Heterocyclic inhibitors of atr kinase

A compound of structural Formula (I):

• or a salt thereof, wherein:
• R1 is a 4- to 10-membered heterocycloalkyl and is optionally substituted with one or more R4 groups;
• R2 is a 5- to 10-membered heteroaryl, and is optionally substituted with one or more R5 groups;
• R3 is selected from H, C1-6alkyl, and C1-6haloalkyl;
• each R4 is independently selected from halogen, cyano, hydroxy, alkyl, C3-7cycloalkyl, haloalkyl, hydroxyalkyl, (C3-7cycloalkyl)alkyl, (5- to 10-membered heterocycloalkyl)alkyl, (alkoxy)alkyl, alkoxy, haloalkoxy, hydroxyalkoxy, (C3-7cycloalkyl)alkoxy, (5- to 10-membered heterocycloalkyl)alkoxy, (alkoxy)alkoxy, C3-7cycloalkyl, C3-7halocycloalkyl, C3-7hydroxycycloalkyl, (alkoxy)C3-7cycloalkyl, 5- to 10-membered heterocycloalkyl, (halo)5- to 10-membered heterocycloalkyl, (hydroxy)5- to 10-membered heterocycloalkyl, (alkoxy)5- to 10-membered heterocycloalkyl, NR7R8, C(O)R6, C(O)OR6, C(O)NR7R8, NR7C(O)NR7R8, NR7C(O)OR6, NR7C(O)R6, S(O)R6, S(O)2R6, S(NR7)R8, S(O)(NR7)R8, SO2NR7R8, oxo, and ═NR10;
• each R5 is independently selected from amino, fluoro, chloro, cyano, C1-3alkyl, C1-3aminoalkyl, C1-3haloalkyl, C1-3alkoxy, C1-3hydroxyalkyl, C1-3haloalkoxy, C3-7cycloalkyl, and 5- to 10-membered heterocycloalkyl;
• each R6, R7, and R8 is independently selected from H, C1-3alkyl, C3-7cycloalkyl, C1-3hydroxyalkyl, (C1-3alkoxy)C1-3alkyl, (C3-7cycloalkyl)C1-3alkyl, and 5- to 10-membered heterocycloalkyl and is optionally substituted with one or more R9;
• R7 and R8, together with the nitrogen to which they are both attached, optionally form a 5- to 10-membered heterocycloalkyl ring containing one or two heteroatoms;
• each R6, R7, or R8 can form a ring with R4;
• each R9 is independently selected from halo, hydroxy, C1-3alkyl, C1-3haloalkyl, C3-7cycloalkyl, 5- to 10-membered heterocycloalkyl, and C1-3alkoxy;
• and
• each R10 is independently selected from H, C1-3alkyl, C1-3alkoxy, C1-3haloalkyl, C3-7cycloalkyl, and 5- to 10-membered heterocycloalkyl.