Biomedical subjects
Publications and source records attributed to A G Graham.
A series of 2-benzyl-4-sulfonyl-4H-isoquinoline-1,3-diones was prepared. Members of this series are potent and selective inhibitors of cyclooxygenase-2 (COX-2) in both microsomal and cellular assays. Two representatives demonstrated activity in the carrageenan-induced paw edema model in rats upon oral administration.
Meloxicam (5), an NSAID in the enol-carboxamide class, was developed on the basis of its antiinflammatory activity and relative safety in animal models. In subsequent screening in microsomal assays using human COX-1 and COX-2, we discovered that it possessed a selectivity profile for COX-2 superior to piroxicam and other marketed NSAIDs. We therefore embarked on a study of enol-carboxamide type compounds to determine if COX-2 selectivity and potency could be dramatically improved by structural modification. Substitution at the 6- and 7-positions of the 4-oxo-1,2-benzothiazine-3-carboxamide, alteration of the N-methyl substituent, and amide modification were all examined. In addition we explored several related systems including the isomeric 3-oxo-1,2-benzothiazine-4-carboxamides, thienothiazines, indolothizines, benzothienothiazines, naphthothiazines, and 1,3- and 1,4-dioxoisoquinolines. While a few examples were found with greater potency in the COX-2 assay, no compound tested had a better COX-2/COX-1 selectivity profile than that of 5.
BIRM 270 was developed as a potent and enantioselective inhibitor of LTB4 biosynthesis by human neutrophils, and was also found to inhibit LTC4 production by human eosinophils and lung mast cells. BIRM 270 inhibited LTB4 synthesis in neutrophils by preventing arachidonate release from membrane phospholipids, and over the same concentration range, inhibited PAF biosynthesis. BIRM 270 did not directly inhibit acylhydrolases which have been implicated in eicosanoid and PAF biosynthesis, suggesting an indirect mode of action.
A series of benzoxazolamine and benzothiazolamine analogs that inhibit leukotriene (LT) biosynthesis are described. The initial lead, (S)-N-(benzothiazol-2- yl)phenylalanine ethyl ester (5a), was discovered in a screening program for inhibition of Ca-ionophore-A23187-induced LTB4 release in human polymorphonuclear leukocytes (IC50 0.23 microM). Through structural modification, it was determined that hydrophobic substituents in the 5-position and replacement of the phenyl ring of phenylalanine with a cyclohexyl group greatly enhance potency. Several ester bioisosteres that retain potency and enantiomeric selectivity are described. Lead optimization culminated in (S)-N-[2-cyclohexyl-1-(2-pyridinyl)ethyl]-5-methyl-2-benzoxazolamine+ ++ (43b), IC50 0.001 microM. The compounds described are not inhibitors of 5-lipoxygenase but, rather, act at the level of arachidonic acid release.
(S)-N-[2-Cyclohexyl-1-(2-pyridinyl)ethyl]-5-methyl-2-benzoxazolamine+ ++ (BIRM 270) was identified as a potent and enantiomerically selective inhibitor of calcium ionophore A23187-stimulated leukotriene B4 biosynthesis in human neutrophils. The (S)- and (R)-enantiomers exhibited IC50 values of 1 nM and 40 nM, respectively. BIRM 270 did not inhibit 5-lipoxygenase activity in a cell-free assay. In addition, the compound did not interfere with the conversion of exogenous 5-lipoxygenase substrate (15S)-hydroperoxyeicosatetraenoic acid to (5S, 15S)-dihydroxyeicosatetraenoic acid in intact, ionophore-stimulated neutrophils. Under the same experimental conditions, BIRM 270 inhibited the production of 5-lipoxygenase products from endogenous substrate, suggesting that the compound affected arachidonate availability rather than metabolism. Consistent with this concept, the inhibition of leukotriene B4 biosynthesis by BIRM 270 was overcome by the addition of exogenous arachidonic acid to the leukocyte preparation. Direct measurement of free arachidonate by gas chromatography-mass spectrometry confirmed that BIRM 270 inhibited arachidonate release from ionophore-stimulated neutrophils. The compound did not affect arachidonate reacylation. The blockage of arachidonate release coincided with inhibition of leukotriene B4 biosynthesis in these cells. BIRM 270 also inhibited ionophore-stimulated platelet-activating factor biosynthesis by human neutrophils. Although these results suggest that BIRM 270 inhibited phospholipase A2-mediated deacylation of membrane phospholipids, the compound did not directly inhibit the high molecular weight, cytosolic phospholipase A2 derived from human neutrophils or U937 cells. Thus, suppression of arachidonate mobilization by BIRM 270 may be due to indirect inhibition of intracellular phospholipase A2 or to inhibition of another acylhydrolase activity.
