Compounds of formula (I) and pharmaceutically acceptable salts thereof wherein R
1
, R
2
and R
3
represent various functional groups, and one of X
1
and X
2
is N and the other is NR
10
; and their use as pharmaceuticals.
Compounds of formula (I) and pharmaceutically acceptable salts thereof wherein R1, R2 and R3 represent various functional groups, and one of X1 and X2 is N and the other is NR10; and their use as pharmaceuticals.