Memantine for Pediatric Patients Receiving Cranial Irradiation: A Pilot Study

PURPOSE/OBJECTIVE(S)

While memantine has become standard in certain adults receiving brain RT to decrease the cognitive impacts of RT, it is unknown whether pediatric patients can take and tolerate memantine or experience benefit. In this prospective single-arm feasibility study, we hypothesized pediatric patients receiving brain RT would tolerate memantine with good treatment adherence.

MATERIALS/METHODS

Patients aged 4-18 years with a primary CNS malignancy (excluding WHO Grade IV astrocytoma and glioblastoma) receiving intracranial RT were eligible. A 6-month course of memantine was given during and after RT. Dosing began once daily at 5 mg with up-titration in 5 mg increments over 4 weeks to a weight-based maximum (0.4 mg/kg to the closest 5 mg), not to exceed 10 mg BID. To reduce patient and clinical research associate (CRA) burden, medication adherence was tracked via the Medisafe Pill and Reminder application which study staff helped install on the patient or parent's smart phone. A paper pill diary was provided for those unable to use the app. The primary endpoint was to achieve 80% adherence rate to memantine in 80% of patients measured 1-month post-RT.

RESULTS

Eighteen patients (14 male and 4 female, median age 11.5 years (range: 4-18)) were enrolled from 2020-2022. The study closed early after enrolling 18 of 20 planned patients to avoid competing with the phase III randomized Children's Oncology Group (COG) study AACL2031. One patient withdrew for cognition-altering substance-use, leaving 17 patients with data available for analysis. Histologies included germ cell tumor (n = 6), craniopharyngioma (n = 3), choroid plexus papilloma (n = 2), ependymoma (n = 2), glial/astrocytoma (n = 2), medulloblastoma (n = 1), and meningioma (n = 1). Thirteen had surgery, and 9 received chemotherapy. Eight received craniospinal irradiation (CSI). Median RT dose was 54 Gy (range 36-59.4) in 30 fractions (range: 20-33). At data freeze, all 17 had passed the 1-month post-RT time point. One patient discontinued memantine after a single dose due to nausea. Pill-reports were available for 14 of the remaining 16; two patients did not complete digital pill logs. For those with complete logs, all adherence rates were above 80%, with a median of 99.32% pill completion rate (range: 92.67-100). Seven (50%) took 100% of prescribed doses. Irrespective of adherence for the 2 unavailable for evaluation, the primary endpoint was still achieved. Grade 1 toxicities included headache (n = 6, 35%) and constipation (n = 1, 6%); there were no grade 2+ toxicities. At last follow-up, 15/16 have completed the full 6-month memantine course. Secondary endpoints including neurocognitive evaluations have not yet been met and will be the subject of future reports.

CONCLUSION

Memantine is a feasible and well-tolerated addition to multi-modality treatment for pediatric brain tumors. Secondary endpoints of this study and results of the ongoing COG study are awaited to define the value of memantine in this population.

Pharmacological SARM1 inhibition protects axon structure and function in paclitaxel-induced peripheral neuropathy

Axonal degeneration is an early and ongoing event that causes disability and disease progression in many neurodegenerative disorders of the peripheral and central nervous systems. Chemotherapy-induced peripheral neuropathy (CIPN) is a major cause of morbidity and the main cause of dose reductions and discontinuations in cancer treatment. Preclinical evidence indicates that activation of the Wallerian-like degeneration pathway driven by sterile alpha and TIR motif containing 1 (SARM1) is responsible for axonopathy in CIPN. SARM1 is the central driver of an evolutionarily conserved programme of axonal degeneration downstream of chemical, inflammatory, mechanical or metabolic insults to the axon. SARM1 contains an intrinsic NADase enzymatic activity essential for its pro-degenerative functions, making it a compelling therapeutic target to treat neurodegeneration characterized by axonopathies of the peripheral and central nervous systems. Small molecule SARM1 inhibitors have the potential to prevent axonal degeneration in peripheral and central axonopathies and to provide a transformational disease-modifying treatment for these disorders.

Using a biochemical assay for SARM1 NADase we identified a novel series of potent and selective irreversible isothiazole inhibitors of SARM1 enzymatic activity that protected rodent and human axons in vitro. In sciatic nerve axotomy, we observed that these irreversible SARM1 inhibitors decreased a rise in nerve cADPR and plasma neurofilament light chain released from injured sciatic nerves in vivo. In a mouse paclitaxel model of CIPN we determined that Sarm1 knockout mice prevented loss of axonal function, assessed by sensory nerve action potential amplitudes of the tail nerve, in a gene-dosage-dependent manner. In that CIPN model, the irreversible SARM1 inhibitors prevented loss of intraepidermal nerve fibres induced by paclitaxel and provided partial protection of axonal function assessed by sensory nerve action potential amplitude and mechanical allodynia.