BACKGROUND: The action of 5-lipoxygenase on arachidonic acid generates potent inflammatory mediators that may contribute to the pathophysiology of asthma. METHODS: Using the potent and selective 5-lipoxygenase inhibitor BI-L-239, we have examined the role of 5-lipoxygenase products in three animal models of asthma. RESULTS: In vitro BI-L-239 inhibited 5-lipoxygenase product generation from human lung mast cells, alveolar macrophages, and peripheral blood leukocytes with a concentration that would provide 50% inhibition values of 28 to 340 nmol/L. A 36-fold selectivity for immunoreactive leukotriene C4 versus immunoreactive prostaglandin D2 inhibition was demonstrated in mast cells. In anesthetized cynomolgus monkeys, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced immunoreactive leukotriene C4 release (maximum, 73%; bronchoalveolar lavage [BAL], 20 minutes), late-phase bronchoconstriction (maximum, 41%; +6 to 8 hours), and neutrophil infiltration (maximum, 63%; BAL, +8 hours). In conscious sheep, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced late-phase bronchoconstriction (maximum, 66%; +6 to 8 hours) and increase in airway responsiveness (maximum, 82%; carbachol, +24 hours). The acute bronchoconstriction was shortened, and neutrophil infiltration diminished (maximum, 61%; BAL, +8 hours) in this model. Finally in conscious actively sensitized guinea pigs pretreated with pyrilamine and indomethacin, inhaled BI-L-239 attenuated acute bronchoconstriction (maximum, 80%; +5 to 15 minutes), leukocyte infiltration (58%; BAL, +3 days) and increase in airway responsiveness (100%; methacholine, +3 days) induced by three alternate-day ovalbumin inhalations. CONCLUSIONS: In conclusion, results in these three animal models indicate that 5-lipoxygenase products may be major contributors to the bronchoconstriction (especially late phase), leukocyte infiltration, and airway hyperresponsiveness that characterize asthma.
BI-L-226, a 2,6-disubstituted 4-(2-arylethenyl)phenol, is a potent and selective 5-lipoxygenase inhibitor which shows excellent inhibition of antigen-induced leukotriene generation in the lung of cynomolgus monkeys by aerosol administration, although little activity has been observed by the p.o. route. The facile synthesis of the succinate ester BI-L-357, however, results in a prodrug which has p.o. activity between 10 to 30 mg/kg in an ex vivo whole blood model of leukotriene B4 generation in both squirrel and cynomolgus monkeys. In addition, the prodrug is effective in inhibiting pulmonary leukotriene C4 production in antigen-challenged cynomolgus monkeys in the same dose range. Plasma levels of the parent compound in the monkey after p.o. administration of 30 mg/kg are 25-fold higher than the IC50 needed for in vitro inhibition of leukotriene B4 in whole blood. Absolute bioavailability of the parent compound was 50%. The prodrug concept therefore extends the potential of this class of compounds to inflammation sites mediated by 5-lipoxygenase not readily treated by topical administration.
A series of 2,6-disubstituted 4-(2-arylethenyl)phenols with potent human neutrophil 5-lipoxygenase (5-LO) inhibiting activity (IC50S in the 10(-7) M range) and weaker human platelet cyclooxygenase (CO) inhibiting activity (IC50S in the 10(-6) M range) is described. This series evolved from the chemical modification of an antiinflammatory dual CO/5-LO inhibitor, 2,6-di-tert-butyl-4-[2-(3-pyridyl)ethenyl]phenol (BI-L-93 BS). The potency and selectivity for 5-LO inhibition is greatly influenced by the nature of the substituents in the 2- and 6-positions. Other structure-activity relationships that determine relative 5-LO and CO potency are discussed. In vivo activity against antigen-induced leukotriene-mediated bronchoconstriction and cell influx in guinea pigs is presented. Representatives of the series are active when administered at 30 mg/kg ip.
