Clinical trial: levofloxacin-based quadruple therapy was inferior to traditional quadruple therapy in the treatment of resistant Helicobacter pylori infection

BACKGROUND

The efficacy of levofloxacin-based quadruple therapy in resistant Helicobacter pylori infection is not known.

AIM

To test the efficacy of levofloxacin-based quadruple therapy and traditional quadruple therapy in resistant H. pylori infection.

METHODS

One hundred and two patients with resistant H. pylori infection were randomized to 1 week of either EBAL (esomeprazole 40 mg b.d., bismuth subcitrate 240 mg b.d., amoxicillin 1 g b.d. and levofloxacin 500 mg b.d.) or EBMT (esomeprazole 40 mg b.d., bismuth subcitrate 240 mg b.d., metronidazole 400 mg t.d.s. and tetracycline 500 mg q.d.s.). (13)C-urea breath test was performed at week 12 to assess post-treatment H. pylori status.

RESULTS

In intention-to-treat analysis H. pylori eradication was achieved in 37 of 51 (73%) subjects in EBAL and 45 of 51 (88%) subjects in EBMT groups, respectively (P = 0.046). Per-protocol eradication rates of EBAL and EMBT groups were 78% and 94%, respectively (P = 0.030). The intention-to-treat eradication rate was statistically lower for EBAL than EMBT (56% vs. 90%, P = 0.013) among those who had failed more than one course of eradication therapy. Previous levofloxacin triple therapy did not affect the efficacy of either protocol significantly.

CONCLUSIONS

Levofloxacin-based quadruple therapy was inferior to traditional quadruple therapy for resistant H. pylori infection.

Lansoprazole, levofloxacin and amoxicillin triple therapy vs. quadruple therapy as second-line treatment of resistant Helicobacter pylori infection

AIM

To test the efficacy of levofloxacin-based second-line therapy for resistant Helicobacter pylori infection.

METHODS

One hundred and six patients who failed H. pylori eradication were randomized to receive (i) lansoprazole 30 mg, amoxicillin 1 g, levofloxacin 500 mg, all given twice daily for 7 days (LAL); or (ii) lansoprazole 30 mg twice daily, metronidazole 400 mg thrice daily, bismuth subcitrate 120 mg and tetracycline 500 mg four times daily for 7 days (quadruple). Post-treatment H. pylori status was determined by (13)C-urea breath test.

RESULTS

Intention-to-treat and per-protocol H. pylori eradication rates were 57/60% for the LAL group and 71/76% for the quadruple group respectively. Metronidazole, clarithromycin, amoxicillin and levofloxacin resistance were found in 76%, 71%, 0% and 18% of patients, respectively. Levofloxacin resistance led to treatment failure in the LAL group. For patients with dual resistance to metronidazole and clarithromycin, the eradication rates were 79% in the LAL group (levofloxacin-sensitive) and 65% in the quadruple group (P=0.34).

CONCLUSION

Lansoprazole, amoxicillin plus levofloxacin second-line therapy is comparable with quadruple therapy in efficacy. Subjects, especially those with dual resistance to metronidazole and clarithromycin, may consider levofloxacin-based therapy for levofloxacin-sensitive strains.

Randomized controlled study of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy as second-line treatment for Helicobacter pylori infection

AIM

To test the efficacy of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy for the second-line treatment of Helicobacter pylori infection.

METHODS

One hundred and nine patients who had failed previous H. pylori eradication were randomized to receive: (i) rabeprazole, 20 mg b.d., rifabutin, 300 mg once daily, and levofloxacin, 500 mg once daily, for 7 days (triple therapy); or (ii) rabeprazole, 20 mg b.d., metronidazole, 400 mg t.d.s., bismuth subcitrate, 120 mg q.d.s., and tetracycline, 500 mg q.d.s., for 7 days (quadruple therapy). Endoscopy and culture were performed before treatment.

RESULTS

The clarithromycin (79% vs. 21%, P < 0.001) and metronidazole (89% vs. 40%, P < 0.001) resistance rates were significantly higher in patients with previous exposure than in those with no previous exposure. The intention-to-treat and per protocol eradication rates were 91%/91% for the triple therapy group and 91%/92% for the quadruple therapy group. For patients with double resistance to metronidazole and clarithromycin, the eradication rates were 85% (17/20) in the triple therapy group and 87% (13/15) in the quadruple therapy group. Compliance was greater than 95% for both regimens.

