Antiinflammatory,analgesic, and antipyretic activities of methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl-2H-pyrazolo[3,4-d]pyrimidine-2-carboxylate (AA-2379), a novel non-acidic agent

The antiinflammatory, analgesic, and antipyretic activities of methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl-2H-pyrazolo[3,4-d] pyrimidine-2-carboxylate (AA-2379), a novel nonacidic agent, were examined.

1. AA-2379 had a potent antiinflammatory activity; 3–25 mg/kg, p.o. of the compound inhibited rat carrageenin-, bradykinin-, trypsin-, formalin-, dextran-, and nystatin-induced paw edema; mouse traumatic edema; and rat croton oil pouch inflammation by about 30%. The compound at 25–50 mg/kg, p.o. also inhibited the vascular permeability induced by histamine, serotonin, and bradykinin.
2. AA-2379 had an analgesic activity; the ID₅₀ values in mouse phenylquinone-induced writhing were 10.1 mg/kg, p.o. and the compound at 12.5 mg/kg, p.o. inhibited dog urate arthritis.
3. AA-2379 at 3–10 mg/kg, p.o. showed antipyretic activity in febrile rats and rabbits.
4. AA-2379, at 500 mg/kg, p.o. was not ulcerogenic in rats.
5. These data show that AA-2379 is more active than non-acidic antiinflammatory agents, such as tiaramide and aminopyrine.

     

Inhibitory effects of methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl-2H-pyrazolo[3,4-d]pyrimidine-2-carboxylate (AA-2379) on lysozomal enzyme and arachidonic acid release from rat polymorphonuclear leukocytes and its mode of action

AA-2379 (methyl 7-butyl-4,5,6,7-tetrahydro-3-methylamino-4,6-dioxo-5-propyl-2H-pyrazolo[3,4-d]pyrimidine-2-carboxylate) has antiinflammatory, analgesic, and antipyretic activities, and inhibits the type III allergic (Arthus) reaction. In the studies reported here, we investigated the effect of AA-2379 on rat polymorphonuclear leukocyte (PMN) functions to clarify the mechanism of the antiinflammatory and antiallergic actions of AA-2379. AA-2379 at 10^?4 M inhibited lysozomal enzyme release. AA-2379 inhibits formyl methionyl-leucyl-phenylalanine (fMLP)- and C5a-induced arachidonic acid release; their 50% inhibitory concentrations were 2.8×10^?5 and 3.8×10^?5 M, respectively. Because dibutyryl cAMP, a cAMP analogue, and 3-isobutyl-1-methylxanthine, a cAMP phosphodiesterase inhibitor, inhibited fMLP-induced arachidonic acid release, and AA-2379 inhibited cAMP phosphodiesterase and increased cAMP content in PMNs, it is likely that AA-2379 inhibited arachidonic acid release by increasing cAMP content in rat PMNs. Furthermore, from the studies of fMLP-induced arachidonic acid release in Ca free medium it is suggested that AA-2379 inhibits the process which depends on Ca concentration in the medium. These results suggest that the inhibitory effect of AA-2379 on inflammation and allergic reactions such as the Arthus reaction is partly exerted by inhibiting PMN functions such as arachidonic acid and lysozomal enzyme release.     

Role of leukotrienes in rat reversed passive Arthus pleurisy and the effect of AA-861, a 5-lipoxygenase inhibitor

In studies of the role of leukotrienes in inflammatory reactions, the induction of rat reversed passive Arthus pleurisy (a type III allergic reaction) was employed. Increases of exudate volume, vascular permeability, and migration of inflammatory cells in the pleural cavity were observed. The vascular permeability was enhanced biphasically during 0-30 min (early response) and during 3-6 h (late response) after induction of the pleurisy. The infiltration of inflammatory cells, mainly polymorphonuclear leukocytes, into the cavity increased and reached a maximum 6 h after the pleurisy was induced. Leukotriene B4 (LTB4), 5-monohydroxyeicosatetraenoic acid (5-HETE), and slow-reacting substance of anaphylaxis (SRS-A), consisting of LTC4, LTD4 and LTE4, were detected in the exudate by reversed-phase high-performance liquid chromatography during the early response. The contents of LTC4 reached a maximum 10 min after the challenge, followed by a rapid decrease within 1 h. The rise and decay of LTC4 correlated with the increase in vascular permeability during the early phase. AA-861, a 5-lipoxygenase inhibitor, given intrapleurally inhibited the increase in vascular permeability, cell migration, and generation of leukotrienes during the early phase of the pleurisy. These results indicate that products of the 5-lipoxygenase pathway, such as LTC4 and LTB4, may play an important role as chemical mediators in the inflammatory reaction.     