A series of 2,6-di-tert-butyl-4-(2-arylethenyl)phenols was prepared and examined for their ability to inhibit cyclooxygenase and 5-lipoxygenase in vitro and developing adjuvant arthritis in vivo in the rat. Structure-activity relationships are discussed. Among the best compounds is (E)-2,6-di-tert-butyl-4-[2-(3-pyridinyl)ethenyl]phenol (7d). It has an IC50 of 0.67 microM for cyclooxygenase and 2.7 microM for 5-lipoxygenase and an ED50 of 2.1 mg/kg in developing adjuvant arthritis. Additional in vivo data are reported for 7d.
We present a retrospective 10 year analysis of 76 patients with urothelial tumours of the upper urinary tract. Patients older than 65 years, and female patients, presented with more advanced stages and had a worse prognosis. The grade and stage of the tumour has the greatest impact on survival. No conclusions can be drawn on the efficacy of various types of surgery, but simple nephrectomy gave a 5-year survival of 68%, with a stump recurrence rate of 15%. We observed that patients with urothelial tumours had 4 fold increased chance of developing gastrointestinal cancer.
A retrospective analysis of the blood groups of 74 patients with transitional cell carcinoma of the upper urinary tract is presented. The blood group distribution of the patients reflected that of the general population. No relationship was found between blood groups and stage and grade of the tumour or patient survival. Nor were blood groups predictive of bladder tumour recurrence and stump recurrence in patients who had undergone simple nephrectomy.
Eighty-six hypertensive patients with arteriographic evidence of renal artery stenosis presented between 1968 and 1979. Thirty-nine subsequently underwent surgery and were followed thereafter for at least one year. In 54 per cent blood pressure was reduced to within one standard deviation of the mean for a normal individual of the same sex and age. A further thirty-one per cent of patients were 'improved', but needed hypotensive drugs to maintain blood pressure within this range. In the remaining 15 per cent of patients the operation did not reduce blood pressure. The purpose of the study was to assess our ability to predict this varies surgical outcome using clinical observations and special tests. The latter included measurement of plasma renin concentration in both peripheral vein and renal vein plasma, catheterization of both ureters and studies of the response of blood pressure to brief infusion of saralasin. No single observation or test, no combination of observations or tests and no discriminant function clearly separated patients in whom surgery would succeed from those in whom it would fail. Renal vein renin ratio was the best test; all patients with a ratio greater than 2.0 underwent successful surgery, but so too did some patients with a lower ratio. We also analysed the factors which had influenced our decision to undertake special investigations in 65 of the 86 patients and, having done these investigations, to recommend surgery in 39. No single factor seemed to have had overriding importance in making these decisions.
Recent reports have been critical of the long-term results of ileal and colonic conduit diversion of urine in children, indicating a major complication rate of over 50%. The writer has therefore reviewed 26 consecutive personal cases, followed up for 6 to 20 years. Only 3 (12%) have had major problems, none related to the stoma, and possible reasons for the low complication rate are discussed. It is concluded that it is premature to condemn ileal conduit diversion of urine in children, when properly indicated, provided care in technique and follow-up is observed.
We studied 23 patients with suspected renal hypertension, including 12 with renal artery stenosis, or occlusion. Total effective renal plasma flow (ERPF) was measured in all patients by conventional p-aminohippurate (PAH) clearance and by 123I-hippuran clearance performed on the same day. A close correlation between the two techniques was obtained (r = 0.87, P less than 0.001) with the latter technique underestimating the former by a mean ratio of 0.89:1.00. We describe a technique for deriving ERPF for individual kidneys by 123I-hippuran renography, and the data obtained by this method correlate well with data obtained from bilateral ureteric catheterization studies (r = 0.076, P less than 0.001 for both affected and unaffected sides) in 17 patients. The renographic technique is particularly accurate in quantitating ERPF in the 12 patients with renal artery stenosis, and is recommended as the investigation of choice in the assessment of ERPF in patients with this condition.
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A review of all prostatectomies performed by urologists in Scotland during 1969-1974 is presented. Factors influencing the mortality rate are discussed and the steady increase in low-mortality (1.4%) transurethral prostatectomy noted.
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The ultrasonic features of 162 bladder tumours are described. Comparing clinical staging by the TNM system and the ultrasonic appearances, there is a high degree of accuracy in staging by ultrasound. The use of this painless non-invasive technique is assessed and should be used in staging bladder tumours only in conjunction with other established methods, and not in isolation.