CONCLUSION

Rabeprazole, levofloxacin and rifabutin-based triple therapy and quadruple therapy were equally effective as second-line treatments for H. pylori infection.

Efficacy of enzyme immunoassay for the detection of Helicobacter pylori antigens in frozen stool specimens: local validation

AIM

To investigate the efficacy of measurement of Helicobacter pylori stool antigen (HpSA) using stored frozen stool specimens, and to assess whether there were factors affecting efficacy in Hong Kong.

METHODS

Patients undergoing upper endoscopy at Tuen Mun Hospital were recruited. Stool samples were saved for HpSA testing and questionnaires were completed. Stool samples were frozen immediately upon receipt and stored at -70 degrees C until tested. HpSA results were compared with rapid urease test and histology.

RESULTS

One hundred and eighty-one patients were recruited. One hundred and seventy-eight patients were suitable for analysis. Eighty-three were H. pylori positive and 95 were H. pylori negative. The mean duration of storage of the stool samples was 120 days (range, 40-225 days). The sensitivity, specificity and positive and negative predictive values were 84.3%, 97.9%, 97.2% and 88.6%, respectively. In patients with a false negative HpSA test, there was a significant delay in collecting the stool specimen after endoscopy when compared with those with a true positive HpSA test (4.2 vs. 2.3 days; P < 0.05). However, the duration of storage of the specimens was not longer, and consumption of coffee or tea and smoking habits were similar.

CONCLUSIONS

HpSA testing showed good sensitivity and specificity, even with frozen stool samples stored for up to 225 days. The efficacy was not affected by coffee, tea or smoking.

Double blind, randomised, placebo controlled study of four weeks of lansoprazole for the treatment of functional dyspepsia in Chinese patients

BACKGROUND

The use of proton pump inhibitors for the treatment of functional dyspepsia is controversial and the role of Helicobacter pylori infection in functional dyspepsia is uncertain.

AIM

To evaluate the efficacy of different doses of lansoprazole for the treatment of functional dyspepsia in Chinese patients.

METHOD

Patients with a clinical diagnosis of functional dyspepsia according to the Rome II criteria and normal upper gastrointestinal endoscopy were recruited and randomised to receive: (1) lansoprazole 30 mg, (2) lansoprazole 15 mg, or (3) placebo, all given daily for four weeks. Dyspepsia symptom scores and quality of life (SF-36 score) were evaluated before and four weeks after treatment.

RESULTS

A total of 453 patients were randomised. There was no difference in the proportion of patients with complete symptom relief in the lansoprazole 30 mg (23%) and lansoprazole 15 mg (23%) groups compared with the placebo group (30%). The proportion of H pylori positive patients with a complete response was similar with lansoprazole 30 mg (34%) and lansoprazole 15 mg (20%) versus placebo (22%). All symptom subgroups (ulcer-like, dysmotility-like, reflux-like, and unspecified dyspepsia) had similar proportions of patients with complete symptom relief after treatment.

CONCLUSION

Proton pump inhibitor treatment is not superior to placebo for the management of functional dyspepsia in Chinese patients.

Rabeprazole-based 3-day and 7-day triple therapy vs. omeprazole-based 7-day triple therapy for the treatment of Helicobacter pylori infection

BACKGROUND

Rabeprazole is a new proton pump inhibitor with more potent acid suppressive and anti-Helicobacter effects.

AIM

To compare two different regimens of rabeprazole-based triple therapy vs. 7-day omeprazole-based triple therapy for the eradication of Helicobacter pylori infection.

METHOD

Patients with proven H. pylori infection were randomized to receive: (i) 7-day rabeprazole, 10 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg, all twice daily; (ii) 3-day rabeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg, all twice daily; or (iii) 7-day omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg, all twice daily. Endoscopy (CLO test, histology) was performed before randomization and 6 weeks after drug treatment.

RESULTS

One hundred and seventy-three patients were randomized. H. pylori eradication rates (intention-to-treat, n=173/per protocol, n=167) were 88%/91% for 7-day rabeprazole-based therapy, 72%/72% for 3-day rabeprazole-based therapy and 82%/89% for 7-day omeprazole-based therapy, respectively. The per protocol eradication rate was significantly better in the 7-day rabeprazole-based therapy and 7-day omeprazole-based therapy groups when compared to the 3-day rabeprazole-based therapy group (P=0.01 and P=0.04, respectively). Compliance was excellent and all three regimens were well tolerated.

