Fused heteroaryl derivatives

A fused heteroaryl compound of formula (Ib):

• or a salt thereof, wherein:
• B is a pyridine ring;
• R2 and R3 are combined together with the N atom adjacent thereto to form —NR2R3 which is a nitrogen-containing saturated heterocyclic group which may have one or two substituents selected from the group consisting of —OH, ═O and -a lower alkyl;
• R4b is —an aryl which has one to five substituents selected from Group A4;
• wherein Group A4 is selected from the group consisting of -a lower alkylene-OR, —CONRR′, —NR—CO-Cyc1, —NR—SO2-Cyc1, —OR, —NRR′, —O-a lower alkylene-NRR′ and —O-a lower alkylene-(a nitrogen-containing saturated ring which may have one to five substituents selected from Group A), wherein Cyc1, is —an aryl which may have one to five substituents selected from Group A, -a heteroaryl which may have one to five substituents selected from Group A, or -a nitrogen-containing saturated heterocyclic group which may have one to five substituents selected from Group A;
• wherein Group A is selected from the group consisting 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 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″, may be the same or different and are independently selected from the group consisting of H or a lower alkyl.