Suppression of the Arthus reaction by Y-24180, a potent and specific antagonist of platelet-activating factor

A novel and potent antagonist of platelet-activating factor (PAF), Y-24180 (4-(2-chlorophenyl)-2-[2-(4-isobubylphenyl)ethyl]-6,9-dimethyl-6H-thieno[3,2-f][1,2,4]triazolo[4,3-a][1,4] diazepine) was investigated for the effects on the skin reactions induced by chemical mediators and the Arthus reactions. In the rat dorsal skin, Y-24180 (0.1–10 mg/kg, p.o.) inhibited increase in vascular permeability by the intradermal PAF injection in a dose dependent manner and the inhibitory activity was 60 times more potent than that of WEB 2086. While even at doses as large as 10 mg/kg, p.o., it had no effect on vascular permeability in the rat skin induced by histamine, serotonin, bradykinin and leukotriene D₄. On a reversed passive Arthus reaction in rat dorsal skin, Y-24180 (0.1–1 mg/kg, p.o.) markedly inhibited vascular permeability in a dose dependent manner and the inhibitory activity was 15 times more potent than that of WEB 2086. Y-24180 also inhibited the Arthus dermal reaction in rabbits (0.03–0.3 mg/kg, p.o.) and guinea pigs (0.1–1mg/kg, p.o.). In addition Y-24180 (0.1–10 mg/kg, p.o.) significantly reduced the exudate volume and the number of infiltrated inflammatory cells in the reversed passive Arthus pleural reaction in rats. Furthermore, in rat passive Arthus pancreatitis, Y-24180 (0.3–10 mg/kg, p.o.) significantly inhibited the dye extravasation from the pancreas. These results provide strong evidence that endogenous PAF plays an important role as a mediator in the type III allergic inflammation.     

The effects of (R)-N-(1-methyl-2-phenylethyl) adenosine (L-PIA), a standard A1-selective adenosine agonist on rat acute models of inflammation and neutrophil function

L-PIA, a standard A₁-selective adenosine agonist, was evaluated orally in carrageenan (CRG)- and reverse passive arthus-pleurisy. White blood cell (WBC) and exudate accumulation were assessed four hours after induction of the inflammatory response. L-PIA inhibited WBC accumulation in both models with ID₅₀'s of 4.37 and 4.42 mg/kg, respectively. In contrast, exudate was inhibited by L-PIA only in the CRG pleurisy model (ID₅₀=1.01 mg/kg). In mechanistic studies, L-PIA reversed the drop in circulating neutrophil count which occurred within 15 minutes after CRG injection, suggesting that L-PIA may inhibit adhesion of the cells to the endothelium. The effects of L-PIA on several parameters of rat neutrophil function were determined. Enzyme release, O ₂ ^– , TXB₂, and LTB₄ production were monitored in response to FMLP and opsonized zymosan (SOZ) stimulation. At high concentrations L-PIA had a mild inhibitory effect on O ₂ ^– release in response to FMLP and had a moderate effect on arachidonic acid metabolite production, in response to both stimuli. The other response were unaffected. These results suggest that L-PIA may prevent diapedisis or neutrophil adhesion to the endothelium, but has a minimal effect on enzyme release O ₂ ^– , LTB₄ and TXB₂ production.     

A model of Arthus pleurisy: modulation by various pharmacologic and therapeutic agents

