Direct gas measurements indicate that the novel cyclooxygenase inhibitor AZD3582 is an effective nitric oxide donor in vivo

Formation of new bioactive organic nitrites and their identification with gas chromatography-mass spectrometry and liquid chromatography coupled to nitrite reduction

Nitric oxide (NO) donors, notably organic nitrates and nitrites are used therapeutically but tolerance develops rapidly, making the use of e.g. nitroglycerin difficult. NO donation in the pulmonary vascular bed might be useful in critically ill patients. Organic nitrites are not associated with tachyphylaxis but may induce methaemoglobinemia and systemic hypotension which might hamper their use. We hypothesised that new lung-selective NO donors can be identified by utilizing exhaled NO as measure for pulmonary NO donation and systemic arterial pressure to monitor hypotension and tolerance development. Solutions of alcohols and carbohydrates were reacted with NO gas and administered to ventilated rabbits for evaluation of in vivo NO donation. Chemical characterization was made by liquid chromatography with on-line nitrite reduction (LC-NO) and by gas chromatography-mass spectrometry (GC-MS). In vivo experiments showed that the hydroxyl-containing compounds treated with NO gas yielded potent NO donors, via nitrosylation to organic nitrites. Analyses by LC-NO showed that the reaction products were able to release NO in vitro. In GC-MS the reaction products were determined to be the organic nitrites, where some are new chemical entities. Non-polar donors preferentially increased exhaled NO with less effect on systemic blood pressure whereas more polar molecules had larger effects on systemic blood pressure and less on exhaled NO. We conclude that new organic nitrites suitable for intravenous administration are produced by reacting NO gas and certain hydroxyl-containing compounds in aqueous solutions. Selectivity of different organic nitrites towards the pulmonary and systemic circulation, respectively, may be determined by molecular polarity.

Clinical pharmacokinetics of the cyclooxygenase inhibiting nitric oxide donator (CINOD) AZD3582

The clinical pharmacokinetics of the COX-inhibiting nitric oxide donator (CINOD) AZD3582 and its metabolites, including naproxen, nitric oxide and nitrate, are summarized. AZD3582 has low aqueous solubility, moderate and passive intestinal permeability and is degraded by intestinal esterases. Its oral bioavailability (F) appears to be maximally a few per cent, and increases by several-fold after food intake. Ninety-four per cent or more of an AZD3582 dose is absorbed, of which at least 9–20% appears to be taken up as intact substance. AZD3582 has a predicted plasma protein binding degree of ∼ 0.1%, a half-life (t½) of 3 to 10 h and does not accumulate after repeated once- and twice-daily dosing. In patients AZD3582 does not provide a significantly better gastrointestinal (GI) side-effect profile than the highly permeable and locally irritating naproxen. Possible reasons for this include considerable GI uptake as naproxen, limited duration and extent of nitric oxide donation in the GI mucosa and the circulation, tolerance development (involving auto-inhibition of nitric oxide catalysing enzymes) and mucosal damage caused by nitric oxide. Blood pressure data suggest that nitric oxide is mainly donated within 3h. The uptake of naproxen is slightly slower and lower (≥ 94% relative GI uptake and 80–85% relative F) after AZD3582 administration compared with naproxen dosing. The naproxen t½ and trough steady-state concentrations after AZD3582 and naproxen dosing are similar. The average systemic nitrate exposure is approximately doubled after dosing of 375 to 750 mg AZD3582 twice daily.

Deficiency of mitogen-activated protein kinase phosphatase-1 results in iNOS-mediated hypotension in response to low-dose endotoxin

Mitogen-activated protein kinase phosphatase-1 (MKP-1) is essential in limiting the proinflammatory response to lipopolysaccharide (LPS). We hypothesized that Mkp-1(-/-) mice would respond to low-dose LPS with a fall in blood pressure due to augmented expression of inducible nitric oxide (NO) synthase (iNOS). To test this hypothesis, Mkp-1(-/-) mice and their wild-type littermates were treated with 10 microg/kg iv LPS, and mean arterial blood pressure (MAP) and exhaled NO production (exNO) were measured. Tissues were harvested for an assessment of iNOS protein levels. Wild-type mice had no change in MAP or exNO during the experimental period, whereas Mkp-1(-/-) mice had a fall (P < 0.005) in MAP [79 +/- 5% of baseline (BL)] and an increase (P < 0.01) in exNO (266 +/- 50% of BL) after 150 min. The tissue levels of iNOS were greater in Mkp-1(-/-) than in wild-type mice. In additional experiments, 60 min after LPS treatment, Mkp-1(-/-) and wild-type mice were given N(omega)-nitro-l-arginine methyl ester (l-NAME) or aminoguanidine, and MAP and exNO were monitored for 90 min. Treatment with l-NAME prevented the LPS-induced increase in exNO and decrease in MAP but resulted in decreased exNO and elevated MAP in wild-type mice. Aminoguanidine prevented the increase in exNO and the fall in MAP caused by LPS in Mkp-1(-/-) mice, without significantly affecting MAP or exNO in wild-type mice. These results demonstrate that a deficiency of MKP-1 results in an exaggerated hypotensive response to LPS mediated by augmented iNOS expression. We speculate that defects in the Mkp-1 gene may increase susceptibility for the development of septic shock.