Co-acting gene networks predict TRAIL responsiveness of tumour cells with high accuracy

Background

Identification of differentially expressed genes from transcriptomic studies is one of the most common mechanisms to identify tumor biomarkers. This approach however is not well suited to identify interaction between genes whose protein products potentially influence each other, which limits its power to identify molecular wiring of tumour cells dictating response to a drug. Due to the fact that signal transduction pathways are not linear and highly interlinked, the biological response they drive may be better described by the relative amount of their components and their functional relationships than by their individual, absolute expression.

Results

Gene expression microarray data for 109 tumor cell lines with known sensitivity to the death ligand cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was used to identify genes with potential functional relationships determining responsiveness to TRAIL-induced apoptosis. The machine learning technique Random Forest in the statistical environment “R” with backward elimination was used to identify the key predictors of TRAIL sensitivity and differentially expressed genes were identified using the software GeneSpring. Gene co-regulation and statistical interaction was assessed with q-order partial correlation analysis and non-rejection rate. Biological (functional) interactions amongst the co-acting genes were studied with Ingenuity network analysis. Prediction accuracy was assessed by calculating the area under the receiver operator curve using an independent dataset. We show that the gene panel identified could predict TRAIL-sensitivity with a very high degree of sensitivity and specificity (AUC = 0 · 84). The genes in the panel are co-regulated and at least 40% of them functionally interact in signal transduction pathways that regulate cell death and cell survival, cellular differentiation and morphogenesis. Importantly, only 12% of the TRAIL-predictor genes were differentially expressed highlighting the importance of functional interactions in predicting the biological response.

Conclusions

The advantage of co-acting gene clusters is that this analysis does not depend on differential expression and is able to incorporate direct- and indirect gene interactions as well as tissue- and cell-specific characteristics. This approach (1) identified a descriptor of TRAIL sensitivity which performs significantly better as a predictor of TRAIL sensitivity than any previously reported gene signatures, (2) identified potential novel regulators of TRAIL-responsiveness and (3) provided a systematic view highlighting fundamental differences between the molecular wiring of sensitive and resistant cell types.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1144) contains supplementary material, which is available to authorized users.

Discovery and optimization of 1-(4-(pyridin-2-yl)benzyl)imidazolidine-2,4-dione derivatives as a novel class of selective cannabinoid CB2 receptor agonists

Here, we report the identification and optimization of 1-(4-(pyridin-2-yl)benzyl)imidazolidine-2,4-dione derivatives as a novel chemotype with selective cannabinoid CB2 receptor agonist activity. 1 is a potent and selective cannabinoid CB2 receptor agonist (hCB2 pEC(50) = 8.6). The compound was found to be metabolically unstable, which resulted in low oral bioavailability in rat (F(po) = 4%) and possessed off-target activity at the hERG ion channel (pK(i) = 5.5). Systematic modification of physicochemical properties, such as lipophilicity and basicity, was used to optimize the pharmacokinetic profile and hERG affinity of this novel class of cannabinoid CB2 receptor agonists. This led to the identification of 44 as a potent, selective, and orally bioavailable cannabinoid CB2 receptor agonist (hCB2 pEC(50) = 8.0; hERG pK(i) < 4; F(po) = 100%), which was active in a rat spinal nerve ligation model of neuropathic pain.

Epidermal lipid metabolism of cultured skin substitutes during healing of full-thickness wounds in athymic mice

Cultured epidermal keratinocytes provide an abundant supply of biologic material for wound treatment. Because restoration of barrier function is a definitive criterion for efficacy of wound closure and depends on the lipids present in the epidermis, we analyzed lipid composition of the epidermis in cultured skin substitutes in vitro and after grafting to athymic mice. The cultured skin substitutes were prepared from human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates. After 14 days of incubation, cultured skin substitutes were grafted orthotopically onto full-thickness wounds in athymic mice. Samples for lipid analysis were collected after 14 and 34 days of in vitro incubation, and 3 weeks and 4 months after grafting. Both in vitro samples show disproportions in epidermal lipid profile as compared with the native human epidermis, i.e., a low amount of phospholipids (indicating imbalance in proliferation and differentiation); a large excess of triglycerides (storage lipids); and low levels of free fatty acids, gluco-sphingolipids, cholesterol sulfate, and ceramides-suggesting abnormal composition of stratum corneum barrier lipids. Fatty acid analysis of cultured skin substitutes in vitro revealed insufficient uptake of linoleic acid, which resulted in increased synthesis of and substitution with monounsaturated fatty acids, mainly oleic acid. These abnormalities were partially corrected by 3 weeks after grafting; and 4 months after grafting, all epidermal lipids, with some minor exceptions, were synthesized in proportions very similar to human epidermis. Results of this study show that grafting of cultured skin substitutes to a physiologic host permits the recovery of lipid in proportion to that required for barrier formation in normal human epidermis.

