Ro 21-7634, a new antiallergic agent with potent oral activity.

Ro 21-7634 was examined for oral antiallergic activity in two in vivo models commonly used to evaluate anti-allergics. In the rat PCA test, this drug had an oral ID50 of 1.14 mg/kg and was found to be more potent than several other antiallergics including Disodium Cromoglycate (cromoglycate), Oxatomide, Doxanthrazole, Xanoxate, 2,6-bis (ethoxyoxalylamino) pyridine, PRD-92-EA and M+B 22,948. In contrast to cromoglycate, Ro 21-7634 was found to be an orally active inhibitor of antigen-induced bronchoconstriction in passively sensitized rats (ID50=0.2 mg/kg). In addition, Ro 21-7634 inhibited antigen-induced histamine release in an in vivo passive peritoneal anaphylaxis test system, following intraperitoneal administration. Ro 21-7634 demonstrated no end organ antagonism toward histamine, methacholine or serotonin in the guinea pig.