Gastroduodenal mucosal defense

PURPOSE OF REVIEW

The duodenum absorbs nearly all secreted gastric acid. Carbonic anhydrases facilitate transmucosal acid movement. The upper gastrointestinal tract must resist a variety of injuries, including those caused by ingested noxious substances, acid, ischemia/reperfusion, and infections such as Helicobacter pylori. The results are similar, however, regardless of insult: inflammation, ulceration, or metaplasia/dysplasia. In the past year, there have been prominent findings suggesting that oxidative stress and the formation of reactive oxygen species may play a pivotal role in all forms of injury, and that antioxidants may be the key to injury prevention and healing.

RECENT FINDINGS

Oxidative injury may be a common mechanism by which the upper gastrointestinal mucosa responds to noxious insults. Endogenous antioxidants, such as ghrelin, L-carnitine, and annexin-1 attenuate the oxidative-stress response. Similarly, exogenous antioxidants have also been shown to decrease inflammation, upregulate free radical scavengers, and prevent the formation of reactive oxygen species.

SUMMARY

Many studies published in the past year have linked oxidative stress to a variety of upper gastrointestinal insults. Exogenous and endogenous antioxidant compounds prevent the oxidative stress response. The future holds great promise for the development of pharmaceuticals with antioxidant properties that are safe, efficacious, and inexpensive.

Analgesic efficacy of the cyclooxygenase-inhibiting nitric oxide donor AZD3582 in postoperative dental pain: Comparison with naproxen and rofecoxib in two randomized, double-blind, placebo-controlled studies

OBJECTIVE

This study assessed the analgesic efficacy of single doses of 4-(nitrooxy)butyl-(2S)-2-(6-methoxy-2-naphthyl) propanoate (AZD3582) in acute postoperative dental pain after the removal of an impacted mandibular third molar (ie, wisdom tooth).

METHODS

Two randomized, placebo-controlled, double-blind studies were performed. In a dose-finding study, 242 patients were randomized to AZD3582 375, 750, 1500, or 2250 mg (n = 41, 37, 42, and 41, respectively); naproxen 500 mg (n = 39); or placebo (n = 42). In a comparator study, 282 patients were randomized to AZD3582 500 mg (n = 78) or 750 mg (n = 83), rofecoxib 50 mg (n = 80), or placebo (n = 41). Primary outcomes included time to rescue medication, time to pain relief, and mean pain intensity difference (MPID), as well as safety profile. Pain was rated on a visual analog scale.

RESULTS

In the dose-finding study, 52% (126/242) were women; the mean (SD) age was 25.1 (4) years, mean weight was 69.0 kg, and the mean (SD) body mass index (BMI) was 23.7 (3) kg/m2. In the comparator study, 58% (164/282) were women; the mean (SD) age was 27 (6.4) years, mean weight was 71 kg, and mean (SD) BMI was 24.2 (3) kg/m2. In the dose-finding study, the AZD3582 750-, 1500-, and 2250-mg groups were superior to placebo in the primary variables "time to rescue medication (0-8 hours)" (hazard ratios [HRs] [95% CIs], 0.17 [0.07-0.42], P < 0.003; 0.23 [0.11-0.50], P < 0.001; and 0.15 [0.06-0.36], P < 0.001, respectively), "time to meaningful pain relief" (HRs [95% CIs], 3.42 [1.87-6.25], P < 0.003; 2.49 [1.37-4.50], P < 0.003; and 3.07 [1.70-5.55], P < 0.001, respectively), and MPID (analysis of covariance [ANCOVA] least squares mean [LSM] differences [95% CIs], 25.8 [17.3-34.4], P < 0.003; 20.4 [12.1-28.7], P < 0.003; and 29.3 [20.9-37.6], P < 0.001, respectively). AZD3582 and naproxen did not show any statistically significant differences for the 3 primary variables, except that naproxen was superior to the AZD3582 375-mg dose for the variables time to meaningful pain relief (HR difference, 0.48 [95% CI, 0.29-0.78], P < 0.004) and MPID (difference in ANCOVA LSM, -10.2, [95% CI, -18.2 to -2.2], P < 0.012). The median times to meaningful pain relief were 115 minutes for AZD3582 375 mg, 66 minutes for 750 mg, 85 minutes for 1500 mg, 81 minutes for 2250 mg, and 162 minutes for placebo (P = NS, P = 0.003, P < 0.003, and P < 0.001, respectively). The median time to first rescue medication was 144 minutes for placebo, and <50% of the subjects on any of the AZD3582 doses or naproxen took rescue medication within 8 hours after dosing. In the comparator study, AZD3582 750 mg was superior to placebo in "time to rescue medication (0-24 hours)" (HR [95% CI], 0.4 [0.3-0.6], P < 0.001), "time to confirmed perceptible pain relief" (2.1 [1.1-3.8], P = 0.02), and MPID (11.9 [4.2-19.5], P = 0.002). However, inferiority of AZD3582 to rofecoxib for MPID could not be excluded (tolerance limit of 10 mm; P = NS for noninferiority testing). The median times to confirmed perceptible pain relief were 45 minutes for AZD3582 500 mg, 40 minutes for 750 mg, and 37 minutes for rofecoxib. The median times to first rescue medication were 218 minutes for AZD3582 500 mg, 365 minutes for 750 mg, 635 minutes for rofecoxib, and 90 minutes for placebo. Overall, AZD3582 was well tolerated. However, an effect on orthostatic blood pressure could not be excluded because there seemed to be more subjects with dizziness and orthostatic blood pressure reduction who were administered AZD3582 > or =750 mg. The proportions of patients with vertigo and decreased orthostatic blood pressure each group were as follows: AZD3582 500 mg, 6%; AZD3582 750 mg, 12%; rofecoxib, 3%; and placebo, 5%.

