Substituted triazole and imidazole derivatives as gamma secretase modulators

A compound of formula (I)

• or a stereoisomeric form thereof, wherein
• R1 is C1-4alkyl;
• R2 is hydrogen;
• X is CH;
• A1 is CR3a;
• wherein R3a is C1-4alkyloxy optionally substituted with one or more halo substituents;
• A2 is N;
• A3 and A4 are each CH;
• Het1 is formula (a)
• R4a is hydrogen;
• Ar1;
• or C1-6alkyl optionally substituted with one or more halo substituents;
• wherein in the definition of R4a, Ar1 is phenyl optionally substituted with one or more substituents each independently selected from the group consisting of halo and C1-4alkyl optionally substituted with one or more halo substituents;
• R5a is Ar2;
• wherein
• Ar2 is phenyl optionally substituted with one or more substituents each independently selected from the group consisting of halo and C1-4alkyl optionally substituted with one or more halo substituents;
• La represents NR9
• p represents 1 or 2;
• and,
• R9 is hydrogen,
• or a pharmaceutically acceptable addition salt thereof.