Fused heteroaryl derivatives

A fused heteroaryl compound of formula (Ia):

• or a salt thereof, wherein:
• R2 and R3, which may be the same or different, are independently —H or -a lower alkyl, or R2 and R3 are combined together with the N atom adjacent thereto to form a nitrogen-containing saturated heterocyclic group as —NR2R3 which may have 1 or 2 substituents selected from the group comprising of —OH, ═O and -a lower alkyl;
• X is N;
• Y is O, S or NH;
• R41 is -(an aryl which may have one to 5 substituents selected from Group A4), -a lower alkylene-(an aryl which may have one to 5 substituents selected from Group A4), -a lower alkenylene-(an aryl which may have one to 5 substituents selected from Group A4), -a lower alkynylene-(an aryl which may have one to 5 substituents selected from Group A4), -(a cycloalkyl which may have one to 5 substituents selected from Group A), -(a cycloalkenyl which may have one to 5 substituents selected from Group A), -a lower alkylene-(a cycloalkyl which may have one to 5 substituents selected from Group A), -a lower alkenylene-(a cycloalkyl which may have one to 5 substituents selected from Group A), -a lower alkylene-(a nitrogen-containing saturated heterocyclic group which may have one to 5 substituents selected from Group A), -a lower alkenylene-(a nitrogen-containing saturated heterocyclic group which may have one to 5 substituents selected from Group A), -(a heteroaryl which may have one to 5 substituents selected from Group A4), -a lower alkylene-(a heteroaryl which may have one to 5 substituents selected from Group A4), or -a lower alkenylene-(a heteroaryl which may have one to 5 substituents selected from Group A4);
• and
• Group A consists of -a lower alkyl, -a lower alkenyl, -a lower alkynyl, -a halogen, -a halogenated lower alkyl, -a lower alkylene-OR, —NO2, —CN, ═O, —OR, —O-a halogenated lower alkyl, —O-a lower alkylene-NRR′, —O-a lower alkylene-OR, —O-a lower alkylene-an aryl, —SR, —SO2-a lower alkyl, —SO-a lower alkyl, —COOR, —COO-a lower alkylene-an aryl, —COR, —CO-an aryl, -an aryl, —CONRR′, —SO2NRR′, —NRR′, —NR″-a lower alkylene-NRR′, —NR′-a lower alkylene-OR, —NR-a lower alkylene-an aryl, —NRCO-a lower alkyl, —NRSO2-a lower alkyl, -a cycloalkyl and -a cycloalkenyl;
• and wherein R, R′and R″, which may be the same or different, represent H or a lower alkyl;
• Group A4 consists of
• a) -a lower alkyl, -a lower alkenyl, -a lower alkynyl, -a halogen, -a halogenated lower alkyl, -a lower alkylene-OR, —NO2, —CN, ═O, —O-halogenated lower alkyl, —SO2-a lower alkyl, —SO-a lower alkyl, —COOR, —COO-a lower alkylene-an aryl, —COR, —CO-an aryl, —CONRR′, —SO2NRR′, -Cyc or -Alp-Cyc (wherein Alp is a lower alkylene, a lower alkenylene or a lower alkynylene, and Cyc is an aryl which may have 1 to 5 substituents selected from Group A, a heteroaryl which may have 1 to 5 substituents selected from Group A, a nitrogen-containing saturated heterocyclic group which may have 1 to 5 substituents selected from Group A, a cycloalkyl which may have 1 to 5 substituents selected from Group A, or a cycloalkenyl which may have 1 to 5 substituents selected from Group A;
• b) —NR-E-F (wherein B is —CO—, —COO—, —CONR′—, —SO2NR′— or —SO2—;
• F is -Cyc or -(a lower alkyl, a lower alkenyl or a lower alkynyl which may be substituted by one or more substituents selected from the group comprising of -a halogen, —NO2, —CN, —OR, —O- a lower alkylene-NRR′, —O-a lower alkylene-OR, —SR, —SO2-a lower alkyl, —SO-a lower alkyl, —COOR, —COR, —CO-an aryl, —CONRR′, —SO2NRR′, —NRCO-a lower alkyl, —NRR′, —NR′-a lower alkylene-OR, —NR″-a lower alkylene-NRR′ and -Cyc), and
• c) —Z—R′, —Z-Cyc, —Z-Alp-Cyc, —Z-Alp-Z′—R′ or —Z-Alp—Z′-Cyc (wherein each of Z and Z′, which may be the same or different, are independently O, S or NR.