Compound used as RET kinase inhibitor and application thereof

A compound, or a pharmaceutically acceptable salt, stereoisomer, or solvate thereof has a structure represented by Formula 6′,

• wherein X2, X9, and X10 are each independently selected from N or CR5;
• X7 and X8 are each independently selected from N or C;
• and
• R5 is each independently selected from hydrogen, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C1-C6 alkoxy, C1-C6 alkylamino, halogen, C1-C6 heteroalkyl, cycloalkyl, nitro, cyano, or amino;
• wherein alkyl, alkenyl, alkynyl, alkoxy, alkylamino, heteroalkyl, and cycloalkyl are each independently substituted by 0-5 Ra;
• Ra is selected from C1-C6 alkyl, halogen, hydroxy, C1-C6 heteroalkyl, C1-C6 alkoxy, C1-C6 alkylamino, cycloalkyl, heterocycloalkyl, or cyano;
• ring Q2 is selected from five-membered, six-membered or seven-membered saturated ring, unsaturated ring, aromatic ring, or heteroaromatic ring, and can contain 0-3 heteroatoms selected from N, O, or S, and any hydrogen atom on the ring Q2 can be substituted by deuterium, hydroxy, halogen, cyano, ester, amide, ketocarbonyl, amino, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 thioalkyl, C1-C6 alkoxy, C1-C6 heteroalkyl, C1-C6 alkylamino, C3-C6 cycloalkyl, C3-C8 cycloalkylamino, aryl, or heteroaryl.