Risk of cancer treatment-related osteoporosis and fractures among women with breast cancer receiving aromatase inhibitors

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Background: Aromatase inhibitors (AIs) are a novel hormonal therapy for breast cancer. However, AIs can cause bone loss by blocking estrogen production. This study aims to assess the association between AIs and treatment-related bone loss in a large managed care population of women with breast cancer. Methods: Using medical and pharmacy claims data from over 5 million beneficiaries between 01/01/1998 and 01/31/2005, we identified 12,368 patients with ≥ 2 breast cancer claims in a 6-month period, who also had no bone metastasis and no prior osteoporosis or fracture claims. Patients who received anti-estrogen therapy were also excluded to remove the protective confounding effects. 1,354 patients receiving an AI (anastrozole, exemestane, letrozole) were compared to 11,014 controls who did not receive an AI with respect to their risk of bone loss. The observation start date for the AI and control groups was defined as the service date of the first AI claim and breast cancer claim, respectively. The bone loss endpoints analyzed were osteoporosis (including osteopenia) and clinical fractures. Results: The univariate analysis found that the prevalence of osteoporosis was 8.7% in the AI group vs. 7.1% in the control group, resulting in a statistically significant relative risk of 1.3 (95% CI=1.1–1.6, p=0.01). The prevalence of bone fracture was also statistically significantly elevated in the AI group compared to the controls (13.5% vs. 10.3%) with a relative risk of 1.4 (95% CI=1.2–1.6, p=0.001). Multivariate Cox proportional hazards regressions showed that after adjusting for age and comorbidities, the risk of bone loss remained statistically significantly higher in the AI group than the non-AI group, with 27% (95% CI=4%-55%, p=0.02) and 21% (95% CI=3%-43%, p=0.02) increase in the risk of osteoporosis and fractures, respectively. Conclusions: This retrospective longitudinal analysis of a large cohort of breast cancer patients corroborates previous findings from smaller clinical trials and demonstrates that AI therapies carry an increased risk of bone loss. Monitoring and treatment management strategies to alleviate bone loss risk are warranted in women receiving AI for breast cancer.

[Table: see text]

The search for novel TRPV1-antagonists: From carboxamides to benzimidazoles and indazolones

Based on a series of diaryl amides the corresponding inverse amides have been found to be potent TRPV1 receptor antagonists. Benzimidazole and indazolone derivatives prepared retained good potency in vitro and indazolone 4a was identified as a novel TRPV1 receptor antagonist suitable for evaluating orally in animal models of analgesia.

Inhibition of acute nociceptive responses in rat spinal cord by a bradykinin B1 receptor antagonist

This study used behavioural and in vivo electrophysiological paradigms to examine the effects of systemic and spinal administration of a bradykinin B1 receptor antagonist, compound X, on acute nociceptive responses in the rat. In behavioural experiments, compound X significantly increased the latency to withdraw the hindpaw from a radiant heat source after both intravenous and intrathecal administration, without affecting motor performance on the rotarod. In electrophysiological experiments, both intravenous and direct spinal administration of compound X attenuated the responses of single dorsal horn neurones to noxious thermal stimulation of the hindpaw. These data show that the antinociceptive effects of a bradykinin B1 receptor antagonist are mediated, at least in part, at the level of the spinal cord and suggest a role for spinal bradykinin B1 receptors in acute nociception.

2,3-Diaminopyridine Bradykinin B1 Receptor Antagonists

Bradykinin B1 receptor antagonists embody a potentially novel approach for the treatment of chronic pain and inflammation. A series of 2,3-diaminopyridine B1 antagonists was optimized to have sub-nanomolar affinity and good pharmacokinetic properties. Lead compounds were shown to exhibit good efficacy in rabbit in vivo models of pain and inflammation.

P-Glycoprotein efflux reduces the brain concentration of the substance P (NK1 receptor) antagonists SR140333 and GR205171: a comparative study using mdr1a-/- and mdr1a+/+ mice

Investigation of the antidepressant-like actions of substance P (NK1 receptor) antagonists has been hindered by the few available compounds that bind with high affinity to the rat and mouse NK1 receptor, as these are the most commonly used preclinical species. The best available compounds for such studies are SR140333 and GR205171. However, SR140333 does not penetrate the central nervous system (CNS) after systemic administration, and GR205171 is active only at high doses, where unspecific pharmacological effects occur, so that changes in behaviour cannot be attributed to selective NK1 receptor blockade. These compounds may be substrates for P-glycoprotein (P-gp) and hence are actively excluded from the brain. The present studies used mdr1a-/- mice, a spontaneously occurring mutant that is deficient in P-gp, to examine the CNS penetration of SR140333 and GR205171. Following systemic administration of SR140333 and GR205171 (0.01-10 mg/kg i.v.), considerably higher drug concentrations were achieved in the brains of mdr1a-/- than in mdr1a+/+ mice, and this corresponded with a greater ability to inhibit NK1-agonist-induced behaviours in the mdr1a-/- mutants. Moreover, an NK1-receptor-specific inhibition of aggressive behaviour by GR205171 (10 mg/kg) could be demonstrated in mdr1a-/-, but not mdr1a+/+, mice. These findings suggest that P-gp deficient mice may have useful applications in behavioural pharmacology studies, especially when highly brain-penetrant compounds are not yet available.

