Design, synthesis and biological evaluation of bis-aryl ureas and amides based on 2-amino-3-purinylpyridine scaffold as DFG-out B-Raf kinase inhibitors

•Compound 6a was designed by combining the scaffolds of UI-125 and Sorafenib.•SAR was explored from the 2-amino-3-purinylpyridine derivatives.•All compounds have B-RafV600E inhibitory activities at nanomolar ranges.•Some compounds showed potent antiproliferation against melanoma A375 cell line.•Compound 20g displayed promising antitumor efficacy in vivo.

By combining the scaffolds of UI-125 and Sorafenib, a series of bis-aryl ureas and amides based on 2-amino-3-purinylpyridine moiety were designed and synthesized as novel DFG-out B-RafV600E inhibitors. Among them, 20c–e, 20g and 21h displayed potent antiproliferative activities against melanoma A375 (B-RafV600E) cell lines with IC50 values of 3.190, 2.276, 1.856, 1.632 μM and 1.839 μM, respectively, comparable with the positive control Vemurafenib (IC50 = 3.32 μM). Selected compounds were tested for the ERK inhibition in human melanoma A375 (B-RafV600E) and SK-MEL-2 (B-RafWT) cell lines by Western blot. The results revealed that our compounds inhibited the proliferation of melanoma A375 cells (B-RafV600E) through ERK pathway, without paradoxical activation of ERK in melanoma SK-MEL-2 cells (B-RafWT). Eventually, 20g and 21h were selected to confirm their inhibitory effects on tumor growth in A375 xenograft models in mice. Compound 20g exhibited equivalent antitumor efficacy in vivo (T/C = 44.37%), compared to Sorafenib (T/C = 37.35%), by 23-day repetitive administration of a single dose of 50 mg/kg without significant body weight loss.

Graphical abstractA series of 2-amino-3-purinylpyridine derivatives were synthesized and screened against B-RafV600E and A375 cell line, leading to the discovery of compound 20g, which exhibited potent A375 antiproliferative effects in vivo.Figure optionsDownload full-size imageDownload as PowerPoint slide