NEW MATERIAL: A compd. represented by formula I [wherein Ra is H, halogen, hydroxy, CN or 1-6C alkyl; Rb is H or 1-6C alkyl; Rc is H, 1-8C alkyl or 3-8C alkenyl; and Y is 1-8C alkyl or 3-8C alkenyl), its salt and its 1-4C alkoxycarbonyl deriv.

EXAMPLE: 1,2-Dihydro-2-methyl-4-(N-methylcarbamoyl)-3H-indazol-3-one.

USE: A riboxygenase inhibitor. Useful as a remedy of leucotriene mediated allergy symptoms, asthma, cardiovascular disorder and cerebrovascular disorder.

PROCESS: A compd. represented by formula II (Rd is a protective group) is treated to remove a protective group and, when a salt is required, the obtained compd. is reacted with a proper acid or base by a usual method to obtain the compd. represented by formula I.