayed 5-10 fold higher selectivity for COX-2 vs COX-1 which should translate clinically to an acceptable gastrointestinal safety and mitigate the cardiovascular effects highlighted by highly selective COX-2 inhibitors. Finally, to assess in vivo anti-inflammatory and analgesic activity three different tests (rat paw pressure, rat paw oedema and abdominal constriction) were performed. Results showed good in vivo anti-inflammatory and analgesic activities. The issues gained with these classes of compounds represent, nowadays, a potent stimulus for a further enlargement of the NSAIDs family. In this review we describe the results obtained by our research group on this topic.     

Evaluation of anti-inflammatory,analgesic activities,and side effects of some pyrazole derivatives

Background and purpose

Non-steroidal anti-inflammatory drugs are associated with several side effects, such as gastrointestinal mucosal damage, renal toxicity, and cardiovascular side effects. Aiming to find a novel analgesic/anti-inflammatory drug with minimal side effects, the present study was designed to screen and evaluate some newly synthesized pyrazole derivatives.

Method

Anti-inflammatory activity using carrageenan-induced rat paw edema and cotton-pellet-induced granuloma, COX-1/COX-2 selectivity using thin layer chromatography, and analgesic using hot plate and tail flick tests as well as ulcerogenic and renal side effects of the ten compounds were assessed.

Results and discussion

The results of the carrageenan-induced rat paw edema showed that the carboxyphenylhydrazone derivative (N9) was more potent than the chlorophenyl counterpart (N8) with a relative activity compared to celecoxib of 1.08 and ?0.13, respectively, after 1 h. Even though this is true, N9 caused significant increase in the ulcer index, creatinine, and Blood Urea Nitrogen levels. The cotton granuloma test showed that the carboxyphenylhydrazone derivative (N7) was also more potent than its chlorophenyl counterpart (N6) with a relative activity compared to celecoxib of 1.13 and 0.86, respectively. Moreover, adding an acetyl not only increased the anti-inflammatory activity from a relative activity compared to celecoxib of 0.57–1.17 for the compounds X4 and N5, respectively, in the granuloma test, but also increased the selectivity toward COX-2 from 0.197 to 47.979.

Conclusion

As a conclusion, from the ten compounds analyzed, N5 and N7 showed promising results as anti-inflammatory/analgesic agents with low ulcerogenicity and nephrotoxicity and thus should be further analyzed to determine the ED50 and other side effects.

     

Synthesis of novel N-substitutedphenyl-6-oxo-3-phenylpyridazine derivatives as cyclooxygenase-2 inhibitors

Some novel non-ulcerogenic N-substitutedphenyl-6-oxo-3-phenylpyridazines as COX-2 inhibitors have been developed (Supplementary material Appendix 1 ). The novel aldehyde 3 was prepared by reacting 6-phenylpyridazin-3(2H)-one with 4-fluorobenzaldehyde. The aldehyde 3 was reacted with different hydrazines and thiazolidin-4-ones to obtain the novel N-substitutedphenyl-6-oxo-3-phenylpyridazine derivatives. These were assessed for their anti-inflammatory potential and gastric ulcerogenic effects. The molecular docking investigations were also undertaken. The spectroscopic data were coherent with the allocated structures of the compounds. The compounds 4a (IC₅₀ = 17.45 nm; p < .05), 4b (IC₅₀ = 17.40 nm; p < .05), 5a (IC₅₀ = 16.76 nm; p < .05), and 10 (IC₅₀ = 17.15 nm; p < .05) displayed better COX-2 inhibitory activity than celecoxib (IC₅₀ = 17.79 nm; p < .05). These findings were consistent with the molecular docking investigations of 4a , 4b , 5a , and 10 . The in vivo anti-inflammatory profile of 4a , 4b , 5a , and 10 was also superior to celecoxib and indomethacin. The compounds 4b , 5a , and 10 revealed no gastric ulcerogenic effects, wherein the compound 4a produced almost negligible gastric ulcerogenic effects than celecoxib and indomethacin. The compounds 4a , 4b , 5a , and 10 have been postulated as promising non-ulcerogenic COX-2 inhibitors.     

