Mechanisms of non-drowsiness after oral administration of TMK688, a novel antiallergic drug.

The mechanisms of non-drowsiness after oral administration of TMK688 (1- [[5'-(3"-methoxy-4"-ethoxycarbonyloxyphenyl)-2',4'-pentadienoyl ] aminoethyl]-4-diphenylmethoxypiperidine, CAS 110501-66-1) were investigated using mice. TMK688 inhibited the histamine-induced vascular permeability at oral doses of 3.2-10 mg/kg with an ID50 value of 5.4 mg/kg. More than 100 times higher doses were needed to prolong the hexobarbital-induced sleeping. Pyrilamine, a typical antihistamine agent, showed little difference among these doses and antiallergic drugs having antihistamine activity, i.e., terfenadine, azelastine and ketotifen, had effects between TMK688 and pyrilamine. The inhibitory activity of orally administered TMK688 against ex vivo [3H]-pyrilamine binding to mouse cerebral histamine receptors appeared at the same doses as its potentiating activity against hexobarbital-induced sleeping. When given orally, TMK688 was hydrolyzed to TMK777 (CAS 101619-11-8), then conjugated with glucuronic acid to TMK777-glucuronide. No TMK688 was detected in the blood. The main metabolite TMK777-glucuronide could hardly penetrate the blood-brain barrier because of its polarity. Although the plasma concentrations of TMK777 were far lower than those of TMK777-glucuronide, TMK777 was penetrable into the brain and the cerebral concentrations of TMK777 increased in parallel with the plasma concentrations of the drug. Since intracerebroventricularly-injected TMK777 prolonged the sleeping time, and since the threshold concentration of TMK777 in the cerebral cortex to potentiate the hexobarbital-induced sleeping was consistent despite different administration routes, the drowsiness elicited by markedly high doses of TMK688 is though to be caused by intracerebral TMK777. In other words, TMK688 does not seem to cause drowsiness at effective doses because of the poor prenetrability of its main metabolites into the brain.

The inhibitory effect of TMK688, a novel anti-allergic drug having both 5-lipoxygenase inhibitory activity and anti-histamine activity, against bronchoconstriction, leukotriene production and inflammatory cell infiltration in sensitized guinea pigs.

BACKGROUND: TMK688 is being developed as an anti-allergic drug having both 5-lipoxygenase inhibitory activity and anti-histamine activity. METHOD: We compared the inhibition of the late asthmatic responses by TMK688 with that by other anti-allergic agents in actively sensitized guinea pigs, and examined the relationship between 5-lipoxygenase inhibition and the late asthmatic responses. RESULTS: At 1-3.2 mg/kg, TMK688 inhibited the increases in respiratory resistance, leukotriene (LT) B4 and C4 production in the lungs and eosinophil infiltration into the alveoli during the late asthmatic response, whereas the effects tended to lessen at the dose of 10 mg/kg. These effects are thought to be caused by the 5-lipoxygenase inhibitory activity of TMK688 because Azelastine, an anti-allergic drug having potent antihistamine activity, exhibited no effect. ONO-1078, a peptide LT antagonist, inhibited the late-phase bronchoconstriction at a dose of 100 mg/kg p.o., but not the increase in the infiltration of inflammatory cells into the alveoli, suggesting that the late-phase bronchoconstriction is induced, in part, by peptide LTs, i.e. LT C4, D4 and E4 and that the inflammatory cell infiltration may be caused by LTB4. TMK688 inhibited the immediate bronchoconstriction dose-dependently, and the effect was significant at a dose of 10 mg/kg orally. Since Azelastine, Ketotifen and Oxatomide suppressed the bronchoconstriction at far lower doses than did TMK688, the inhibitory effect was mainly caused by its antihistamine activity. CONCLUSIONS: TMK688 appears to be a novel anti-allergic drug having inhibitory effects on both the bronchoconstriction and the infiltration of inflammatory cells during late asthmatic responses.

Effects of TMK688, a novel anti-allergic drug, on allergic nasal obstruction and exudative responses in sensitized guinea pigs.

