N-(4-aminocyclohexyl)pyrimidine-4-carboxamide derivatives as CD38 inhibitors

A compound of formula (I):

• or a pharmaceutically acceptable salt, solvate or prodrug thereof, wherein:
• Het is a 5-membered heteroaryl group comprising two heteroatoms independently selected from N and S, wherein the 5-membered heteroaryl group may optionally be substituted with one or two substituents independently selected from C1-C3 alkyl, C1-C3 fluoroalkyl and C1-C3 hydroxyalkyl;
• X1 is CH or N, and X2 is CH or N, wherein at least one of X1 and X2 is N;
• L is a bond, CH2, CHMe, CMe2 or CO;
• R1 is C1-C4 alkyl, C3-C6 cycloalkyl, hydroxyl, —O—(C1-C4 alkyl), or —O—(C3-C6 cycloalkyl), each of which may optionally be fluoro-substituted;
• R2 is hydrogen, C1-C4 alkyl, C1-C4 fluoroalkyl, —CHO, —CO—(C1-C3 alkyl) or —CO—(C1-C3 fluoroalkyl);
• R3 is hydrogen or methyl;
• or
• R2 and R3, together with the nitrogen to which they are attached, form an azetidin-1-yl, pyrrolidin-1-yl or piperidin-1-yl group, each of which may optionally be fluoro-substituted.