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.     

Design, synthesis and pharmacological evaluation of 4-[2-alkylthio-5（4）-（4- substitutedphenyl）imidazole-4（5）yl]benzenesulfonamides as selective COX-2 inhibitors

Aim： To design and synthesize a series of benzenesulfonamide derivatives, 4-[2- alkylthio-5 （4）-（4-substitutedphenyl）imidazole-4（5）-yl]benzenesul fonamides （4a-4j）, which are intended to act as cyclooxygenase-2 （COX-2） inhibitors with good COX-2 inhibitor activity, and which will exert anti-inflammatory activities in vivo. Methods： Benzenesulfonamide derivatives were designed and synthesized through multi-step chemical reactions. All the synthesized compounds were evaluated in an in vitro assay. The active compound 4a-4f was selected for further evaluation in a carrageenan-induced rat paw edema model. Results： Docking studies showed that compound 4 bind into the primary binding site of COX-2 with the sulfonamide SO2NH2 moiety interacting with the secondary pocket amino acid residues. In the in vitro assay, compound 4 inhibited COX-2 with an inhibition concentration IC50 value of 1.23-8 nmol/L, compared to celecoxib with IC50 value of 1.5 nmol/L. Compound 4b and 4c had good potency and selectivity in comparison to the celecoxib. In the in vivo model, compound 4a-4f exhibited a moderate potency to inhibit 50% carrageenan-induced paw edema with value of 1.58-4.3 mg/kg. In the latter experiment, compound 4c was the most active compound. Conclusion： The antiinflammatory effects obtained for compound 4a-4j could be due to the presence of fluorine or hydrogen substituents in the para position of the phenyl ring of these compounds.     

The use of NSAIDs in rheumatic disorders 2005: a global perspective

Population studies and World Health Organisation (WHO) statistics indicate that 10-50% of individuals suffer from musculoskeletal disorders. Up to 3% will be classified as disabled due to their bone and joint condition, and the majority will suffer from pain. Almost all will require non-steroidal anti-inflammatory drugs (NSAIDs) and other analgesics for their management. The large majority of this population is elderly and, hence, at greater risk of adverse effects to the NSAIDs. The NSAIDs are a necessary choice in pain management because of the integrated role of the cyclo-oxygenase (COX) pathway in the generation of inflammation and in the biochemical recognition of pain. For over 80 years the management of musculoskeletal pain was hampered by NSAID toxicity problems related to the traditional NSAIDs. In the early 1990s, paracetamol was recommended as the first-choice analgesic for osteoarthritis, but subsequent studies have shown that paracetamol has a significant gastrointestinal (GI) toxicity profile. In addition, it has lower analgesic efficacy than NSAIDs and is, thus, not an effective alternative to NSAIDs in any of the inflammatory arthritides. The identification of cyclo-oxygenase 2 (COX-2) and the subsequent introduction of the COX-2-selective inhibitor NSAID drugs was thought to be a major breakthrough with the expectation of a significant reduction in G/I side-effects. This has not been the case for celecoxib, and indeed for all COX-2-selective inhibitors when given with ASA. The COX-2-selective inhibitors also inhibit renal COX-2 with the potential for problems of fluid retention, oedema, hypertension and congestive heart failure. The major controversy with respect to the COX-2-selective inhibitors as a class has been the increase in myocardial infarction and other cardiovascular events observed in some studies. Thus, the initial expected global benefits of the COX-2-selective inhibitors may be outweighed by their potential for toxicity. Recent studies have shown that the use of a proton-pump inhibitor drug with traditional NSAIDs and with COX-2-selective inhibitors has been shown to significantly reduce GI symptoms and peptic ulceration. Thus, the traditional NSAIDs have been re-established as the preferred choice in the management of arthritis and musculoskeletal disorders.     