CONCLUSIONS

AZD3582 750 mg had similar analgesic efficacy as equimolar doses of naproxen, but noninferiority to rofecoxib was not demonstrated.

Nitric oxide-modulating agents for gastrointestinal disorders

Almost 20 years after the identification of the biological role of nitric oxide (NO), the full therapeutic potential of novel agents that mimic the activity of NO or interfere with its synthesis has yet to be realised for utilities involving the gastrointestinal tract. New utilities for classical NO donors, which were used as vasodilators for decades, in the treatment of motility disorders have been explored and a product for treating anal fissure was recently launched. New classes of compounds incorporating a NO-donating moiety into standard non-steroidal anti-inflammatory drugs, the NO-non-steroidal anti-inflammatory drugs (NO-NSAIDs) or COX-inhibiting nitric oxide donors (CINODs) have also been developed. These have been shown to exhibit reduced gastrointestinal injury in experimental models, and reports on their efficacy and safety in Phase I and II studies are now available. Modulation of the inducible NO synthase isoform that generates excessive NO that can lead to subsequent cytotoxic moieties, such as peroxynitrite, may have therapeutic possibilities in a range of inflammatory diseases of the gut. Likewise, agents that promote the decomposition of peroxynitrite or removal of its other component, superoxide, may also prove to be of use. Further targets for pharmaceutical exploitation are likely to come from both genomic and molecular insights into the processes that regulate the NO system.

Comparison of the COX-inhibiting nitric oxide donator AZD3582 and rofecoxib in treating the signs and symptoms of Osteoarthritis of the knee

OBJECTIVE

To compare the efficacy, safety, and tolerability of AZD3582 with that of rofecoxib, naproxen, and placebo in patients with osteoarthritis (OA) of the knee, and to define the dosage of AZD3582 (125 mg, 375 mg, and 750 mg twice a day) that is noninferior in efficacy to rofecoxib.

METHODS

A double-blind study of 672 patients with OA of the knee was conducted. Patients who experienced increased pain on withdrawal of analgesia were randomized to receive AZD3582 125 mg, 375 mg, or 750 mg twice a day; rofecoxib 25 mg once a day; naproxen 500 mg twice a day; or placebo for 6 weeks. Efficacy, tolerability, and safety were monitored throughout the study. The primary variable was the change in Western Ontario and McMaster Universities Osteoarthritis Index pain subscale from baseline to the mean of weeks 4 and 6, comparing AZD3582 with placebo for superiority and with rofecoxib for noninferiority using a predefined margin of 10 mm.

RESULTS

For the primary variable, AZD3582 375 mg and 750 mg were superior to placebo (least squares mean difference [95% confidence interval] -12 mm [-18, -6], P < 0.001 and -13 mm [-19, -7], P < 0.001, respectively) and were noninferior to rofecoxib (-2 mm [-8, 4], P < 0.001 and -3 mm [-9, 3], P < 0.001, respectively). AZD3582 125 mg was not significantly different from placebo for the primary variable.

CONCLUSION

AZD3582 375 mg and 750 mg twice a day were superior to placebo and as effective as rofecoxib 25 mg/day in treating the signs and symptoms of OA of the knee. AZD3582 125 mg twice a day was not statistically different from placebo.