TMK688 (1-[[5'-(3"-methoxy-4"-ethoxycarbonyloxyphenyl)-2',4'-pentadien oyl] aminoethyl]-4-diphenylmethoxypiperidine) is being developed as an orally effective antiallergic drug having both 5-lipoxygenase inhibitory activity and anti-histamine activity (Shizawa et al. 1996; Tohda et al. 1997). The efficacy of TMK688 against allergic rhinitis was examined in passively sensitized guinea pigs. TMK688 inhibited the increase in intranasal resistance following antigen challenge at doses of 1 and 3.2 mg/kg p.o. The allergic nasal obstruction was also suppressed by 10 mg/kg i.v. of FPL-55712, a peptide leukotriene receptor antagonist, but not by 3.2 mg/kg i.v. pyrilamine, a histamine H1 receptor antagonist, or by 10 mg/kg p.o. of ketotifen, an anti-allergic drug having anti-histamine activity, suggesting that the nasal obstruction was caused by leukotrienes. Following antigen challenge, the intranasal release of leukotrienes B4 and C4, and histamine increased in passively sensitized guinea pigs. TMK688 tended to suppress the increase in immunoreactive leukotrienes B4 and C4 in the nasal lavage fluid at a dose of 1 mg/kg p.o., and significantly inhibited the increase at 3.2 mg/kg. The brilliant blue dye leakage following antigen challenge from the blood stream into the nasal cavities was significantly inhibited by not only TMK688 and FPL-55712 but also pyrilamine, suggesting that the allergic dye leakage was caused cooperatively by leukotrienes and histamine. However, ketotifen showed no significant suppression of the dye leakage even at 10 mg/kg p.o., although this drug inhibited the histamine-induced dye leakage at far lower doses (0.1 mg/kg p.o. or higher) in unsensitized guinea pigs. Therefore, histamine is not necessarily the major mediator of allergic dye leakage in our experiment. These findings demonstrate that TMK688 may be superior to antihistamines as a therapeutic agent for allergic rhinitis.

5-Lipoxygenase inhibitory and antihistamine activities of linetastine.

The ability of linetastine (TMK688, 1-[¿5'-(3"-methoxy-4"-ethoxycarbonyloxyphenyl)-2',4'-pentadieno yl¿ aminoethyl]-4-diphenylmethoxypiperidine, CAS 110501-66-1) to inhibit leukotriene production and to antagonize the effect of histamine was examined in comparison with the ability of azelastine, an antiallergic drug having an antihistamine activity. Linetastine and its active metabolite TMK777 (1-[¿5'-(3"-methoxy-4"-hydroxyphenyl)-2',4'-pentadienoyl¿ aminoethyl]-4-diphenylmethoxypiperidine, CAS 101619-11-8) inhibited the release of leukotrienes B4 and C4 from calcium ionophore-stimulated human leukocytes. The respective IC50 values of leukotriene B4 were 1.2 x 10(-7) mol/l and 8.6 x 10(-8) mol/l, and those of leukotriene C4 were 1.5 x 10(-7) mol/l and 7.1 x 10(-8) mol/l. Azelastine also inhibited the release of leukotriene B4 and C4, but its IC50 values were higher than 1 x 10(-5) mol/l. Linetastine at 1-10 mg/kg p.o. inhibited the increase in leukotriene B4 and C4 production in the lungs during late asthmatic responses in actively sensitized guinea-pigs. The effect of 3.2 mg/kg lasted for more than 16 b. Since repeated oral administration of linetastine, 1 mg/kg once a day for 7 successive days, showed the same inhibitory effect on the increase in respiratory resistance and the leukotriene production as single oral administration, the effect of linetastine was neither tachyphylactic nor cumulative. Azelastine at 10 mg/kg had no effect on the leukotriene production. Linetastine TMK777 and azelastine dose-dependently inhibited the histamine-induced contraction of isolated guinea-pig trachea in a noncompetitive manner, the respective pD2 values were 7.28, 7.98 and 8.07. Linetastine inhibited histamine-induced bronchoconstriction dose-dependently at 1-10 mg/kg (p.o.) in guinea-pigs, and the effect lasted for more than 24 h. Repeated oral administration of linetastine, 0.32 to 3.2 mg/kg once a day for 7 successive days inhibited the histamine-induced bronchoconstriction, the same as single oral dosing. Azelastine at 0.32 mg/kg p.o. also showed antihistamine activity. In conclusion, linetastine inhibits both the production of leukotrienes and the effect of histamine at almost the same dose and the effects were long lasting.