4-substituted 1,5-diarylpyrazole,analogues of celecoxib: synthesis and preliminary evaluation of biological properties

A number of 5-aryl-1-[4-(methylsulfonyl)-phenyl]-1H-pyrazoles and 4-(5-aryl-1H-pyrazol-1-yl)benzenesulfonamides 3, 4, 5, 6, analogues of the COX-2 selective inhibitor celecoxib (celebrex), were synthesized. In order to verify the effects on the biological properties of certain substituents put on position 4 of the pyrazole nucleus, some of these compounds were screened in vivo for their anti-inflammatory and analgesic activities. Moreover, sodium salts of carboxylic acids 4 were tested in vitro for their platelet anti-aggregating properties. The results of these preliminary biological assays showed that new derivatives are not endowed with improved anti-inflammatory and analgesic properties, in comparison with celecoxib. In addition, docking studies were carried out on the most significative compounds to evaluate their interaction mode at the active site of both COX-1 and COX-2. Some remarks about the SAR of this class of COX-inhibitors are drown out.     

Synthesis and biological evaluation of pyrazolone analogues as potential anti-inflammatory agents targeting cyclooxygenases and 5-lipoxygenase

New pyrazolone derivatives structurally related to celecoxib and FPL 62064 were synthesized and biologically evaluated for their inhibitory activity against cyclooxygenases (COXs) and 5-lipoxygenase (5-LOX) and their selectivity indices were calculated. The results showed that compounds 3f , 3h , 3l , and 3p have an excellent COX-2 selectivity index. Moreover, they showed potent 5-LOX inhibitory activity relative to celecoxib and zileuton, as positive controls. These promising candidates were further investigated for anti-inflammatory activity using the carrageenan-induced rat paw edema method and ulcerogenic liability. The results showed no ulceration, which implies their gastric safety profile. Moreover, these compounds were evaluated for prostaglandin (PGE2) production in rat serum. Molecular docking in the COX-2 and 5-LOX active sites was performed to rationalize their anti-inflammatory activities. Strong binding interactions and effective docking scores were identified. The results indicated that these derivatives are good leads for dual-acting COX-2/5-LOX inhibitors to be used as potent and safe anti-inflammatory agents.     

Design, synthesis, and anti-inflammatory evaluation of a series of novel amino acid-binding 1,5-diarylpyrazole derivatives

Aim: To design and synthesize a series of novel amino acid-binding 1,5-diarylpyrazole derivatives, which are intended to act as prodrugs with better aqueous solubility than celecoxib, and which will exert potent anti-inflammatory activi-ties after being converted to their parent compounds in vivo. Methods: To introduce an amino acid, celecoxib analogs containing amino or methylamino group were synthesized first through multi-step chemical reactions. All the synthesized compounds were screened in an intact cell-based assay in vitro and in carrageenan-induced mouse paw edema in vivo. Some active compounds were selected for further evaluation in a carrageenan-induced rat paw edema model. The preliminary pharmacokinetics experiments were conducted using high performance liquid chromatography/mass spectrometry (HPLC/MS). Results: Celecoxib, 6 of the 1,5-diarylpyrazole class of celecoxib analogs, and their amino acid derivatives (hydrochloride salts) were synthesized. In vitro screening, the hydrochloride salts showed decreased inhibitory effects on cyclooxygenase (COX)- 1 and COX-2 compared with their parent compounds, but some exhibited potent anti-inflammatory activity in vivo. Compound 4a was selected for further evaluation, and its anti-inflammatory effect was equivalent to that of celecoxib after oral administration in the carrageenan-induced rat paw edema model. At three doses (25 mg/kg, 50 mg/kg, and 100 mg/kg) the percentage inhibition on edema was 20.7%, 52.6%, and 62.6% (for compound 4a) and 27.8%, 38.4%, and 40.1% (for celecoxib), respectively. Preliminary pharmacokinetic evaluations support the hypothesis that compound 4a was actually converted to its parent compound, compound 4. Conclusion: The compound bound with amino acid acts like prodrug, which can exert anti-inflammatory effect similar to celecoxib after being converted to its parent compound. This finding will be of great benefit in carrying out structural modifications of prodrug-like selective COX-2 inhibitors.     

