Voltage-gated potassium channels 1.3 (KV1.3) are involved in numerous pathological conditions, including autoimmune diseases, chronic inflammation and cancer. Mitochondrial channels KV1.3 are especially important in regulating the intrinsic pathway of apoptosis in cancer cells. Mitochondrial KV1.3 can be considered as an important target in the future therapy of cancer, because of their overexpression in multiple types of tumours. Small organic molecules with attached mitochondria-targeting moieties, such as pyridinium and triphenylphosphonium ions, that inhibit mitochondrial KV1.3, can cause apoptosis of cancer cells and therefore stop the progression of the disease.
In the master's thesis we designed and synthesized new inhibitors based on the structure of the already developed benzamide-based mitochondrial KV1.3 inhibitors PSG-369 and PSG-373. We included the benzamide moiety and the carbamate group, but we changed the configuration, the length of the spacer and the structure of the transport groups. The synthesis consisted of two or three steps, in which we used the mechanism of nucleophilic SN2 substitution. For the synthesis of compound 20, we first converted the carbonate bond to the carbamate group. Then, as for all the other compounds, we changed the alcohol group to iodide using the Appel reaction. Lastly, the final step of the synthesis was the addition of six different pyridinium and triphenylphosphonium mitochondria-targeting groups.
The synthesized compounds were biologically evaluated on human Ewing sarcoma cells SK-N-MC, human pancreas adenocarcinoma cells Colo-357 and normal human lung fibroblasts NHLF. Additionally, we determined LogD and thermodynamic solubility of the final compounds. The most polar compounds with pyridinium and 3,5-dimethylpyridinium ions did not show a cytotoxic effect on SK-N-MC cells. Compounds 3, 4, 5 and 11 with triphenylphosphonium cations and hexyl spacers had the most potent cytotoxic activity among all final compounds. These compounds also had higher values of LogD and were therefore more lipophilic, which resulted in better penetration into mitochondria. Compound 4 was the most potent, with a half-maximal inhibitory concentration of 0,50 ± 0,01 μM on SK-N-MC cells and 0,64 μM on Colo-357 cells. All compounds, tested on non-cancerous NHLF cells, showed cytotoxicity, which would suggest that they are not as safe and do not act selectively on cancer cells. Based on the results obtained, we can conclude that it would be necessary in further research to optimize the structure of the inhibitors and thus reduce their toxicity.
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