Neurological phenotype and synaptic function in mice lacking the CaV1.3 alpha subunit of neuronal L-type voltage-dependent Ca2+ channels

Neuronal L-type calcium channels have been implicated in pain perception and neuronal synaptic plasticity. To investigate this we have examined the effect of disrupting the gene encoding the CaV1.3 (alpha 1D) alpha subunit of L-type Ca2+ channels on neurological function, acute nociceptive behavior, and hippocampal synaptic function in mice. CaV1.3 alpha 1 subunit knockout (CaV1.3 alpha 1(-/-)) mice had relatively normal neurological function with the exception of reduced auditory evoked behavioral responses and lower body weight. Baseline thermal and mechanical thresholds were unaltered in these animals. CaV1.3 alpha 1(-/-) mice were also examined for differences in N-methyl-D-aspartate (NMDA) receptor-dependent (100 Hz tetanization for 1 s) and NMDA receptor-independent (200 Hz in 100 microM DL-2-amino-5-phosphopentanoic acid) long-term potentiation within the CA1 region of the hippocampus. Both NMDA receptor-dependent and NMDA receptor-independent forms of long-term potentiation were expressed normally. Radioligand binding studies revealed that the density of (+)[3H]isradipine binding sites in brain homogenates was reduced by 20-25% in CaV1.3 alpha 1(-/-) mice, without any detectable change in CaV1.2 (alpha 1C) protein levels as detected using Western blot analysis. Taken together these data indicate that following loss of CaV1.3 alpha 1 subunit expression there is sufficient residual activity of other Ca2+ channel subtypes to support NMDA receptor-independent long-term potentiation and some forms of sensory behavior/function.

Discovery of a potent, non-peptide bradykinin B1 receptor antagonist

Bradykinin (BK) plays an important role in the pathophysiological processes accompanying pain and inflammation. Selective bradykinin B1 receptor antagonists have been shown to be anti-nociceptive in animal models and could be novel therapeutic agents for the treatment of pain and inflammation. We have explored chemical modifications in a series of dihydroquinoxalinone sulfonamides to evaluate the effects of various structural changes on biological activity. The optimization of a screening lead compound, facilitated by a homology model of the BK B1 receptor, culminated in the discovery of a potent human BK B1 receptor antagonist. Results from site-directed mutagenesis studies and experiments in an animal pain model are presented.

The substance P (NK1) receptor antagonist L-760735 inhibits fear conditioning in gerbils

The ability of the substance P (NK(1) receptor) antagonist (SPA) L-760735 to inhibit conditioned fear was assessed in gerbils using a four plate apparatus. Animals that had been treated with diazepam (3 mg/kg) or L-760735 (3 mg/kg) 30 min before a 3 min conditioning session in the apparatus exhibited a release of plate crossings during the retest session approximately 3 h later. Plate crossings were also increased when animals received diazepam or L-760735 30 min before the retest session. In contrast, fluoxetine and venlafaxine (30 mg/kg) did not exhibit anxiolytic-like effects. During the retest session, gerbils drummed their hind feet on the floor; this behaviour was not observed spontaneously in gerbils that were naïve to the apparatus. Foot drumming was abolished by pretreatment with L-760735 or diazepam (3 mg/kg) but was markedly increased following administration of fluoxetine or venlafaxine (30 mg/kg). Foot drumming elicited by aversive conditioning alone or in combination with fluoxetine was abolished by administration of L-760735 and by amygdala lesions involving the basolateral and lateral nuclei, indicating that this behaviour is an alarm signal or fear response mediated via release of substance P in brain circuits involving the amygdala. The observations provide further evidence for an anxiolytic-like profile of SPAs in preclinical assays and demonstrate a clear difference between the actions of SPAs and established antidepressant drugs.