New celecoxib derivatives as anti-inflammatory agents

A series of 1,5-diarylpyrazoles with a substituted benzenesulfonamide moiety was synthesized and evaluated for cyclooxygenase (COX-1/COX-2) inhibitory activities. Some compounds, for example, (+/-)-2-[4-(5- p-tolyl-3-trifluoromethyl-pyrazole-1-yl)-benzenesulfonylaminooxy]-propionic acid 16 and its disodium salt 21, had a higher in vivo anti-inflammatory activity compared to celecoxib, despite having no in vitro COX-1 or COX-2 inhibitory activity. Their gastrointestinal side effect profile is essentially more favorable than that of celecoxib.     

Additive interaction of intraperitoneal dexmedetomidine and topical nimesulide, celecoxib, and DFU for antinociception

Nimesulide, celecoxib, and DFU (5, 5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone) are nonsteroidal anti-inflammatory drugs (NSAIDs) with selective cyclo-oxygenase (COX)-2 blocking properties and have potent analgesic and anti-inflammatory activities in oral and parenteral administrations. Dexmedetomidine, a highly selective alpha(2)-adrenoceptor agonist, is an extremely potent antinociceptive agent. The present study was conducted to evaluate the antinociception induced by nimesulide, celecoxib, and DFU when topically applied on the tail in the absence or presence of intraperitoneal dexmedetomidine. Antinociception was measured in the radiant tail-flick test after immersion of the tail of rat into a solution of dimethyl sulfoxide (DMSO) containing nimesulide, celecoxib, or DFU. Antinociceptive effect of all drugs peaked at 60 min and decreased gradually to baseline levels at 240 min. Nimesulide had a potency lower than those of celecoxib, and DFU. The antinociceptive effect of dexmedetomidine was blocked by systemic pretreatment of selective alpha(2)-adrenoceptor antagonist, atipamezole. This suggests that antinociceptive effects of dexmedetomidine involve alpha(2)-adrenoceptors. Combination of topical COX-2 inhibitors with intraperitoneal dexmedetomidine yielded additive analgesic effect. These results demonstrate an additive interaction between topical COX-2 inhibitors with intraperitoneal dexmedetomidine. These observations are significant for physicians to combine selective COX-2 inhibitors and dexmedetomidine in the management of pain.     

The search for new COX-2 inhibitors: a review of 2002 – 2008 patents

Background: Two COX isoenzymes are known, COX-1 and COX-2, for which the main inhibitors are the NSAIDs. The common anti-inflammatory drugs (such as aspirin, ibuprofen and naproxen) all act by blocking the action of both the COX-1 and COX-2 enzymes. The COX-2 inhibitors represent a new class of drugs that do not affect COX-1 but selectively block COX-2. This selective action provides the benefits of reducing inflammation without irritating the stomach and cardiovascular effects. Objective: This review focuses on patents published in the field during 2002 – 2008, paying particular attention to promising COX-2 inhibitors. Conclusion: Structural analogues of the COX-2 inhibitors celecoxib and valdecoxib, and novel potential pyridazine, triazole, indole and thione derivatives emerge as promising leads for the treatment of inflammation, pain and other diseases.     

Selective cyclooxygenase-2 inhibitors: pharmacology, clinical effects and therapeutic potential

Since the discovery of a second isozyme of cyclooxygenase, COX-2, the field of prostaglandin and inflammation research has rapidly developed. It is becoming more evident that inhibition of COX-2 results in the analgesic and anti-inflammatory actions of non-steroidal anti-inflammatory drugs (NSAIDs), and that inhibition of COX-1 results in the adverse side-effects seen with these compounds. The mechanisms causing intestinal ulceration and renal toxicity are being elucidated, and large scale clinical trials with a preferential COX-2 inhibitor, meloxicam, and the first clinical results with highly selective COX-2 inhibitors, such as MK966 and celecoxib, support a superior benefit to risk ratio. In addition, important new areas where COX-2 expression is elevated, such as colonic cancer, have been identified and a role for COX-2 has also been proposed in Alzheimer's disease. Inhibition of COX-2 for these indications by selective COX-2 inhibitors may provide effective new therapies in the future.     

