 It forms two hydrogen bonds between the hinge and pyrralocarbazole subunit.Later, series of more selective c-Met inhibitors were designed, where an indolin-2-one core (encircled in figure 1) was present in several kinase inhibitors.SU-11274 was evolved by substitution at the 5-position of the indolinone and by adding a 3,5-dimethyl pyrrole group, PHA-665752 was evolved – a second-generation inhibitor with better potency and activity.