CONCLUSIONS

The efficacy of seven-day rabeprazole-based triple therapy is similar to 7-day omeprazole-based triple therapy for the eradication of H. pylori infection.

Evaluation of five commercial serological tests for the detection of Helicobacter pylori infection in Chinese

BACKGROUND

Commercial serological tests for the detection of Helicobacter pylori infection must be locally validated. We evaluated the accuracy of five commercial tests in the Chinese population.

METHODS

Serum samples were collected from patients referred for upper endoscopy. Antral biopsies were taken for histological examination and culture of H. pylori. The gold standard for diagnosing H. pylori infection was positive histological staining and/or positive H. pylori culture. The serum samples were tested for H. pylori antibodies using the following tests: (i) Cobas Core Anti-H. pylori EIA; (ii) GAP IgG; (iii) GAP IgM; (iv) H. pylori microwell EIA (Quidel); and (v) Premier H. pylori. The sensitivity, specificity and accuracy of each test was calculated according to the manufacturers' instructions or according to a new cut-off value.

RESULTS

A total of 158 patients were recruited amongst whom 114 (72%) were H. pylori-positive. Indeterminate results varied from 7% to 19%. The accuracy of the tests varied from 57% to 85%. By using new cut-off values, the accuracy was much improved, ranging from 73.4% to 86.7%.

CONCLUSIONS

By defining new cut-off values for the Chinese population, we were able to improve the performance of some of the serology tests. This illustrates the importance of local validation.

Anti-Helicobacter pylori activity of Chinese tea: in vitro study

BACKGROUND

Chinese tea has an antibacterial activity against a wide range of bacteria. However, its activity against Helicobacter pylori has not been reported.

METHOD

In this study the anti-Helicobacter pylori effects of a Chinese tea (Lung Chen tea), and two tea catechins, epigallocatechin gallate and epicatechin and their minimum inhibitory concentrations (MICs) were examined. The effect of Lung Chen on metronidazole resistance was also studied using the E-test.

RESULTS

Lung Chen, epigallocatechin gallate and epicatechin all inhibited the growth of H. pylori. The MIC90 for Lung Chen was 0. 25-0.5% (w/w) and that of epigallocatechin gallate and epicatechin were 50-100 and 800-1600 microg/mL, respectively. Epigallocatechin gallate is probably the active ingredient responsible for most of the anti-H. pylori activity of Chinese tea. Lung Chen did not reverse metronidazole resistance.

CONCLUSIONS

Chinese tea has anti-H. pylori activity in a daily consumed concentration, and epigallocatechin gallate is probably the active ingredient responsible for the action.

1,2-Dibenzamidobenzene inhibitors of human factor Xa

High-throughput screening of a combinatorial library of diamidophenols yielded lead compounds with the ability to inhibit human factor Xa (fXa) at micromolar concentrations (e.g. compound 4, fXa apparent K(ass) = 0.64 x 10(6) L/mol). SAR studies in this novel structural series of fXa inhibitors showed that the phenolic hydroxyl group was not essential for activity. The best activity was found in substituted 1,2-dibenzamidobenzenes in which the phenyl group of one benzoyl group (A-ring) was substituted in the 4-position with relatively small lipophilic or polarizable groups such as methoxy, vinyl, or chloro and the phenyl group of the other benzoyl group (B-ring) was substituted in the 4-position with larger lipophilic groups such as tert-butyl or dimethylamino. The central phenyl ring (C-ring) tolerated a wide variety of substituents, but methoxy, methanesulfonamido, hydroxyl, and carboxyl substitution produced slightly higher levels of activity than other substituents when present in combination with favorable B-ring substitution. Methylation of the amide nitrogen atoms was found to greatly decrease activity. Compound 12 is the highest affinity fXa inhibitor in this group of compounds, having fXa apparent K(ass) = 25.5 x 10(6) L/mol, about 40x more active than the original lead. This lead series does not show potent inhibition of human thrombin. A model for the binding of these ligands to the fXa active site is proposed. The model is consistent with the observed SAR and can serve to guide future SAR studies.