Selective cyclooxygenase-2 inhibitors: pharmacology,clinical effects and therapeutic potential

Since the discovery of a second isozyme of cyclooxygenase, COX-2, the field of prostaglandin and inflammation research has rapidly developed. It is becoming more evident that inhibition of COX-2 results in the analgesic and anti-inflammatory actions of non-steroidal anti-inflammatory drugs (NSAIDs), and that inhibition of COX-1 results in the adverse side-effects seen with these compounds. The mechanisms causing intestinal ulceration and renal toxicity are being elucidated, and large scale clinical trials with a preferential COX-2 inhibitor, meloxicam, and the first clinical results with highly selective COX-2 inhibitors, such as MK966 and celecoxib, support a superior benefit to risk ratio. In addition, important new areas where COX-2 expression is elevated, such as colonic cancer, have been identified and a role for COX-2 has also been proposed in Alzheimer’s disease. Inhibition of COX-2 for these indications by selective COX-2 inhibitors may provide effective new therapies in the future.     

Cyclooxygenase-1-selective inhibitors are attractive candidates for analgesics that do not cause gastric damage. design and in vitro/in vivo evaluation of a benzamide-type cyclooxygenase-1 selective inhibitor

Although cyclooxygenase-1 (COX-1) inhibition is thought to be a major mechanism of gastric damage by nonsteroidal anti-inflammatory drugs (NSAIDs), some COX-1-selective inhibitors exhibit strong analgesic effects without causing gastric damage. However, it is not clear whether their analgesic effects are attributable to COX-1-inhibitory activity or other bioactivities. Here, we report that N-(5-amino-2-pyridinyl)-4-(trifluoromethyl)benzamide ( 18f, TFAP), which has a structure clearly different from those of currently available COX-1-selective inhibitors, is a potent COX-1-selective inhibitor (COX-1 IC 50 = 0.80 +/- 0.05 microM, COX-2 IC 50 = 210 +/- 10 microM). This compound causes little gastric damage in rats even at an oral dose of 300 mg/kg, though it has an analgesic effect at as low a dose as 10 mg/kg. Our results show that COX-1-selective inhibitors can be analgesic agents without causing gastric damage.     

Cyclooxygenase-2 inhibitors. 1,5-diarylpyrrol-3-acetic esters with enhanced inhibitory activity toward cyclooxygenase-2 and improved cyclooxygenase-2/cyclooxygenase-1 selectivity

The important role of cyclooxygenase-2 (COX-2) in the pathogenesis of inflammation and side effect limitations of current COX-2 inhibitor drugs illustrates a need for the design of new compounds based on alternative structural templates. We previously reported a set of substituted 1,5-diarylpyrrole derivatives, along with their inhibitory activity toward COX enzymes. Several compounds proved to be highly selective COX-2 inhibitors and their affinity data were rationalized through docking simulations. In this paper, we describe the synthesis of new 1,5-diarylpyrrole derivatives that were assayed for their in vitro inhibitory effects toward COX isozymes. Among them, the ethyl-2-methyl-5-[4-(methylsulfonyl)phenyl]-1-[3-fluorophenyl]-1H-pyrrol-3-acetate (1d), which was the most potent and COX-2 selective compound, also showed a very interesting in vivo anti-inflammatory and analgesic activity, laying the foundations for developing new lead compounds that could be effective agents in the armamentarium for the management of inflammation and pain.     

Design,synthesis, and biological evaluation of new pyrazoloquinazoline derivatives as dual COX-2/5-LOX inhibitors

