Since β-tryptase is considered a critical mediator of asthma, potent tryptase inhibitors may be useful as new agents for the treatment of asthma. We investigated 4-substituted benzylamine derivatives and obtained M58539 (15h) as a potent inhibitor of β-tryptase (IC50= 5.0 nM) with high selectivity against other serine proteases, low molecular weight, clogP value less than 5, lack of amidino and guanidino groups, and independence of ...