1. The use of a compound with antagonistic activity against the EP4 receptor, or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of IL-23-mediated diseases in an animal subject, including a mammalian subject； 2. The use of a compound of formula (I), (II), (III), (IV), (Va) or (Vb), or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for the treatment of IL-23-mediated diseases in an animal subject, including a mammalian subject: [Chemical structure 21] where Y, Y, Y, and Y are independently selected from N, CH and C (L)； R is H, C1-6alkyl, Salkenyl, Salkynyl, Cycloalkyl, Salkoxy, halogen-substituted Salkoxy , C1-6alkyl-S (O) m-group, Q-group, pyrrolidinyl, piperidyl, oxopyrrolidinyl, oxopiperidyl, amino, mono- or di- (C1-6alkyl) amino a group, C1-6alkyl-C (= O) -N (R) -group, or C1-6alkyl-S (O) mN (R) -group, wherein said C1-6alkyl, C1-6alkenyl and C1-6alkyl is optionally substituted with halogen, C1-6alkyl, hydroxy, oxo, C1-4 alkoxy, C1-6alkyl -S (O) m-group, Cycloalkyl, cyano, indanyl, 1,2,3,4-tetrahydronaphthyl, 1,2-dihydronaphthyl, pyrrolidinyl, piperidyl, oxopyrrolidinyl, oxopiperidyl, Q-group, Q-C (= O) -group, Q-O-group, QS (O) m-group, Q-Ci-alkyl-O-group, Q-Ci-alkyl-S (O) m-group, Q-Ci-alkyl-C (O) -N (R) -group, Q-C1-6 alkyl-N (R) -group, or C1-6-alkyl (C) -N (R) -group； Q is a 5-12 membered m notsiklicheskoe or bicyclic aromatic ring optionally containing up to 4 heteroatoms selected from O, N and S, and optionally substituted by halogen, alkylene, halo-substituted alkylene, hydroxy group, alkoxy group, halogen-substituted alkoxy-group1. Применение соединения с антагонистической активностью в отношении рецептора ЕР4, или его фармацевтически приемлемой соли в изготовлении лекарственного препарата для лечения IL-23-опосредованных заболеваний у субъекта-животного, в том числе у субъекта-млекопитающего；2. Применение соединения формулы (I), (II), (III), (IV), (Va) или (Vb), или его фа