A new series of pyrazoloquinazoline derivatives equipped with different chalcones was designed, synthesized, and identified through ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and infrared spectroscopic techniques. Our design strategy of the quinazolinone-privileged scaffold as a new scaffold was based on merging pharmacophores previously reported to exhibit cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LOX) inhibitory activity. All the newly synthesized derivatives were biologically evaluated for COX and 5-LOX inhibitory activity and COX-2 selectivity, using celecoxib and zileuton as reference drugs, as they exhibited promising anti-inflammatory activity. Compound 3j was found to be the most promising derivative, with IC₅₀ values of 667 and 47 nM against COX-1 and COX-2, respectively, which are superior to that of celecoxib (IC₅₀ value against COX-2 = 95 nM), showing an SI of 14.2 that was much better than celecoxib. Compounds 3f and 3h exhibited COX-1 inhibition, with IC₅₀ values of 1,485 and 684 nM, respectively. The synthesized compounds showed a significant inhibitory activity against 5-LOX, with IC₅₀ values ranging from 0.6 to 4.3 µM, where compounds 3f and 3h were found to be the most potent derivatives, with IC₅₀ values of 0.6 and 1.0 µM, respectively, in comparison with that of zileuton (IC₅₀ = 0.8 µM). These promising derivatives, 3f , 3h , and 3j , were further investigated in vivo for anti-inflammatory, gastric ulcerogenic effects, and prostaglandin production (PGE2) in rat serum. The molecular docking studies concerning the binding sites of COX-2 and 5-LOX revealed similar orientation, compared with reported inhibitors, which encouraged us to design new leads targeting COX-2 and 5-LOX as dual inhibitors, as a new avenue in anti-inflammatory therapy.     

Design,synthesis, and biological evaluation of new 1,4-diarylazetidin-2-one derivatives (β-lactams) as selective cyclooxygenase-2 inhibitors

A new series of 1,4-diarylazetidin-2-one derivatives (β-lactams) were designed and synthesized to evaluate their biological activities as selective cyclooxygenase-2 (COX-2) inhibitors. In vitro COX-1 and COX-2 inhibition studies showed that all compounds were selective inhibitors of the COX-2 isozyme with IC₅₀ values in the 0.05–0.11 µM range, and COX-2 selectivity indexes in the range of 170–703.7. Among the synthesized β-lactams, 3-methoxy-4-(4-(methylsulfonyl)phenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one ( 4j ) possessing trimethoxy groups at the N-1 phenyl ring exhibited the highest COX-2 inhibitory selectivity and potency, even more potent than the reference drug celecoxib. The analgesic activity of the synthesized compounds was also determined using the formalin test. Compound 4f displayed the best analgesic activity among the synthesized molecules. Molecular modeling studies indicated that the methylsulfonyl pharmacophore group can be inserted into the secondary pocket of the COX-2 active site for interactions with Arg⁵¹³. The structure–activity data acquired indicate that the β-lactam ring moiety constitutes a suitable scaffold to design new 1,4-diarylazetidin-2-ones with selective COX-2 inhibitory activity.     

Hydrogen sulfide-based therapies: focus on H2S releasing NSAIDs

Nonsteroidal anti-inflammatory pain medications, commonly referred to as NSAIDs, are effective treatment for pain, fever and inflammation. However their use associates with a 4-6 fold increase in the risk of gastrointestinal bleeding. The basic mode of action of NSAIDs lies in the inhibition of cyclooxygenases (COXs), a family of enzymes involved in the generation of prostaglandins (PGs). The COX exists at least in two isoforms, COX-1 and COX-2, with PGs mediating inflammation at site of injury generated by the COX-2, while COX-1 produces PGs that are essential in maintaining integrity in the gastrointestinal tract. Selective inhibitors of COX-2, the coxibs, spare the gastrointestinal tract while exerting anti-inflammatory and analgesic effects. However, their use has been linked to an increased risk of thrombo-embolic events. Nitric oxide (NO) and hydrogen sulfide (H(2)S), are potent vasodilatory agents that maintain mucosal integrity in the gastrointestinal tract. In the last decade hybrid molecules that release NO or H(2)S have been coupled with non-selective NSAIDs to generate new classes of anti-inflammatory and analgesic agents with the potential to spare the gastrointestinal and cardiovascular system. These agents, the NO-releasing NSAIDs, or CINOD, and the H(2)S-releasing NSAIDs are currently investigated as a potential alternative to NSAIDs and coxibs. Naproxcinod has been the first, and so far the only, CINOD extensively investigated in clinical trials. Despite its promising profile, the approval of this drug was recently rejected by the Food and Drug Administration because the lack of long-term controlled studies. NSAIDs that release H(2)S as a mechanism to support an enhanced gastrointestinal and cardiovascular safety are being investigated in preclinical studies. Either naproxen or diclofenac coupled to an H(2)S releasing moiety has been reported to cause less gastrointestinal and cardiovascular injury than parent NSAIDs in preclinical models.