The impact of biomolecule interactions on the cytotoxic effects of rhenium(I) tricarbonyl complexes

Rhenium complexes show great promise as anticancer drug candidates. Specifically, compounds with a Re(CO)₃(NN)(py)⁺ core in their architecture have shown cytotoxicity equal to or greater than that of well-established anticancer drugs based on platinum or organic molecules. This study aimed to evaluate how the strength of the interaction between rhenium(I) tricarbonyl complexes fac-[Re(CO)₃(NN)(py)]⁺, NN = 1,10-phenanthroline (phen), dipyrido[3,2-f:2′,3′-h]quinoxaline (dpq) or dipyrido[3,2-a:2′3’-c]phenazine (dppz) and biomolecules (protein, lipid and DNA) impacted the corresponding cytotoxic effect in cells. Results showed that fac-[Re(CO)₃(dppz)(py)]⁺ has higher Log P_o/w and binding constant (K_b) with biomolecules (protein, lipid and DNA) compared to complexes of fac-[Re(CO)₃(phen)(py)]⁺ and fac-[Re(CO)₃(dpq)(py)]⁺. As consequence, fac-[Re(CO)₃(dppz)(py)]⁺ exhibited the highest cytotoxicity (IC₅₀ = 8.5 μM for HeLa cells) for fac-[Re(CO)₃(dppz)(py)]⁺ among the studied compounds (IC₅₀ > 15 μM). This highest cytotoxicity of fac-[Re(CO)₃(dppz)(py)]⁺ are probably related to its lipophilicity, higher permeation of the lipid bilayers of cells, and a more potent interaction of the dppz ligand with biomolecules (protein and DNA). Our findings open novel avenues for rational drug design and highlight the importance of considering the chemical structures of rhenium complexes that strongly interact with biomolecules (proteins, lipids, and DNA).