A reversed passive Arthus reaction was elicited in the rat pleural cavity. The kinetics of this inflammatory response indicate that exudate volume (cells and fluid) reaches a maximum level approximately 2 to 4 hr postantibody challenge. The neutrophil is the major cellular constituent of the pleural exudate during the first 12 hr of this reaction, reaching peak values at 4 hr; whereas, the monocyte predominates between 15 and 24 hr. Lymphocytes, eosinophils, and mast cells were also identified in the pleural exudates. The serotonin antagonists, cyproheptadine and methylsergide, and the antihistamine, chlorpheniramine, demonstrated marginal activity in the Arthus pleurisy model. The histamine antagonist, metiamide, was inactive. The nonsteroidal anti-inflammatory agents, flurbiprofen, ibuprofen, indomethacin, and benoxaprofen caused a modest suppression of exudate volume (18-32%) and cell accumulation (28-34%). The fluid and cellular components of the Arthus reaction were significantly inhibited by dexamethasone, triamcinolone, paramethasone, and prednisolone. The oral gold preparation, auranofin, had a pronounced effect on exudate volume; whereas, other antirheumatic agents such as D-penicillamine, azathioprine, and chloroquine had no effect on the Arthus pleurisy reaction. The immunomodulator, levamisole, suppressed exudate volume, but had no effect on cell accumulation in the pleural cavity.     

Phospholipase A2-induced pleural inflammation in rats

Injection of Naja mocambique mocambique phospholipase A2 [PLA2] into the rat pleural cavity induced dose- and time-dependent fluid accumulation and cellular infiltration. The time course of the cell influx was initially neutrophilic [2-6 h] and later mononuclear [6-24 h]. During reverse passive Arthus reaction [RPAR] induced pleurisy, endogenously produced PLA2 activity, quantitated by the hydrolysis of [3H]-arachidonic acid E. coli substrate, was detected in the pleural exudate. However, the biosynthesis of eicosanoids and plasma extravasation in the pleural cavity preceded the 9-fold elevation in PLA2 activity which was obtained at 4 h. Whereas the exact role of PLA2 in the inflammatory response remains to be determined, these results demonstrate that exogenous PLA2 can induce pleural inflammation in the rat, and that this enzyme is released endogenously during experimental pleurisy.     

Anti-inflammatory effect of LA 2851 and reference drugs on some models of inflammation. Investigation of the mechanism of action

LA 2851 (2-4-diamino-7-methyl-pyrazolo (1,5-a), 1,3,5-triazine), a bronchodilator and antiallergic compound, in type I hypersensitivity, has been tested orally for activity against carrageenan oedema and complement dependent, reverse passive Arthus (RPA) and zymosan oedema in rats. Pharmacokinetic determinations were also realized in order to correlate plasma blood levels and pharmacological activity.LA 2851 was found active in the first test but showed a more marked effect in the immunologically mediated RPA reaction and zymosan oedema. Among reference drugs tested, theophylline showed the same pattern in contrast with non-steroidal anti-inflammatory agents. LA 2851 and theophylline, using a superfused lung preparation, were found ineffective on the synthesis of cyclooxygenase products from arachidonic acid.LA 2851 as theophylline inhibited cAMP phosphodiesterase (PDE) but this inhibition does not seem to be involved in their anti-inflammatory activity since papaverine, a potent inhibitor of PDE, was totally inactive. The activity on RPA and zymosan inflammation was achieved at the drug plasma level in the range of those required to relax the trachea. The same antagonism was obtained with the 2 drugs at a lower plasma level with LA 2851 than with theophylline for the same dose administered (25 mg/kg). LA 2851 and theophylline did not inhibit all the components of the inflammatory process since maximum inhibition did not exceed 60% up to 200 mg/kg and 100 mg/kg respectively.     

Ro 21-7634, a new antiallergic agent with potent oral activity

Ro 21-7634 was examined for oral antiallergic activity in two in vivo models commonly used to evaluate anti-allergics. In the rat PCA test, this drug had an oral ID₅₀ of 1.14 mg/kg and was found to be more potent than several other antiallergics including Disodium Cromoglycate (cromoglycate), Oxatomide, Doxanthrazole, Xanoxate, 2,6-bis (ethoxyoxalylamino) pyridine, PRD-92-EA and M+B 22,948. In contrast to cromoglycate, Ro 21-7634 was found to be an orally active inhibitor of antigen-induced bronchoconstriction in passively sensitized rats (ID₅₀=0.2 mg/kg). In addition, Ro 21-7634 inhibited antigen-induced histamine release in an in vivo passive peritoneal anaphylaxis test system, following intraperitoneal administration. Ro 21-7634 demonstrated no end organ antagonism toward histamine, methacholine or serotonin in the guinea pig.     

