DNA double strand-breaks (DSBs) are the most deleterious lesions that can affect the genome of living beings and are lethal if not quickly and properly repaired. Recently, we discovered a new family of anticancer agents designated as N-phenyl ureidobenzenesulfonates (PUB-SOs) that are blocking the cells cycle progression in S-phase and inducing DNA DSBs. Previously, we have studied the effect of several modifications on the molecular scaffold of PUB-SOs on their cytocidal properties. However, the effect of the nature and the position of substituents on the aromatic ring B is still poorly studied. In this study, we report the preparation and the biological evaluation of 45 new PUB-SO derivatives substituted by alkyl, alkoxy, halogen and nitro groups at different positions on the aromatic ring B. All PUB-SOs were active in the submicromolar to low micromolar range (0.24-20 μM). The cell cycle progression analysis showed that PUB-SOs substituted at position 2 by alkyl, halogen or nitro groups or substituted at position 4 by a hydroxyl group arrest the cell cycle progression in S-phase. Interestingly, all others PUB-SOs substituted at positions 3 and 4 arrested the cell cycle in G2/M-phase. PUB-SOs arresting the cell cycle progression in S-phase also induced the phosphorylation of H2AX (γH2AX) which is indicating the generation of DNA DSBs. We evidenced that few modifications on the ring B of PUB-SOs scaffold lead to cytocidal derivatives arresting the cell cycle in S-phase and inducing γH2AX and DSBs. In addition, this study shows that these new anticancer agents are promising and could be used as alternative to circumvent some of the biopharmaceutical complications that might be encountered during the development of PUB-SOs.

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Combretastatin A-4 (CA-4) is a well-studied and attractive molecular template to develop new antimitotics. Several thousand of modifications were performed on the ring B and the ethenyl bridge of CA-4 but only a few involved the trimethoxyphenyl moiety (TMP, ring A) often considered essential to the antiproliferative and antimicrotubule activities. In this study, we described the design, the preparation, the characterization and the biological evaluation of three new series of CA-4 analogs namely styryl-N-phenyl-N'-ethylureas (SEUs), styryl-N-phenyl-N'-(2-chloroethyl)ureas (SCEUs) and styrylphenylimidazolidin-2-ones (SIMZs) bearing a 3-Cl (series a), 3,5-Me (series b) and TMP (series c) substituents, respectively. All SCEU and SIMZ Z-isomers were active in the high and the low nanomolar range, respectively. Conversely to SEUs and their E-isomers that were significantly less active or inactive. Interestingly, the TMP moiety is giving rise to derivatives exhibiting the lowest antiproliferative activity in the SCEU series (10c) and the most active compound in the SIMZ series (12c). Moreover, SIMZ Z-isomers bearing either a 3-Cl (12a) or a 3,5-Me (12b) exhibited antiproliferative activities that are also in the same order of magnitude as 12c. All SCEU and SIMZ Z-isomers also arrested the cell cycle progression in G2/M phase, bound to the colchicine-binding site and disrupted the cytoskeleton of cancer cells. In addition to the promising and innovative microtubule-disrupting properties of SCEUs and SIMZs, these results show that the TMP moiety is not essential for the cytocidal activity of these new CA-4 analogs.