Bamirastine inhibits ligand binding to recombinant human histamine H1 receptor (rhH1R) with an IC50 of 17.3 nM and possesses an inhibitory effect on allergic skin inflammation.

H1 receptor (recombinant human):17.3 nM

In a concentration-dependent manner, Bamirastine (TAK-427) reduces the specific binding of [3H] pyrilamine to recombinant human H1 receptors (rhH1R) with an IC50 value of 17.3 nM. The calculated Ki value for this interaction is 7.35 nM. Notably, the affinity of Bamirastine is determined to be as high as that of azelastine, 2 times lower than that of Epinastine, 8 times lower than that of ketotifen, and 3 times higher than that of Terfenadine[1].

Bamirastine (TAK-427) exhibits inhibition of histamine-induced skin reactions in guinea pigs and mice, with ID50 values of 0.884 and 0.450 mg/kg, p.o., respectively. Notably, significant inhibition persists 24 hours after dosing in guinea pigs even at a dose of 10 mg/kg. However, even at a high dose of 300 mg/kg, Bamirastine does not affect pentobarbital-induced sleeping time in mice.
Furthermore, Bamirastine significantly inhibits passive cutaneous anaphylaxis (PCA) in both mice and guinea pigs. Additionally, it inhibits antigen-induced immediate skin reactions (ISRs) in guinea pigs[1].