Nitrogen substituted 1,2,4-triazolo[3,4-a]phthalazine derivatives for enhancing cognition

The present invention provides a compound of formula (I) wherein A is an optionally substituted C_1-4alkylidene group or a bond, R²⁰ and R²¹ are hydrogen, alkyl groups or heterocyclic groups, R¹ and R² are small substituents or hydrogen, L is O, S or substituted N, X is a 5- or 6-membered heteroaromatic ring, Y is C_1-4alkylidene and Z is a 5- or 6-membered heteroaromatic ring; or a pharmaceutically acceptable salt thereof; pharmaceutical compositions comprising it; its use in therapy; its use in making medicaments for treating neurodegenerative disease and methods of using it to enhance cognition.