Sulphones which modulate the action of gamma secretase

A compound of formula I

• wherein
• Ar1 is selected from 4-chlorophenyl, 4-fluorophenyl, 4-trifluoromethylphenyl, 3,4-difluorophenyl, 3,4-dichlorophenyl and 4-methoxyphenyl;
• Ar2 is selected from 2,5-dichlorophenyl, 2,5-difluorophenyl and 2-hydroxymethyl-5-fluorophenyl;
• R1 represents H, or C1-6alkyl or C2-6alkenyl, any of which is optionally substituted by halogen, CN, NO2, CF3OH, C1-4alkoxy or C1-4alkoxycarbonyl;
• R2 represents a saturated or unsaturated hydrocarbon linking group of up to 6 carbon atoms;
• X represents —O—, —S—, —SO2—, —N(R4)—, —C(O)—, —OC(O)—, —C(O)O—, —C(O)N(R4)—, —N(R4)C(O)—, —OC(O)O—, —N(R4)C(O)O—, —OC(O)N(R4)—, —SO2N(R4)— or —N(R4)SO2—;
• R3 represents C1-10alkyl, C2-6alkenyl or C2-6alkynyl, any of which may be substituted by OR4;
• R4 represents H or C1-4alkyl
• m and n are each 0;
• or a pharmaceutically acceptable salt thereof.