N(2)-Aroylanthranilamide inhibitors of human factor Xa

Reversal of the A-ring amide link in 1,2-dibenzamidobenzene 1 (fXa K(ass) = 0.81 x 10(6) L/mol) led to a series of human factor Xa (hfXa) inhibitors based on N(2)-aroylanthranilamide 4. Expansion of the SAR around 4 showed that only small planar substituents could be accommodated in the A-ring for binding to the S1 site of hfXa. Bulky groups such as 4-isopropyl, 4-tert-butyl, and 4-dimethylamino were favored in the B-ring to interact with the S4 site of hfXa. The central (C) ring containing a 5-methanesulfonamido group yielded greater activity than carbamoyl groups. Combining the beneficial features from the B- and C-ring SAR, compound 55 represents the most potent hfXa inhibitor in the N(2)-aroylanthranilamide 4 series with hfXa K(ass) = 58 x 10(6) L/mol (K(i) = 11.5 nM).

Strongyloidiasis as a possible cause of nephrotic syndrome

Chronic strongyloidiasis is a mild disease and has never been reported to be associated with nephrotic syndrome. Disseminated strongyloidiasis is known to have high mortality, but it frequently is not diagnosed until autopsy. We report a patient with nephrotic syndrome developing disseminated strongyloidiasis after steroid therapy. The findings in renal biopsy, the time course of the development, and resolution of nephrotic syndrome after thiabendazole treatment suggested a possible causal relationship between chronic strongyloidiasis and nephrotic syndrome. The case also demonstrated the importance of early diagnosis in disseminated strongyloidiasis and the good clinical outcome of early treatment before the development of organ failure.

Ulcerative colitis exacerbation associated with cytomegalovirus infection

There is an increasing prevalence of ulcerative colitis in Hong Kong and cytomegalovirus infection is an important factor in the exacerbation of the disease. We report on a 33- year-old Chinese man with ulcerative colitis in remission, who presented with bloody diarrhoea that failed to respond to an intensive regimen of oral and rectal steroid. Colonoscopy was performed and biopsy specimens showed signs of cytomegalic colitis in association with ulcerative colitis. Administration of ganciclovir and the gradual termination of steroid treatment resulted in remission of the colitis. The clinical course suggested an exacerbation of ulcerative colitis due to cytomegalovirus infection. The relationship between ulcerative colitis and cytomegalovirus is discussed.

Identification of essential residues for the catalytic function of 85-kDa cytosolic phospholipase A2. Probing the role of histidine, aspartic acid, cysteine, and arginine

Cytosolic phospholipase A2 (cPLA2) hydrolyzes the sn-2-acyl ester bond of phospholipids and shows a preference for arachidonic acid-containing substrates. We found previously that Ser-228 is essential for enzyme activity and is likely to function as a nucleophile in the catalytic center of the enzyme (Sharp, J. D., White, D. L., Chiou, X. G., Goodson, T., Gamboa, G. C., McClure, D., Burgett, S., Hoskins, J., Skatrud, P. L., Sportsman, J. R., Becker, G. W., Kang, L. H., Roberts, E. F., and Kramer, R. M.(1991) J. Biol. Chem. 266, 14850-14853). cPLA2 contains a catalytic aspartic acid motif common to the subtilisin family of serine proteases. Substitution within this motif of Ala for Asp-549 completely inactivated the enzyme, and substitutions with either glutamic acid or asparagine reduced activity 2000- and 300-fold, respectively. Additionally, using mutants with cysteine replaced by alanine, we found that Cys-331 is responsible for the enzyme's sensitivity to N-ethylmaleimide. Surprisingly, substituting alanine for any of the 19 histidines did not produce inactive enzyme, demonstrating that a classical serine-histidine-aspartate mechanism does not operate in this hydrolase. We found that substituting alanine or histidine for Arg-200 did produce inactive enzyme, while substituting lysine reduced activity 200-fold. Results obtained with the lysine mutant (R200K) and a coumarin ester substrate suggest no specific interaction between Arg-200 and the phosphoryl group of the phospholipid substrate. Arg-200, Ser-228, and Asp-549 are conserved in cPLA2 from six species and also in four nonmammalian phospholipase B enzymes. Our results, supported by circular dichroism, provide evidence that Asp-549 and Arg-200 are critical to the enzyme's function and suggest that the cPLA2 catalytic center is novel.

