Metal (Au, Pt, Pd, Ni) Bis(dithiolene) complexes as dual-action agents combating cancer and trypanosomatid infections

Cancer and infection diseases pose severe threats to public health worldwide stressing the need for more effective and efficient treatments. Thus, the search for broad-spectrum activity drugs seems justifiable and urgent. Herein, we investigate the anticancer and antitrypanosomatid (anti-Trypanosoma cruzi) activities of eight monoanionic metal bis(dithiolene) complexes, [Ph₄P][M(R-thiazdt)₂] with Mⁿ⁺ = Au³⁺, Pt²⁺, Pd²⁺, Ni²⁺, containing N-alkyl-1,3-thiazoline-2-thione dithiolene ligands (R-thiazdt) with different alkyl groups (R = Et, tBu). Compared to auranofin (AF) and cisplatin (CP), two reference drugs in clinical use, all complexes showed high anticancer activities against A2780 ovarian cancer cells (IC₅₀ values of 0.6-3.8 μM) some also being able to overcome CP resistance in A2780cisR cells. The selectivity index (SI), the IC₅₀ values on normal cells (HDF) vs. A2780 cells, indicated good anticancer specificity (SI > 3) for most of the complexes but with clinical relevance for [Ph₄P][Pd(tBu-thiazdt)₂] (SI = 10). All complexes showed relevant antitrypanosomatid activities (IC₅₀ values of 2.6-5.8 μM) some even exhibiting lower IC₅₀ values than the reference drug nifurtimox (NFX). The mechanism of cell death seemed to be mediated mainly by the formation of reactive oxygen species (ROS), although to lesser extent for the gold complexes but superior to AF. Although ROS play a role in the main apoptotic pathways, cell death by apoptosis was not evident as shown by the caspase-3/7 assay and the morphological cell features studies by electron microscopy (SEM). Results obtained evidenced that [Ph₄P][Pt(tBu-thiazdt)₂] and [Ph₄P][Pd(tBu-thiazdt)₂] complexes might have potential as novel anticancer and antitrypanosomatid agents as alternatives to current therapeutics.