The role that the mitochondrial isoforms of the voltage-gated potassium channel KV1.3 (mitoKV1.3) and the calcium-activated potassium channel SK3 (mitoSK3) play in the regulation of apoptosis positions them at the center of cancer cell survival and makes them highly attractive anticancer targets. A distinctive advantage of these targets is that the hyperpolarized mitochondrial membrane potential (ΔΨm) of cancer cells can be exploited to selectively accumulate inhibitors conjugated to a mitochondria-targeting moiety (MTM). However, the chemical space of mitoKV1.3 and mitoSK3 inhibitors has remained narrow and dominated by a few scaffolds. Among them, the best established psoralen-based conjugates are limited by poor aqueous solubility. The aim of this doctoral dissertation was to overcome these limitations by designing, synthesizing, and biologically evaluating novel mitoKV1.3 and mitoSK3 inhibitors with expanded chemical diversity and improved properties.
We established a new non-psoralene class of benzamide-TPP+ mitoKV1.3-targeting conjugates (cis-8 and cis-9), whose mitoKV1.3-dependent cytotoxicity was confirmed in KV1.3-knockout cells. Systematic exploration of the linker length, stereochemical configuration, and MTM identified cis-24 (containing 4-(OMe)3-TPP+) as a submicromolar lead acting through mitochondrial uncoupling and permeability transition pore opening, while replacement of TPP+ by 3,5-diphenylpyridinium afforded cis-7, an in vivo active lead that reduced tumor growth in a B16F10 mouse melanoma model. Using ligand-based virtual screening, we identified structurally novel KV1.3 inhibitor TVS-26 and converted it into a new class of mitochondria-targeted conjugates (7a and 14d). Finally, extending this strategy to SK3, we developed the first mitochondria-targeted SK3 inhibitors, which were markedly more potent in cancer cells than the inactive parent SK3 inhibitors.
Overall, we have demonstrated that our integrated approach, which combines medicinal chemistry, structure-activity relationship studies, ligand-based virtual screening, and pharmacological and mitochondrial profiling, can successfully expand the chemical space of mitochondria-targeted potassium channel inhibitors and overcome key challenges in this field. The doctoral dissertation has contributed to a deeper understanding of mitochondrial potassium channels as anticancer targets and has facilitated the identification of novel mitoKV1.3 and mitoSK3 inhibitors, providing a solid starting point for the further development of mitochondria-directed anticancer agents.
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