Ring-modified proline short peptide compound and use thereof

A compound represented by formula (X) or a pharmaceutically acceptable salt thereof,

• wherein,
• G is selected from
• ring A is selected from C3-10 cycloalkyl, 3- to 10-membered heterocycloalkyl, C6-10 aryl and 5- to 10-membered heteroaryl;
• R1 is each independently selected from halogen, OR11, CN, CH3S(O)m—, —NH(R12), C1-3 alkyl and C1-3 haloalkyl;
• R11 is selected from H, C1-3 alkyl, C1-3 haloalkyl, CH3(OCH2CH2)p— and H(OCH2CH2)q—;
• R12 is selected from C1-3 alkyl, C1-3 haloalkyl, CH3CO— and CH3SO2—;
• m is selected from 0, 1 and 2;
• p and q are selected from 1, 2, 3, 4, 5 and 6;
• n is selected from 0, 1, 2, 3 and 4;
• X is selected from —CH(R3)—, —CH2CH2—, O, S, Se, SO2 and —N(R3)—, and the —CH2CH2— is optionally substituted by 1, 2, 3 or 4 R;
• R is each independently selected from halogen, OH, NH2, CN, C1-3 alkyl and C1-3 haloalkyl;
• R3 is each independently selected from H, C1-3 alkyl, C1-3 alkoxy, C1-3 haloalkyl, C1-3 haloalkoxy, C6-10 aryl and 5- to 10-membered heteroaryl, and the C6-10 aryl and 5- to 10-membered heteroaryl are optionally substituted by 1, 2 or 3 R31;
• R2 and R4 together with the atoms to which they are attached form C5-8 cycloalkyl, 5- to 6-membered heterocycloalkyl or 5- to 6-membered heterocycloalkenyl, and the C5-8 cycloalkyl, 5- to 6-membered heterocycloalkyl or 5- to 6-membered heterocycloalkenyl is optionally and independently substituted by 1 or 2 Ra;
• Ra is each independently selected from H, halogen, C1-3 alkyl, C1-3 alkoxy, C1-3 haloalkoxy, C3-6 cycloalkyl, C6-10 aryl and 5- to 10-membered heteroaryl, and the C3-6 cycloalkyl, C6-10 aryl and 5- to 10-membered heteroaryl are optionally substituted by 1, 2 or 3 R41;
• R21, R31 and R41 are each independently selected from halogen, OH, NH2, CN, C1-3 alkyl, C1-3 alkoxy, C1-3 haloalkyl and C1-3 haloalkoxy;
• R5 is selected from C1-3 alkyl, C1-3 haloalkyl, C1-3 alkoxy, C1-3 haloalkoxy, —CH2—R6 and —CH2—O—R6;
• R6 is selected from phenyl, and the phenyl is optionally substituted by 1, 2 or 3 R61;
• R61 is selected from halogen, C1-3 alkyl, C1-3 haloalkyl, C1-3 alkoxy and C1-3 haloalkoxy.