Functional properties of the high-affinity TRPV1 (VR1) vanilloid receptor antagonist (4-hydroxy-5-iodo-3-methoxyphenylacetate ester) iodo-resiniferatoxin

We have synthesized iodinated resiniferatoxin bearing a 4-hydroxy-5-iodo-3-methoxyphenylacetate ester (I-RTX) and have characterized its activity on rat and human TRPV1 (VR1) receptors, as well as in behavioral assays of nociception. In whole cell patch-clamp recordings from transfected cells the functional activity of I-RTX was determined. Currents activated by capsaicin exhibited characteristic outward rectification and were antagonized by capsazepine and I-RTX. On rat TRPV1 the affinity of I-RTX was 800-fold higher than that of capsazepine (IC50 = 0.7 and 562 nM, respectively) and 10-fold higher on rat versus human receptors (IC50 = 0.7 and 5.4 nM, respectively). The same difference was observed when comparing the inhibition of [3H]RTX binding to rat and human TRPV1 membranes for both RTX and I-RTX. Additional pharmacological differences were revealed using protons as the stimulus. Under these conditions capsazepine only partly blocked currents through rat TRPV1 receptors (by 70 to 80% block), yet was a full antagonist on human receptors. In contrast, I-RTX completely blocked proton-induced currents in both species and that activated by noxious heat. I-RTX also blocked capsaicin-induced firing of C-fibers in a rat in vitro skin-nerve assay. Despite this activity and the high affinity of I-RTX for rat TRPV1, only capsazepine proved to be an effective antagonist of capsaicin-induced paw flinching in rats. Thus, although I-RTX has limited utility for in vivo behavioral studies it is a high-affinity TRPV1 receptor antagonist that will be useful to characterize the functional properties of cloned and native vanilloid receptor subtypes in vitro.

Increased mortality after coronary artery bypass graft surgery is associated with increased levels of postoperative creatine kinase-myocardial band isoenzyme release: results from the GUARDIAN trial

OBJECTIVES

We sought to determine if elevated cardiac serum biomarkers after coronary artery bypass graft surgery (CABG) are associated with increased medium-term mortality and to identify patients that may benefit from better postoperative myocardial protection.

BACKGROUND

The relationship between the magnitude of cardiac serum protein elevation and subsequent mortality after CABG is not well defined, partly because of the lack of large, prospectively studied patient cohorts in whom postoperative elevations of cardiac serum markers have been correlated to medium- and long-term mortality.

METHODS

The GUARD during Ischemia Against Necrosis (GUARDIAN) study enrolled 2,918 patients assigned to the entry category of CABG and considered as high risk for myocardial necrosis. Creatine kinase-myocardial band (CK-MB) isoenzyme measurements were obtained at baseline and at 8, 12, 16 and 24 h after CABG.

RESULTS

The unadjusted six-month mortality rates were 3.4%, 5.8%, 7.8% and 20.2% for patients with a postoperative peak CK-MB ratio (peak CK-MB value/upper limits of normal [ULN] for laboratory test) of < 5, > or = 5 to <10, > or =10 to < 20 and > or =20 ULN, respectively (p < 0.0001). The relationship remained statistically significant after adjustment for ejection fraction, congestive heart failure, cerebrovascular disease, peripheral vascular disease, cardiac arrhythmias and the method of cardioplegia delivery. Receiver operating characteristic curve analysis revealed an area under the curve of 0.648 (p < 0.001); the optimal cut-point to predict six-month mortality ranged from 5 to 10 ULN.

CONCLUSIONS

Progressive elevation of the CK-MB ratio in clinically high-risk patients is associated with significant elevations of medium-term mortality after CABG. Strategies to afford myocardial protection both during CABG and in the postoperative phase may serve to improve the clinical outcome.

Intra-amygdala injection of the substance P [NK(1) receptor] antagonist L-760735 inhibits neonatal vocalisations in guinea-pigs

The involvement of the basolateral amygdala in mediating the inhibition of neonatal vocalisation by substance P (NK(1) receptor) antagonists was examined. These studies determined whether the time course for separation-induced vocalisations in guinea-pig pups coincided with NK(1) receptor internalisation (a marker of substance P release) in the amygdala, and whether vocalisations could be blocked by focal injection of the NK(1) receptor antagonist L-760735 into this brain region. The peak period for neonatal vocalisations occurred 5-10 min following maternal separation. This coincided with the peak increase in the number of cells in the basolateral amygdala exhibiting NK(1) receptor endocytosis, consistent with the proposal that substance P is released in the amygdala as a result of isolation stress. Focal injection of L-760735 (15 nmol per side) but not L-770765 (an analogue of L-760735 which has low NK(1) receptor affinity) into the basolateral amygdala attenuated separation-induced vocalisations. In contrast, injection of L-760735 (15 nmol per side) into the dorsal ventricular nucleus of the thalamus, a region with relatively low density of NK(1) receptors, had no effect on neonatal vocalisations. These findings are consistent with other evidence that the amygdala is one possible site of action for the inhibition of neonatal vocalisations by substance P antagonists.