A novel series of selective leukotriene antagonists: exploration and optimization of the acidic region in 1,6-disubstituted indoles and indazoles

A systematic structure-activity exploration of the carboxylic acid region in a series of indole- or indazole-derived leukotriene antagonists 1 led to several discoveries. Use of the 3-methoxy-p-tolyl fragment (illustrated in acid 1) for connecting the indole and the acidic site provides the most potent carboxylic acids 1, tetrazoles 20, and aryl sulfonimides 21. The aryl sulfonimides are 5-500 times more potent (in vitro and/or in vivo) than the corresponding carboxylic acids 1. The o-tolyl sulfonimides such as 114 show greater oral potency than the phenyl sulfonimides at a given level of in vitro activity. Acidic keto sulfone derivatives 10 (Nu = CH-(CO2CH3)SO2Ph) mimic the activity of the sulfonimides.

Synthesis and in vitro LTD4 antagonist activity of bicyclic and monocyclic cyclopentylurethane and cyclopentylacetamide N-arylsulfonyl amides

The dissociation constants (KB) at the LTD4 receptor on guinea pig trachea of a series of monocyclic and bicyclic cyclopentylurethane and cyclopentylacetamide N-arylsulfonyl amides have been measured. The KB was found to be remarkably tolerant of changes in the electronic constitution and lipophilicity of the bicyclic ring system (template). Thus, N-[4[[6-[[(cyclopentyloxy)carbonyl]amino]benzimidazol-1- yl]methyl]-3-methoxybenzoyl]benzenesulfonamide (11a) and N-[4-[[5-[[(cyclopentyloxy)carbonyl]amino]benzo[b]thien-3- yl]methyl]-3-methoxybenzoyl]benzene-sulfonamide (25a) had closely similar affinities (pKB, 9.20 and 9.31, respectively; LTE4 as agonist). It has been shown that the hetero-ring of the template need not be aromatic in order to achieve high affinity, since indoline 31 and 2,3-dihydrobenz-1,4-oxazines 37a-c had pKBs greater than 9. Further, it has been shown that an o-aminophenone (see 42 and Figure 3) can function as a template; the template in 42 [see iii] is bicyclic by virtue of the presence of an intramolecular hydrogen bond. In contrast, when the template is a phenyl ring (48), receptor affinity is markedly reduced. These findings support the notion that central bicyclic ring system in this family of peptidoleukotriene antagonists is a molecular feature which helps to preorganize the acylamino and acidic chains and thereby facilitate the molecular recognition event.

Evolution of a series of peptidoleukotriene antagonists: synthesis and structure-activity relationships of 1,6-disubstituted indoles and indazoles

A perception of structural similarities between two independent series of leukotriene antagonists (one emanating from FPL 55712 and one based upon the leukotrienes themselves) led to the discovery of a novel class of indole and indazole derived antagonists of peptidoleukotrienes. A systematic exploration of C-6 substituted 4-(indol-1-ylmethyl)-3-methoxybenzoic acids identified cyclopentylacetamide and cyclopentylurethane as preferred substituents. The corresponding indazoles were equipotent. These compounds are selective leukotriene antagonists with pKB values of 7.5-7.8 vs LTE4 on guinea pig trachea.

The preclinical pharmacology of ICI 204,219. A peptide leukotriene antagonist

ICI 204,219 (4-(5-cyclopentyloxycarbonylamino-1-methylindol-3-ylmethy l)-3- methoxy-N-o-tolylsulfonylbenzamide) was designed as a peptide leukotriene (LT) antagonist. The compound is a competitive antagonist of LTD4- and LTE4-induced contraction of guinea pig lung tracheal and parenchymal strips with an apparent negative log molar dissociation constant (KB) of approximately 9.6. ICI 204,219 did not antagonize LTC4-induced contractions of guinea pig trachea when the metabolism of LTC4 to LTD4 and, subsequently, to LTE4 was inhibited. The compound inhibited the binding of [3H]LTD4, [3H]LTE4, and [3H]ICI 198,615 (a potent LT antagonist from a different heterocyclic series) to guinea pig lung parenchymal membranes in a competitive manner, and also inhibited [3H]ICI 198,615 binding to human lung parenchymal membranes. ICI 204,219 did not bind to a variety of other receptors when evaluated at concentrations 1,000- to 10,000-fold higher than the apparent KB value for peptide LT receptors. When administered orally, intravenously, or by aerosol, the compound provided dose-related antagonism of the airway effects of aerosol LTD4 in conscious guinea pigs. ED50 values and pharmacodynamic t1/2 (min) for oral, intravenous and aerosol routes of administration were, respectively: 0.52 mumol/kg, greater than 816 min; 0.046 mumol/kg, 85 min; 5.1 x 10(-6) M, 109 min. ICI 204,219 also produced dose-related inhibition of the effects of LTC4 (aerosol or intravenous administration) on pulmonary mechanics in anesthetized guinea pigs when administered orally, intraduodenally, intravenously, or by aerosol. The compound also reversed bronchospasm produced by LTs. Aerosol ovalbumin antigen-induced bronchospasm in guinea pigs was both inhibited and reversed by ICI 204,219. Lastly, the compound inhibited LTD4-induced increases in cutaneous vascular permeability in guinea pigs, being 1,006- and 679-fold more potent than the first generation LT antagonists LY 171,883 and FPL 55712, respectively. ICI 204,219 is a potent, selective, orally active LT antagonist currently undergoing clinical trials.