2,6-Di-tert-butyl-4-(2′-thenoyl)phenol(R-830): A novel nonsteroidal anti-inflammatory agent with antioxidant properties

R-830, a di-tert-butylphenol, has been shown to be anti-inflammatory in a number of animal models. These include conventional systems such as carrageenan-induced edema and adjuvant arthritis of the rat and ultraviolet-induced erythema in the guinea pig in which the acidic nonsteroidal anti-inflammatory drugs (e.g., indomethacin) are effective. The anti-inflammatory activity of R-830 has also been demonstrated in other models (e.g., graft vs. host reaction and reversed passive cutaneous Arthus reaction in the rat, contact sensitivity in the mouse) in which the acidic nonsteroidal drugs are not effective.In vitro, R-830 inhibits guinea pig lung lipoxygenase and bovine seminal vesicle cyclo-oxygenase. The antioxidant properties of R-830 were demonstrated in twoin vitro systems. We speculate that the antioxidant activity of this molecule might be related to its unusual profile of pharmacological activity.     

Pharmacological properties of N-methoxy-3-(3,5-ditert-butyl-4-hydroxybenzylidene)-2-pyrrolidone (E-5110), a novel nonsteroidal antiinflammatory agent

The antiinflammatory activity of a novel pyrrolidone derivative E-5110 was investigated using anti-inflammatory, analgesic and antipyretic animal models in comparison to indomethacin (IND) and piroxicam (PIR). The acute antiinflammatory activity of E-5110 on carrageenin paw edema was similar to IND, and half of PIR. E-5110 inhibited the pleural exudate volume and leucocyte infiltration in a reversed passive Arthus reaction more potent than IND. The chronic inflammatory responses in the established adjuvant- and type II collagen-induced arthritis were suppressed by E-5110 similar to IND and PIR. The analgesic potency of E-5110 was similar to IND and PIR, but the antipyretic activity of E-5110 was more potent than that of IND, and slightly more potent than that of PIR. The ulcerogenic effect of E-5110 on rat gastric mucosa was less than that of the reference drugs.     

Complement and polymorphonuclear leukocytes do not determine the vascular permeability induced by intraocular LPS.

The intravitreous injection of an endotoxin of Escherichia coli 055:B5 (LPS; 0.1-0.5 microgram/50 microliters of saline) induces ocular inflammation in rabbits that is maximal 20-24 hours later and disappears by 4 days. The inflammation is characterized by an alteration in ocular vascular permeability (OVP) measured by the ocular extravasation of 125I-albumin and an outpouring of leukocytes, most of which are polymorphonuclear leukocytes (PMNs), as determined by histopathologic study. Nitrogen mustard (mechlorethamine, 1.75 mg/kg) administered 3 days prior to LPS virtually eliminates PMNs in the circulation and those infiltrating ocular tissues 20 hours after intravitreous LPS, and yet the average increase in vascular permeability is not different from that of controls. Cobra venom factor (CVF; 300-400 units) 7 hours before intravitreous LPS produces a greater than 90% decrease in both hemolytic complement activity and zymosan-inducible serum chemotactic activity; yet 20 hours after LPS, the OVP is the same in CVF-treated rabbits and controls. For comparison, an ocular passive Arthus reaction (ovalbumin-anti-ovalbumin) was significantly affected by CVF pretreatment. Chemotactic activity in the aqueous humor is found in both CVF-treated and control rabbits 20 hours after intravitreous LPS. This activity attracts rabbit, but not human, PMNs, is partially heat-sensitive, and is not inhibited when PMNs are preincubated with C5a. These results indicate that neither PMNs nor circulating complement determine the OVP following intravitreous LPS, and that the chemotactic activity present in aqueous humor at the height of the inflammatory response is not primarily C5a.     

Evidence that platelet activating factor may mediate some acute inflammatory responses. Studies with the platelet-activating factor antagonist, CV3988

