A heterocyclic-substituted oxoalkanoic acid derivative having immunomodulatory activities of the formula: ##STR1## wherein R.sup.1 is hydrogen, lower alkyl, phenyl which may be substituted by at least one substituent selected from halogen, lower alkyl, lower alkoxy, mono- or di-lower alkyl amino-substituted lower alkoxy, lower alkylthio, lower alkylsulfinyl, amino, nitro and cyano at any position(s) on the nucleus, thienyl or furyl, each of R.sup.2 and R.sup.3 is hydrogen or lower alkyl, A is lower alkylene, X is sulfur or vinylene, Y is nitrogen or methine which may be substituted by lower alkyl, Z is carbonyl or direct bond.