Clinical guidelines for the use of the prone position in acute respiratory distress syndrome

The mortality associated with acute respiratory distress syndrome (ARDS) remains high. It has been suggested that use of the prone position may improve survival. However, approaches to the use of the position are often haphazard. The development of clinical guidelines indicating the need for the prone position in ARDS and the process by which the manoeuvre may be performed were thought to be important for two reasons. Primarily, we sought to improve oxygenation through the use of the prone position whilst promoting patient safety. Secondly, we wished to standardize our approach to the use of the prone position and make recommendations for practice so that its use was no longer seen as a last resort in the management of ARDS. The process associated with the development of clinical guidelines is first described. This is followed by presentation of the clinical guidelines. Included in these are the criteria and discussion which indicate consideration of the prone position, potential exclusion criteria, pre-turn considerations, the turning technique, monitoring the effectiveness of the prone position, passive movements and limb positioning and, finally, documentation of the problems associated with use of the prone position. The paper concludes with discussion concerning the potential for future research in this area.

Etoricoxib (MK-0663): preclinical profile and comparison with other agents that selectively inhibit cyclooxygenase-2

We report here the preclinical profile of etoricoxib (MK-0663) [5-chloro-2-(6-methylpyridin-3-yl)-3-(4-methylsulfonylphenyl) pyridine], a novel orally active agent that selectively inhibits cyclooxygenase-2 (COX-2), that has been developed for high selectivity in vitro using whole blood assays and sensitive COX-1 enzyme assays at low substrate concentration. Etoricoxib selectively inhibited COX-2 in human whole blood assays in vitro, with an IC(50) value of 1.1 +/- 0.1 microM for COX-2 (LPS-induced prostaglandin E2 synthesis), compared with an IC(50) value of 116 +/- 8 microM for COX-1 (serum thromboxane B2 generation after clotting of the blood). Using the ratio of IC(50) values (COX-1/COX-2), the selectivity ratio for the inhibition of COX-2 by etoricoxib in the human whole blood assay was 106, compared with values of 35, 30, 7.6, 7.3, 2.4, and 2.0 for rofecoxib, valdecoxib, celecoxib, nimesulide, etodolac, and meloxicam, respectively. Etoricoxib did not inhibit platelet or human recombinant COX-1 under most assay conditions (IC(50) > 100 microM). In a highly sensitive assay for COX-1 with U937 microsomes where the arachidonic acid concentration was lowered to 0.1 microM, IC(50) values of 12, 2, 0.25, and 0.05 microM were obtained for etoricoxib, rofecoxib, valdecoxib, and celecoxib, respectively. These differences in potency were in agreement with the dissociation constants (K(i)) for binding to COX-1 as estimated from an assay based on the ability of the compounds to delay the time-dependent inhibition by indomethacin. Etoricoxib was a potent inhibitor in models of carrageenan-induced paw edema (ID(50) = 0.64 mg/kg), carrageenan-induced paw hyperalgesia (ID(50) = 0.34 mg/kg), LPS-induced pyresis (ID(50) = 0.88 mg/kg), and adjuvant-induced arthritis (ID(50) = 0.6 mg/kg/day) in rats, without effects on gastrointestinal permeability up to a dose of 200 mg/kg/day for 10 days. In squirrel monkeys, etoricoxib reversed LPS-induced pyresis by 81% within 2 h of administration at a dose of 3 mg/kg and showed no effect in a fecal 51Cr excretion model of gastropathy at 100 mg/kg/day for 5 days, in contrast to lower doses of diclofenac or naproxen. In summary, etoricoxib represents a novel agent that selectively inhibits COX-2 with 106-fold selectivity in human whole blood assays in vitro and with the lowest potency of inhibition of COX-1 compared with other reported selective agents.

Warm-coding deficits and aberrant inflammatory pain in mice lacking P2X3 receptors

ATP activates damage-sensing neurons (nociceptors) and can evoke a sensation of pain. The ATP receptor P2X3 is selectively expressed by nociceptors and is one of seven ATP-gated, cation-selective ion channels. Here we demonstrate that ablation of the P2X3 gene results in the loss of rapidly desensitizing ATP-gated cation currents in dorsal root ganglion neurons, and that the responses of nodose ganglion neurons to ATP show altered kinetics and pharmacology resulting from the loss of expression of P2X(2/3) heteromultimers. Null mutants have normal sensorimotor function. Behavioural responses to noxious mechanical and thermal stimuli are also normal, although formalin-induced pain behaviour is reduced. In contrast, deletion of the P2X3 receptor causes enhanced thermal hyperalgesia in chronic inflammation. Notably, although dorsal-horn neuronal responses to mechanical and noxious heat application are normal, P2X3-null mice are unable to code the intensity of non-noxious 'warming' stimuli.