Platelet activating factor (PAF) has many proinflammatory properties. It is a polymorphonuclear leukocyte chemotactic factor, it aggregates platelets, increases vascular permeability, and is generated by inflammatory cells. To determine the possible in vivo role of PAF in inflammation, we examined the effects of the PAF antagonist and structural analogue, CV3988 on acute inflammatory responses in the skin of rabbits. Initial experiments indicated that CV3988 (10 mg/kg) was a specific inhibitor of PAF responses in vivo since it abolished neutropenia and thrombocytopenia induced by intravenous (iv) PAF infusion without effecting the response to f-met-leu-phe. In dermal inflammation, 125I-albumin, 111In-labeled platelets, 51Cr-labeled leukocytes, and 86RbCl were used to simultaneously quantitate protein exudation, platelet deposition, leukocyte accumulation, and blood flow in the lesions. CV3988 inhibited inflammatory responses to intradermal injection of PAF by 65 to 85% but it did not inhibit thrombin-induced platelet deposition or bradykinin and histamine-induced protein exudation. CV3988 treatment inhibited by 60 to 80% (p less than 0.01) the platelet deposition occurring at the peak of the reaction (1 1/2 hours) induced by the intradermal injection of zymosan, zymosan activated plasma, endotoxin, and the reversed passive Arthus reaction. Protein exudation was inhibited by 67 to 85% (p less than 0.1) and leukocyte accumulation was inhibited by 24 to 35% (p less than 0.05), but only in the zymosan and reversed passive Arthus reactions, respectively. Inflammatory hyperemia (increases blood flow) was not affected by CV3988 treatment. We conclude that in certain inflammatory reactions, PAF may mediate platelet deposition and protein exudation. The marginal effect of CV3988 on leukocyte accumulation suggests that the leukotactic activity of PAF is relatively less important in vivo.     

Comparison of the effect of various antisera and cobra venom factor on inflammatory reactions in guinea-pig skin. II. The Arthus reaction and the local Shwartzman reaction.

The ability of antisera to guinea-pig C3 to inhibit the Arthus and local Shwartzman reactions was studied. They were found to reduce the non-haemorrhagic component of the active and reversed passive Arthus reactions and to delay the appearance of the haemorrhage in the active Arthus reaction. Cobra venom factor, however, had no effect on the non-haemorrhagic components of these reactions and only delayed the appearance of the haemorrhage of the active Arthus reaction. There appeared to be a correlation between the serum complement level and the time taken for the haemorrhage to appear, and between the circulating platelet count and the extent of the non-haemorrhagic, oedematous component of the reaction. The haemorrhagic component of the local Shwartzman reaction was not affected by decomplementation with cobra venom factor. The ability of the antisera to inhibit the haemorrhage of the Shwartzman reaction was not dependent on lowering the serum complement titre. However, the haemorrhage was inhibited if the circulating platelet count was also reduced to very low numbers. Antiserum to zymosan alone had the same effect as anti-beta1C/beta1A globulin (zymosan) in blocking the reaction, although it did not alter the complement levels or the platelet counts. The possibility of an immunological cross-reactivity between zymosan and endotoxin in this action is discussed.     

Leukotriene B4 production and pharmacologic regulation of reverse passive Arthus pleurisy: Importance of antigen dose

Immunoreactive leukotriene B₄ (iLTB₄), detected in the pleural cavity following induction of a reverse passive Arthus reaction (RPAR), was inhibited by the mixed lipoxygenase-cyclooxygenase inhibitors, phenidone and BW 755C, but not by cyclooxygenase inhibitors or by chlorpheniramine or methysergide. Both iLTB₄ production and the subsequent pleural inflammation were dependent upon the dose of BSA antigen employed to elicit the RPAR pleurisy. However, inasmuch as BW 755C and phenidone were not distinguished from the cyclooxygenase inhibitors in their effects on fluid accumulation and cellular infiltration in RPAR pleurisy, it is doubtful that LTB₄ plays a functional role in this inflammation model.     

The effect of anti-inflammatory compounds on the biochemical changes in the Arthus reaction.

The effect of anti-inflammatory drugs on the biochemical changes in the Arthus reaction have been studied and correlated to changes in the pathology of the reaction. In the Arthus reaction all the non-steroidal anti-inflammatory drugs inhibited the migration of cells into the lesion and reduced the lysosomal enzyme concentration at the Arthus site. The steroids did not inhibit the cellular inflitration or the total lysosomal enzyme concentration in the skin but did reduce the concentration of cathepsin D in the oedema fluid. In addition, prednisolone and, to a lesser extent, hydrocortisone reduced the degree of oedema formation. The results suggest that non-steroidal anti-inflammatory drugs inhibit the Arthus reaction by reducing the cellular infiltration whereas anti-inflammatory steroids act by preventing these cells secreting their lysosomal enzymes and thus causing tissue damage.     

