Cdk2 inhibitor pyrazolopyrimidine compounds

A compound of formula (I):

• or a pharmaceutically acceptable salt, solvate or prodrug thereof,
• wherein:
• Y1 is N or CR1, and
• Y2 is N or CR2, or
• —Y1═Y2— is an optionally substituted, fused 5-membered or 6-membered ring B:
• Y3 is NR3 or CR3R3′;
• Y4 is N or CR4;
• R1 is H, (C1-5)alkyl, substituted (C1-5)alkyl, (C1-5)alkoxyl, substituted (C1-5)alkoxyl, haloalkyl, halogen, OH, or CN;
• R2 is H, (C1-5)alkyl, substituted (C1-5)alkyl, (C1-5)alkoxyl, substituted (C1-5)alkoxyl, haloalkyl, halogen, OH, or CN;
• R3 is selected from H, alkyl, carbocycle, heterocycle, aryl, heteroaryl, alkylene-carbocycle, alkylene-heterocycle, alkylene-aryl, alkylene-heteroaryl, and substituted versions thereof;
• and
• R3′ is H, or (C1-5)alkyl;
• R4 is H, (C1-5)alkyl, substituted (C1-5)alkyl, haloalkyl, halogen, or CN;
• R5 is
• wherein:
• A is a cyclic group selected from carbocyclyl, heterocyclyl, aryl, heteroaryl, and substituted versions thereof;
• Z is an optional hydrophilic group;
• L1 and L2 are optional linkers;
• and
• * represents the point of attachment of R5 to the nitrogen atom;
• and
• R6 is H, (C1-5)alkyl, substituted (C1-5)alkyl, (C1-5)alkoxyl, substituted (C1-5)alkoxyl, haloalkyl, halogen, OH, or CN.