New steroidal 7-azaindole platinum(II) antitumor complexes

•New steroidal Pt(II) conjugates were synthesized.•Steroidal platinum complexes overcome resistance to cisplatin.•The new Pt(II) compounds are able to interact with DNA.•The new Pt(II) steroidal conjugates are also good cathepsin B inhibitors.

Two new steroidal 7-azaindole-based N-donor ligands 17-α-[7-azaindole-5-ethynyl]-17-β-testosterone (ET-Haza) (1) and 17-α-[7-azaindole-5-ethynyl]-19-nortestosterone (LEV-Haza) (2), and two new DNA damaging warheads with an enhanced lipophilicity [Pt(dmba)Cl(L)] (dmba = N,N-dimethylbenzylamine-κN,κC; L = ET-Haza (3) and LEV-Haza (4)) have been prepared and characterized. Values of IC50 were calculated for complexes 3 and 4 against a panel of human tumor cell lines representative of ovarian (A2780 and A2780cis) and breast cancers (T47D). At 48 h of incubation time 3 and 4 showed very low resistance factors (RF of 1) against an A2780 cell line which has acquired resistance to cisplatin, IC50 values of the new complexes towards normal human LLC-PK1 renal cells at 48 h being about double than that of cisplatin. 3 and 4 are able to react with 9-ethylguanine (9-EtG) yielding the corresponding monoadduct [Pt(dmba)(L)(9-EtG)]+ derivatives as followed by ESI-MS. Compound 3 interacts mainly with double-stranded (DS) oligonucleotides as shown by analysis with ESI-TOF-MS, being also able to displace ethidium bromide (EB) from DNA, as observed by an electrophoretic mobility study. 3 and 4 are good cathepsin B inhibitors. Theoretical calculations at the COSMO(CHCl3)/B3LYP-D/def2-TZVPPecp//B3LYP-D/def2-TZVPecp level and energy evaluations at the COSMO(CHCl3)/PWPB95-D3/def2-TZVPPecp level of theory on compound 4 and model systems have been done.

Graphical abstractTwo novel antitumor steroidal 7-azaindole platinum(II) conjugates with DNA binding and an enhanced lipophilicity are described.Figure optionsDownload full-size imageDownload as PowerPoint slide