Compounds and their use in treating cancer

A compound of Formula (I):

• or a pharmaceutically acceptable salt or prodrug thereof, wherein:
• R1 represents H or methyl;
• A and G are independently CR2 or N;
• R2 is independently selected from H, F, Cl, CN, methyl or methoxy;
• D and E are independently CR3 or N;
• R3 is independently selected from H, F, Cl, or methyl;
• R4 represents H, methyl or F;
• R5 represents H, methyl or F;
• or R4 and R5 taken together with the carbon atom to which they are attached form a cyclopropyl ring or an oxetanyl ring;
• R6 represents H, methyl, F, CH2F, CHF2, CF3, CN, CH2CN, CH2OMe, CH2OH, C(O)OH, C(O)OMe or SO2Me;
• R7 represents H, methyl, —CH2NHMe, —CH2NMe2 or CH2NH2;
• X represents —O—, —CH═CH—C(O)NH—, —NHC(O)—, —C(O)NH— or -pyrrolidinyl-NMeC(O)—;
• Y represents a bond or —C(O)—;
• and
• Linker is an optionally substituted linking moiety comprising a branched or unbranched, cyclized or uncyclized, saturated or unsaturated chain of 4 to 20 carbon atoms in length, wherein 1 to 6 of the carbon atoms are optionally replaced with a heteroatom independently selected from O, N and S.