A compound of formula I: ** Formula ** or a pharmaceutically acceptable salt or ester thereof, in which: X is NRNRN ', GOLD, SRS or ** Formula ** in which ** Formula ** is attached to the imidazopyridinyl ring of formula I in the position indicated by "**"； RO and RS are each independently C6-C10 aryl unsubstituted or substituted； RN is (CH2) mRhc or C6-C10 aryl unsubstituted or substituted； RN 'is H； or RN and RN ', together with the nitrogen atom to which they are attached, form an unsubstituted or substituted morpholine； m is 1, 2, 3 or 4； Rhc is an unsubstituted or substituted heterocycle comprising a 6-membered ring and 1 or 2 heteroatoms selected from N, O and S； and Rph is substituted C3-C6 alkyl or unsubstituted C4-C6 alkyl； wherein: said substituted aryl and substituted heterocycle are substituted at one or more positions of the ring with alkyl, alkenyl, alkynyl, halogen, hydroxy, alkoxy, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, alkylaminocarbonylaminocarbonylaminocarbonylaminocarbonylaminocarbonylaminocarbonylamino alkylcarbonyl, arylcarbonyl, aralkylcarbonyl, alkenylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, phosphate, phosphonate, phosphinate, amino (including alkylamino, dialkylamino, arylamino, diarylamino and alkylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, imylcarbonylamino, amylcarbonylamino, imylcarbonylamino, imylcarbonylamino, amylaminocarbonylamino sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, alkylsulfinyl, sulfonate, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl or an aromatic or heteroaromatic moiety； said substituted morpholine is substituted with one or more groups, each of which is independently selected from hydroxyl, halogen (including fluorine, chlorine, bromine and iodine), cyano, nitro, unsubstituted amino, C1-C6 alkylamino, di-alkylamino C1-C6 unsubstituted or substituted, C1-C6 a
