The influence of different carbonate ligands on the hydrolytic stability and reduction of platinum(IV) prodrugs

Synthesis and characterization of thiocarbonato-linked platinum(IV) complexes

Herein we show the formation of new oxaliplatin-based platinum(IV) complexes by reaction with DSC-activated thiols via thiocarbonate linkage. Three model complexes based on aliphatic and aromatic thiols, as well as one complex with N-acetylcysteine as biologically active thiol were synthesized. This synthetic strategy affords the expansion of biologically active compounds other than those containing carboxylic, amine or hydroxy groups for coupling to the platinum(IV) center. The complexes were characterized by high-resolution mass spectrometry, NMR spectroscopy (¹H, ¹³C, ¹⁹⁵Pt) and elemental analysis. Their biological behavior was evaluated against two ovarian carcinoma cell lines and their cisplatin-resistant analogues. Remarkably, the platinum(IV) samples show modest in vitro cytotoxicity against A2780 cells and comparable effects against A2780cis cells. Two complexes in particular demonstrate improved activity against SKOV3cis cells. The reduction experiment of complex 8, investigated by UHPLC-HRMS, provides evidence of interesting platinum-species formed during reaction with ascorbic acid.

Cyclooxygenase-Inhibiting Platinum(IV) Prodrugs with Potent Anticancer Activity

Platinum(IV) prodrugs of the [Pt(PL)(AL)(COXi)(OH)]2+ type scaffold (where PL is 1,10-phenanthroline or 5,6-dimethyl-1,10-phenanthroline, AL is 1S,2S-diaminocyclohexane, and COXi is a COX inhibitor, either indomethacin or aspirin) were synthesised and characterised, and their biological activity was explored. MTT assays showed that these complexes exhibit outstanding activity against a range of cancer cell lines, and nanomolar activities were observed. The most potent complex, 4, exhibited a GI50 of 3 nM in the Du145 prostate cancer cell line and was observed to display a 1614-fold increased activity against the HT29 colon cancer cell line relative to cisplatin. ICP-MS studies showed a linear correlation between increased cellular accumulation of the complexes and increased cytotoxicity, while an enzyme immunoassay showed that 1 and 2 inhibited COX-2 at 14 and 1.4 µM, respectively, which is comparable to the inhibition exhibited by indomethacin. These results suggest that while the cytotoxicity of prodrugs 1-4 was influenced by cellular uptake, it was not entirely dependent on either COX inhibition or lipophilicity.