Combination of iap inhibitor and immune checkpoint inhibitor

A combination, comprising a compound represented by formula (I), an isomer thereof or a pharmaceutically acceptable salt thereof, and an immune checkpoint inhibitor,

• wherein,
• X1 is selected from C(R5) and N;
• X2 is selected from C(R6), N, O, and S;
• is selected from a single bond and a double bond;
• L is selected from a single bond and —O—;
• R1 is selected from —C(═O)NH2, CN, C1-5 alkyl, C1-5 heteroalkyl, phenyl, 5- to 6-membered heteroaryl, and 5- to 6-membered heterocycloalkyl;
• the C1-5 alkyl, C1-5 heteroalkyl, phenyl, 5- to 6-membered heteroaryl and 5- to 6-membered heterocycloalkyl are optionally substituted with 1, 2 or 3 R;
• R2 is selected from H, halogen, CN, COOH, —C(═O)NH2, C1-4 alkyl, and C1-4 heteroalkyl;
• the C1-4 alkyl and C1-4 heteroalkyl are optionally substituted with 1, 2 or 3 R;
• R3 and R7 are each independently selected from H, halogen and C1-4 alkyl;
• the C1-4 alkyl is optionally substituted with 1, 2 or 3 R;
• R4 is selected from H, phenyl, and 5- to 6-membered heteroaryl;
• R5 is selected from H and halogen;
• R6 is selected from H, halogen, C1-4 alkyl, C1-4 heteroalkyl, CN, and COOH;
• the C1-4 alkyl and C1-4 heteroalkyl are optionally substituted with 1, 2 or 3 R;
• R is selected from halogen, OH, CN, CH3, CH3CH2, CH3CH2CH2, CH(CH3)2, OCH3, OCF3, CHF2, CH2F, and NH2;
• and
• the C1-4 heteroalkyl, C1-5 heteroalkyl, 5- to 6-membered heterocycloalkyl and 5- to 6-membered heteroaryl each contain 1, 2 or 3 heteroatoms or heteroatom radicals independently selected from —NH—, —O—, —S—, N, —C(═O)O—, —C(═O)—, —C(═O)NH—, —C(═S)—, —S(═O)—, —S(═O)2—, —C(═NH)—, —S(═O)2NH—, —S(═O)NH—, and —NHC(═O)NH—.