Described is a pyridine derivative represented by the following formula (1): ##STR1## wherein R.sup.1 and R.sup.2 individually represent H, an alkyl group, a cycloalkyl group, a hydroxyalkyl group, an alkoxyalkyl group which may have a substituent, a carboxyalkyl group, an alkoxycarbonylalkyl group, an aralkyl group which may have a substituent, a phenacyl group or an acyl group, R.sup.3 represents an alkyl group, a phenyl group which may have a substituent, a heteroaryl group or a cyclic amino group, X represents O or combination of OH and H, or a salt thereof; and a medicament, such as cytokine production suppressant, comprising the derivative or salt thereof as an effective ingredient. The invention compound has potential, highly specific and highly safe immunoregulating capacity so that it can suppress the excessive production of a specific cytokine in various diseases related to the immune system.