Hydroxyacetophenone-derived antagonists of the peptidoleukotrienes

Considerations of the possible similarities between leukotriene D4 and its prototypical antagonist, FPL 55712, led to the development of a new series of leukotriene antagonists incorporating a hydroxyacetophenone group (e.g., the toluic acids 16 and 18). Although considerable attention has focused on FPL 55712-derived analogues, only limited investigations into alternatives for the standard 4-acetyl-3-hydroxy-2-propylphenoxy moiety have been reported. Therefore, an extensive study of modifications to the hydroxyacetophenone portion of toluic acid 18 was undertaken. Although no viable alternative to the 3-hydroxy moiety was discovered, replacements for the 2-propyl group (34, 37) and the 4-acetyl functionality (56, 59) yielded potent antagonists. A number of compounds exhibited longer duration of action in vivo than FPL 55712.

In vitro pharmacology of ICI 198,615: a novel, potent and selective peptide leukotriene antagonist

ICI 198,615 is a representative compound from a new class of peptide leukotriene (LT) receptor antagonists. In isolated guinea pig trachea and parenchymal lung strips, ICI 198,615 demonstrated competitive antagonism of the contractile activity of LTD4 and LTE4 with pA2 values of 10.1 to 9.5, respectively. The compound also appeared to antagonize the contractile activity of LTC4 in guinea pig trachea; however, in the presence of an inhibitor of the metabolism of LTC4 to LTD4, ICI 198, 615 provided a pKB value of 5.3, indicating weak antagonism at the LTC4 receptor. ICI 198,615 was also a potent antagonist of LTC4 and LTD4 in isolated human bronchi and pulmonary veins with pKa values of 9.75 +/- 0.32 to 9.20 +/- 0.24, respectively. When evaluated for activity on a broad variety of non-LT receptors, the compound displayed a minimal selectivity of 6310 and a maximal selectivity of greater than 125,000 for the LTE4 receptor. These in vitro studies indicate that ICI 198,615 is the most potent and selective peptide LT receptor antagonist described to date.

In vivo pharmacology of ICI 198,615: a novel, potent and selective peptide leukotriene antagonist

The in vivo pharmacology of ICI 198,615, a highly potent and selective peptide leukotriene (LT) receptor antagonist, is described. In a conscious guinea pig model, ICI 198,615 provided dose-related antagonism of aerosol LTD4-induced dyspnea when administered p.o., i.v. or by aerosol. The pharmacologic half-lives of ICI 198,615 by these routes of administration were greater than 16 hr, 68 min and 34 min, respectively. In pulmonary mechanics studies in which the effects of i.v. or aerosol administration of LTC4 and LTD4 on pulmonary resistance (Rp) or dynamic lung compliance (Cdyn) could be quantitated, ICI 198,615 provided dose-related antagonism when administered p.o., i.d, i.v. or by aerosol. The compound also antagonized LTE4-induced changes in Rp and Cdyn when administered i.v. ICI 198,615 reversed the effect of LTC4, LTD4 and LTE4 on Rp, as well as the effect of LTC4 and LTE4 on Cdyn. The compound was less able to reverse the effect of LTD4 on Cdyn. These results indicate that ICI 198,615 possesses an in vivo profile which is consonant with utility in the treatment of allergic diseases.