Abstract: The present invention relates to a novel pyrido[4,3-d]pyrimidine derivative having the formula (I): ##STR1## wherein each of R.sub.1 and R.sub.2, which may be the same or different, is a lower alkyl group; R.sub.3 is hydrogen, halogen, hydroxy, amino, hydroxyamino, imino, hydrazino or a lower alkylamino group which may optionally have hydroxy, amino or a lower alkylamino group; and R.sub.4 is hydrogen, amino, --NH.sup..crclbar. or a lower alkyl group which may optionally have hydroxy, amino or a lower alkylamino group; and pharmaceutically acceptable salt thereof. These compounds are useful as anti-allergic agents, for example, for the treatment of bronchial asthma, urticaria, allergic rhinitis, allergic dermatoses or allergic conjunctivitis.

Abstract: The present invention relates to a novel pyrido[2,3-d]pyrimidine derivative having the formula (I): ##STR1## wherein each of R.sub.1 and R.sub.2, which may be the same or different, is a lower alkyl group; and each of R.sub.3 and R.sub.4, which may be the same or different, is hydrogen, halogen, hydroxy, nitro, amino, hydroxyamino, hydrazino, azido, a lower alkenylamino group or a lower alkylamino group which may optionally have hydroxy; and pharmaceutically acceptable salt thereof. These compounds are useful as anti-allergic agents, for example, for the treatment of bronchial asthma, urticaria, allergic rhinitis, allergic dermatoses or allergic conjunctivitis.