Chemical compounds

A compound of formula (I):

• or a pharmaceutically acceptable salt thereof, wherein
• R1 is a ‘C-linked’ 6-membered heteroaryl containing one, two or three nitrogen atoms wherein said heteroaryl is optionally substituted by one, two or, three valency permitting, X1;
• each X1 is independently selected from:
• F;
• CI;
• CN;
• (C1-C4)alkyl optionally substituted by one, two or three F;
• or (C1-C4)alkyloxy optionally substituted by one two or three F;
• R2, R3 and R5 are independently selected from:
• H;
• halogen;
• CN;
• (C1-C4)alkyl optionally substituted by one, two or three F;
• or (C1-C4)alkyloxy optionally substituted by one, two or three F;
• R4 is selected from:
• halogen;
• CN;
• (C1-C4)alkyl optionally substituted by one, two or three F;
• or (C1-C4)alkyloxy optionally substituted by one, two or three F;
• R6 is phenyl substituted by one, two or three X2;
• or a ‘C-linked’ 6-membered heteroaryl containing one or two nitrogen atoms wherein said heteroaryl is optionally substituted by one, two or three X2;
• each X2 is independently selected from:
• F;
• CI;
• CN;
• —S(C1-C4)alkyl;
• —NR7R8;
• (C1-C6)alkyloxy optionally substituted by one, two or three F;
• (C3-C6)cycloalkyloxy;
• (C1-C6)alkyl optionally substituted by one, two or three F;
• or (C1-C6)alkyl substituted by OH;
• and
• R7 and R8 are independently H or (C1-C4)alkyl or, together with the nitrogen atom to which they are attached, form a saturated 4- to 6-membered nitrogen containing monocycle.