Analgesic and toxic effects of ABT-594 resemble epibatidine and nicotine in rats

The present study directly compared the antinociceptive and toxic effects of the neuronal nicotinic receptor agonist ABT-594 ((R)-5-(2-azetidinylmethoxy)-2-chloropyridine) with (-)-nicotine and (+)-epibatidine. Like (-)-nicotine (0.8 and 1.6 mg/kg s.c.) and (+)-epibatidine (0.005 and 0.01 mg/kg s.c.), ABT-594 (0.05 and 0.1 mg/kg s.c.) increased response latencies in the hot-plate test in rats, indicating that it has antinociceptive activity. In contrast to (-)-nicotine and (+)-epibatidine, ABT-594 did not cause rotarod impairment at antinociceptive doses but did cause hypothermia and life-threatening adverse effects including seizures. ABT-594 (0.01 and 0.1 mg/kg i.v.) also produced a dose-dependent increase in blood pressure resembling that observed with (-)-nicotine (0.03, 0.1 and 0. 03 mg/kg i.v.) and (+)-epibatidine (0.001 and 0.003 mg/kg i.v.). Both the antinociceptive and toxic effects (convulsions and hypertension) were abolished by pretreatment with the brain penetrant neuronal nAChR antagonist mecamylamine (1 mg/kg s.c.; i.v. for cardiovascular studies), demonstrating that these actions of ABT-594 were mediated via activation of neuronal nicotinic receptors. Continuous infusion of ABT-594 (0.2 mg/kg per day s.c.) to rats for 7 days followed by challenge with mecamylamine (1 mg/kg i.p.) induced a nicotine-like abstinence syndrome suggesting that ABT-594 has nicotine-like dependence liability. These findings indicate that the acute safety profile of ABT-594 is not significantly improved over other nicotinic analgesics.

Outcome of pregnancies complicated by pre-gestational diabetes mellitus

Pregestational diabetes mellitus (DM) is associated with adverse fetal and maternal outcomes. Studies suggest that optimal control of diabetes before and during pregnancy minimises these risks. There are few recent reviews of outcomes of pregnancies complicated by DM in Australia. Ninety-three pregnancies in women with DM at our hospital since 1989 were identified. We collected data for maternal age, type of diabetes, duration of therapy, complications of diabetes, maternal complications of pregnancy and fetal outcomes including malformations. The rate of pregnancy planning with optimal glycaemic control at conception was low in our population, particularly in patients with Type 1 diabetes. Women who smoked had worse glycaemic control, and a higher rate of miscarriage. There was a high rate of Caesarean section, particularly in those women with Type 1 diabetes (77.4%). The rate of Caesarean section was lower in planned pregnancies. There were no perinatal deaths. The number of neonates with major congenital anomalies was high (13%) in the Type 1 population. It is important to increase the rates of prepregnancy planning and to optimise glycaemic control before pregnancy. In many cases there has been a long interval between diagnosis and pregnancy, so all women with diabetes should receive counselling at frequent intervals about pregnancy and the importance of planning. Women who planned their pregnancies had improved outcomes, with decreased rate of Caesarean section, better glycaemic control and better neonatal Apgar scores. Women with diabetes should not smoke during pregnancy because of the increased risk of miscarriage and poorer glycaemic control.

History of the enzyme nomenclature system

Naming things is essential for people to understand one another, no matter what language or field of interest is involved. This is as true for enzymes, genes and chemicals as it is for birds, food, flowers, etc. Effective communication requires a lack of ambiguity, but, in practice, ambiguities abound even between people who use the same language in different parts of the world, or even within the same country. Whereas ambiguities in the words used for common objects or actions have been the basis for many, more-or-less memorable jokes, they can also cause a great deal of confusion. Such linguistic chaos is welcomed by many as being a part of a diverse heritage that should be preserved at all costs to prevent us from descending into Orwellian 'newspeak'. However, in the sciences, there are distinct advantages in others being able to understand what one is doing. Many groups have stressed the need for standardized, universally accepted systems of nomenclature in chemistry, genetics, enzymology, etc. However, it is the universal acceptance that usually causes the problem. It is rare to find people who will admit that they find nomenclature to be an interesting subject, but many who profess contempt for it will get very excited if it is suggested that their pet nomenclature should be changed in the interest of clarity or uniformity. This account will consider the development of the enzyme nomenclature system, its benefits, shortcomings and future prospects.

Possible antimigraine mechanisms of action of the 5HT1F receptor agonist LY334370

This study investigated whether the selective 5HT1F receptor agonist LY334370 has other possible antimigraine mechanisms in addition to the proposed inhibition of dural plasma extravasation. LY334370 (up to 10(-5) M) had no vasoconstrictor effects on human cerebral arteries in vitro. It had no effect (up to 10 mg kg-1, i.v.) on neurogenic vasodilation of dural blood vessels produced by electrical stimulation of the dura mater in anesthetized rats. Nor had it any effect (at 3 mg kg-1, i.v.) on the hyperalgesia produced by injection of carrageenan into the paw of conscious rats or on nociceptive reflex responses in the spinalized, decerebrate rabbit (up to 3 mg kg-1, i.v.), indicating that it has no general analgesic properties. However, it significantly inhibited activation of second-order neurons in the trigeminal nucleus caudalis produced by electrical stimulation of the dura mater in anesthetised rats at 3 mg kg-1, i.v. These results provide evidence to suggest that LY334370 has a central mechanism of action in blocking the transmission of nociceptive impulses within the trigeminal nucleus caudalis and that this may represent a mechanism through which it has its antimigraine effect.

