A Comprehensive <i>In Vitro</i> Characterization of a New Class of Indole-Based Compounds Developed as Selective Haspin Inhibitors

Haspin is an emerging, but rather unexplored, divergent kinase involved in tumor growth by regulating the mitotic phase. In this paper, the <i>in-silico</i> design, synthesis, and biological characterization of a new series of substituted indoles acting as potent Haspin inhibitors are reported. The synthesized derivatives have been evaluated by FRET analysis, showing very potent Haspin inhibition. Then, a comprehensive in-cell investigation highlighted compounds <b>47</b> and <b>60</b> as the most promising inhibitors. These compounds were challenged for their synergic activity with paclitaxel in 2D and 3D cellular models, demonstrating a twofold improvement of the paclitaxel antitumor activity. Compound <b>60</b> also showed remarkable selectivity when tested in a panel of 70 diverse kinases. Finally, <i>in-silico</i> studies provided new insight about the chemical requirements useful to develop new Haspin inhibitors. Biological results, together with the drug-likeness profile of <b>47</b> and <b>60</b>, make these derivatives deserving further studies.