Immunopharmacological actions of the new antiallergic drug 11-oxo-11H-pyrido[2,1-b]quinazoline-2-carboxylic acid. Effects on type I hypersensitivity reactions in human leukocytes and in human and monkey lungs.

The effects of 11-oxo-11H-pyrido[2,1-b]-quinazoline-2-carboxylic acid (Sm 857), a new antiallergic drug, on histamine release from human leukocytes and from human and monkey lungs were investigated. Sm 857 dose-dependently inhibited histamine release induced by mite antigen, anti-human IgE, calcium ionophore A23187 (A23187) and protein A from peripheral leukocytes of atopic patients, but had no effect on the levels of cyclic AMP and GMP in human leukocytes. In addition, antigen- or anti-human IgE-induced anaphylactic histamine release from human and monkey lung fragments passively sensitized with human reaginic serum sensitive to mite antigen as well as A23187-induced histamine release from non-sensitized monkey lung fragments, were inhibited dose-dependently by Sm 857. However, no inhibition of spontaneous histamine release from human leukocytes or monkey lung fragments by Sm 857 was observed.