Acetylenehexacarbonyldicobalt complexes, a novel class of antitumor drugs

Acetylenehexacarbonyldicobalt complexes were synthesized and tested for antitumor activity. The MCF-7 and MDA-MB-231 mammary tumor cell lines and the LNCaP/FGC prostate carcinoma cell line were used as in vitro models. The structural evaluation was performed by IR and NMR spectroscopy and revealed a change of the linear acetylene core to a structure comparable to Z-olefins after coordination to the cobalt centers. In cell culture experiments the strongest effects were found for hexacarbonyl[2-propinylacetylsalicylate]dicobalt (10), which was more active than cisplatin on the human mammary tumor cell lines MCF-7 and MDA-MB-231 in each concentration tested (a 5 μM concentration of this compound even caused cytocidal effects). In contrast to this, 10 influenced the growth of the LNCaP/FGC cells only marginally, even in the highest concentration. The mode of action of the complexes tested is unknown. As the cobalt complexes show strong antiproliferative effects and their ligands do not it could be unambiguously demonstrated that complex formation is essential to achieve cytotoxic effects.