Compounds of a formula (I)[wherein, A represents formula (III-1)R3 is a hydrogen, lower alkyl et al； m is 0 or 1； R1 is a hydrogen atom, halogen atom et al, R2 is a hydrogen et al； p is 0 to 4； X is a carbon atom or nitrogen atom； and X1 to X4 is a lower alkyl et al], or pharmaceutical acceptable salts thereof. These have a potency antagonistic to binding to histamine H3 receptor, or have a potency inhibiting the constant activity of histamine H3 receptor, and are useful in the therapy of obesity, diabetes et al.
