Imidazopyridine-fused [1,3]diazepinones: modulations of positions 2 to 4 and their impacts on the anti-melanoma activity

A series of 19 novel pyrido-imidazodiazepinones, with modulations of positions 2, 3 and 4 of the diazepine ring were synthesised and screened for their in vitro cytotoxic activities against two melanoma cell lines (A375 and MDA-MB-435) and for their potential toxicity against NIH-3T3 non-cancerous cells. Selected compounds were also evaluated on the NCI-60 cell line panel. The SAR study revealed that the molecular volume and the cLogP of compounds modified at position 2 were significantly correlated with the activity of these compounds on melanoma cell lines. Moreover, introduction of a heterocyclic group at position 2 or an azido-alkyl chain at position 4 led to compounds displaying a significantly different activity profile on the NCI-60 cell line panel, compared to phenyl-substituted compounds at position 2 of the diazepinone. This study provides us crucial information for the development of new derivatives active against melanoma.