The activity of an anti-allergic compound,proxicromil, on models of immunity and inflammation

A tricyclic chromone, proxicromil (sodium 6,7,8,9-tetrahydro-5-hydroxy-4-oxo-10-propyl-naphtho (2,3-b) pyran-2-carboxylate), has been tested for activity against certain immunological and inflammatory reactions.When given parenterally it suppressed the development of delayed hypersensitivity reactions in sensitized mice and guinea-pigs but did not affect the rejection of skin allografts in mice. The compound had no activity against certain in vitro correlates of delayed hypersensitivity reactions (lymphocyte transformation and lymphokine activity), but did have an inhibitory effect on lymphokine (MIF) production at 10^–4 M but not at 10^–5 M.Proxicromil was also found to be active in non-immunologically mediated models of inflammation and in models having an immunological component which are known to be sensitive to non-steroidal anti-inflammatory drugs (adjuvant arthritis, reversed passive Arthus reaction).The activity of this compound was enhanced when administered in arachis oil when compared to its activity in saline.Proxicromil has no direct activity on the development of immune responsiveness but appears to suppress the expression of delayed hypersensitivity and immune complex mediated hypersensitivity reactions by virtue of its anti-inflammatory properties. This activity is not associated with inhibition of cyclo-oxygenase.     

Differential effects of pharmacologic agents on the reverse passive Arthus reaction in guinea pigs

Five different pharmacologic agents were examined for their effects upon edema, hemorrhage, and vascular infiltration by neutrophils in the reverse passive Arthus reaction (RPAR) in guinea pigs.Two agents, colchicine (3.0 mg/kg p.o.) and ibuprofen (100 mg/kg p.o.) significantly inhibited all three parameters of RPAR. Cobra venom factor (100 units/kg i.p.) inhibited edema and hemorrhage but it did not inhibit neutrophil infiltration. Aminophylline and sulfinpyrazone (100 mg/kg p.o.) inhibited only hemorrhage; they did not inhibit edema or neutrophil infiltration.The results from these studies with five chemically or biologically unrelated pharmacologic agents suggest that the RPAR in guinea pigs can be separated into its basic components (edema, hemorrhage, and neutrophilic infiltration) by selective inhibitors. inhibition of edema and hemorrhage, or hemorrhage alone of the two-hour RPAR in guinea pigs is not dependent upon inhibition of neutrophilic infiltration.     

The arthus reaction in rats,a possible test for anti-inflammatory and antirheumatic drugs

The Arthus reaction is an immunologically induced inflammatory response characterized by immune complex deposition, complement fixation, polymorphonuclear leukocyte infiltration and tissue damage. Many of these same pathological tissue alterations are found in the lesions of rheumatoid arthritis (RA). The similarities between the reversed passive Arthus reaction (RPAR) and RA led us to investigate the usefulness of the RPAR in the search for new antirheumatic agents. The RPAR was elicited in the skin of rats using chicken ovalbumin and the IgG fraction of rabbit anti-ovalbumin. Paramethasone, hydrocortisone, indomethacin, pirprofen, sulfinpyrazone, thalidomide and theophylline all gave significant inhibition of the RPAR. Ibuprofen, naproxen, cyproheptadine and cromolyn sodium were inactive, while phenylbutazone and ASA exhibited a dose-dependent effect. The data show that the Arthus reaction, which is the result of the complex interaction of many factors, can be affected either generally or selectively at different time intervals by various therapeutic agents. The RPAR in rats may prove useful in detecting new therapeutic agents for the treatment of RA.     

Inhibition of hypersensitivity reactions by a new drug, N(3',4'-dimethoxycinnamoyl) anthranilic acid (N-5').

N (3', 4'-dimethoxycinnamoyl) anthranilic acid (N-5'), a new antiallergic drug, can be taken orally, has low toxicity, and is a potent inhibitor of homologous passive cutaneous anaphylaxis (PCA) both in rats and in guinea pigs. Anaphylactic mediator release from guinea pig lung was decreased by the drug in vitro. Although reversed cutaneous anaphylaxis and Arthus type reactivity were moderately inhibited with N-5', this agent did not inhibit the Forssman systemic reaction or contact dermatitis. N-5' is considered to be clinically applicable to certain allergic-related diseases, in particular asthma caused by reaginic antibody.