A compound of the formula (I):
wherein:
A and B together represent an optionally substituted, fused aromatic ring;
X is selected from H and F;
R
1
and R
2
are independently selected from H and methyl;
R
N1
is selected from H and optionally substituted C
1-7
alkyl;
R
N2
is selected from H, optionally substituted C
1-7
alkyl, C
3-7
heterocyclyl and C
5-6
aryl;
or R
N1
and R
N2
and the nitrogen atom to which they are bound form an optionally substituted nitrogen containing C
5-7
heterocyclic group.