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The voltage-gated potassium channel K V 1.3 has been recognized as a tumor marker and represents a promising new target for the discovery of new anticancer drugs. We designed a novel structural class of K V 1.3 inhibitors through structural optimization of benzamide-based hit compounds and structure-activity relationship studies. The potency and selectivity of the new K V 1.3 inhibitors were investigated using whole-cell patch- and voltage-clamp experiments. 2D and 3D cell models were used to determine antiproliferative activity. Structural optimization resulted in the most potent and selective K V 1.3 inhibitor 44 in the series with an IC 50 value of 470 nM in oocytes and 950 nM in Ltk - cells. K V 1.3 inhibitor 4 induced significant apoptosis in Colo-357 spheroids, while 14 , 37 , 43 , and 44 significantly inhibited Panc-1 proliferation.

(1) Background: The voltage-gated potassium channel K V 10.1 (Eag1) is considered a near- universal tumour marker and represents a promising new target for the discovery of novel anticancer drugs. (2) Methods: We utilized the ligand-based drug discovery methodology using 3D pharmacophore modelling and medicinal chemistry approaches to prepare a novel structural class of K V 10.1 inhibitors. Whole-cell patch clamp experiments were used to investigate potency, selectivity, kinetics and mode of inhibition. Anticancer activity was determined using 2D and 3D cell-based models. (3) Results: The virtual screening hit compound ZVS-08 discovered by 3D pharmacophore modelling exhibited an IC 50 value of 3.70 µM against K V 10.1 and inhibited the channel in a voltage-dependent manner consistent with the action of a gating modifier. Structural optimization resulted in the most potent K V 10.1 inhibitor of the series with an IC 50 value of 740 nM, which was potent on the MCF-7 cell line expressing high K V 10.1 levels and low hERG levels, induced significant apoptosis in tumour spheroids of Colo-357 cells and was not mutagenic. (4) Conclusions: Computational ligand-based drug design methods can be successful in the discovery of new potent K V 10.1 inhibitors. The main problem in the field of K V 10.1 inhibitors remains selectivity against the hERG channel, which needs to be addressed in the future also with target-based drug design methods.