SAR in the alkoxy lactone series: the discovery of DFP, a potent and orally active COX-2 inhibitor

Extensive SAR has been established in the alkoxy lactone series and this has lead to the discovery of DFP (5,5-dimethyl-3-(2-propoxy)-4-methanesulfonylphenyl)-2(5H)-furanon e), a potent COX-2 inhibitor exhibiting in vivo efficacy in all models studied.

Rofecoxib [Vioxx, MK-0966; 4-(4'-methylsulfonylphenyl)-3-phenyl-2-(5H)-furanone]: a potent and orally active cyclooxygenase-2 inhibitor. Pharmacological and biochemical profiles

The discoveries that cyclooxygenase (COX)-2 is an inducible form of COX involved in inflammation and that COX-1 is the major isoform responsible for the production of prostaglandins (PGs) in the gastrointestinal tract have provided a rationale for the development of specific COX-2 inhibitors as a new class of anti-inflammatory agents with improved gastrointestinal tolerability. In the present study, the preclinical pharmacological and biochemical profiles of rofecoxib [Vioxx, also known as MK-0966, 4-(4'-methylsulfonylphenyl)-3-phenyl-2-(5H)-furanone], an orally active COX-2 inhibitor, are described. Rofecoxib is a potent inhibitor of the COX-2-dependent production of PGE(2) in human osteosarcoma cells (IC(50) = 26 +/- 10 nM) and Chinese hamster ovary cells expressing human COX-2 (IC(50) = 18 +/- 7 nM) with a 1000-fold selectivity for the inhibition of COX-2 compared with the inhibition of COX-1 activity (IC(50) > 50 microM in U937 cells and IC(50) > 15 microM in Chinese hamster ovary cells expressing human COX-1). Rofecoxib is a time-dependent inhibitor of purified human recombinant COX-2 (IC(50) = 0.34 microM) but caused inhibition of purified human COX-1 in a non-time-dependent manner that could only be observed at a very low substrate concentration (IC(50) = 26 microM at 0.1 microM arachidonic acid concentration). In an in vitro human whole blood assay, rofecoxib selectively inhibited lipopolysaccharide-induced, COX-2-derived PGE(2) synthesis with an IC(50) value of 0.53 +/- 0.02 microM compared with an IC(50) value of 18.8 +/- 0.9 microM for the inhibition of COX-1-derived thromboxane B(2) synthesis after blood coagulation. Using the ratio of the COX-1 IC(50) values over the COX-2 IC(50) values in the human whole blood assay, selectivity ratios for the inhibition of COX-2 of 36, 6.6, 2, 3, and 0.4 were obtained for rofecoxib, celecoxib, meloxicam, diclofenac, and indomethacin, respectively. In several in vivo rodent models, rofecoxib is a potent inhibitor of carrageenan-induced paw edema (ID(50) = 1.5 mg/kg), carrageenan-induced paw hyperalgesia (ID(50) = 1.0 mg/kg), lipopolysaccharide-induced pyresis (ID(50) = 0.24 mg/kg), and adjuvant-induced arthritis (ID(50) = 0.74 mg/kg/day). Rofecoxib also has a protective effect on adjuvant-induced destruction of cartilage and bone structures in rats. In a (51)Cr excretion assay for detection of gastrointestinal integrity in either rats or squirrel monkeys, rofecoxib has no effect at doses up to 200 mg/kg/day for 5 days. Rofecoxib is a novel COX-2 inhibitor with a biochemical and pharmacological profile clearly distinct from that of current nonsteroidal anti-inflammatory drugs and represents a new therapeutic class of anti-inflammatory agents for the treatment of the symptoms of osteoarthritis and rheumatoid arthritis with improved gastrointestinal tolerability.

The tetrodotoxin-resistant sodium channel SNS has a specialized function in pain pathways

Many damage-sensing neurons express tetrodotoxin (TTX)-resistant voltage-gated sodium channels. Here we examined the role of the sensory-neuron-specific (SNS) TTX-resistant sodium channel alpha subunit in nociception and pain by constructing sns-null mutant mice. These mice expressed only TTX-sensitive sodium currents on step depolarizations from normal resting potentials, showing that all slow TTX-resistant currents are encoded by the sns gene. Null mutants were viable, fertile and apparently normal, although lowered thresholds of electrical activation of C-fibers and increased current densities of TTX-sensitive channels demonstrated compensatory upregulation of TTX-sensitive currents in sensory neurons. Behavioral studies demonstrated a pronounced analgesia to noxious mechanical stimuli, small deficits in noxious thermoreception and delayed development of inflammatory hyperalgesia. These data show that SNS is involved in pain pathways and suggest that blockade of SNS expression or function may produce analgesia without side effects.