Anticancer activity in murine and human tumor cell lines of bis(platinum) complexes incorporating straight-chain aliphatic diamine linker groups.

The biological activity of a series of dinuclear bis(platinum) complexes of formula [(cis-PtX2-(NH3)]2(NH2(CH2)nNH2)] (X = Cl, n = 4-9, compounds 6-11; X2 = malonate, n = 5 or 6, compounds 12 and 13) is described in selected murine leukemia, murine solid tumor, and human tumor cell lines and in murine leukemia cell lines rendered resistant to cisplatin (cis-[Pt(NH3)2Cl2]). The bis(platinum) compounds showed greater activity in vitro against murine tumor cell lines resistant to either cisplatin or DACH ([Pt(DACH)Cl2]). The resistance factor is dependent on chain length of the diamine, and the structural feature of a dinuclear complex is of general use in reducing cross-resistance with cisplatin. In vivo [(cis-PtCl2(NH3)]2(NH2(CH2)5NH2)] (7) showed a % T/C of 204 against murine L1210 leukemia resistant to cisplatin compared to a % T/C of 104 for cisplatin itself at optimal doses. The complex [(Pt(mal)(NH3)]2(NH2(CH2)6NH2)] (13) was highly active in the colon 26 tumor line with 3/10 tumor-free survivors (dose of 186 mg/kg, ip D1,5,9); however, 13 was subject to substantial cross-resistance in the cisplatin resistant L1210 leukemia (% T/C 139 versus % T/C of 223 in the sensitive line). In four selected human tumor lines in vitro, compounds 6-11 were uniformly more potent than cisplatin. In the corresponding xenografts, compound 7 showed greater activity in the HCT-8 (coloadenocarcinoma) and H23 (nonsmall cell lung), but diminished potency in AH125 and H520 (both nonsmall cell lung) lines in comparison to cisplatin. Retention of activity against cisplatin-resistant cell lines and a different spectrum of activity compared to cisplatin in some human tumor cell lines suggest that this class of complexes is mechanistically different from mononuclear complexes and worthy of further development toward clinical trials.