Novel N-phenyl-2-(aniline) benzamide hydrochloride salt development for colon cancer therapy.

Introduction: N-phenyl-2-(aniline) analog N53 is a previously discovered dual inhibitor of Topo I and COX-2, which exhibited significant anti-colon cancer activity in vitro, but the poor solubility and moderate anti-cancer activity in vivo hindered its further development.

Methods: To rectify the suboptimal drug properties of N53, a series of salt forms were developed and further evaluated through in vivo and in vitro experiments.

Results: The hydrochloride (N53·HCl) has a well-characterized crystal structure and its solubility reached 540.1 μg/mL, which is nearly 1,700 times higher than that of N53 (0.32 μg/mL). Increasing the N53 solubility consistently promotes its effective concentration, further enhancing the COX-2/Topo I inhibitory activity and the anti-tumor activity in vitro (IC₅₀ values of 2.95 ± 0.08 μM for HT29 cells, 7.99 ± 0.85 μM for RKO cells, 10.94 ± 1.30 μM for HCT116 cells), as well as the anti-proliferative and pro-apoptotic activity. Meanwhile, its oral pharmacokinetic property in vivo is also improved. The elimination half-life (T1/2) is prolonged from 10.78 to 22.29 h, the maximum plasma concentration (C_max) is increased 2-fold, and the area under the plasma drug concentration-time curve (AUC_0-∞) is increased 3-fold. In colon cancer xenograft mouse models, the tumor inhibition rate of N53·HCl was 53.7%, superior to that of N53 (34.7%). Moreover, the results of HE staining showed that N53·HCl had no obvious toxic effects and side effects on other organs, indicating that it was safe in vivo.

Discussion: This study demonstrated that N53·HCl exhibits superior pharmacokinetic properties, anti-colon cancer efficacy, and safety, providing a promising drug candidate for colon cancer therapy.