Low in vivo toxicity of a novel cisplatin-ursodeoxycholic derivative (Bamet-UD2) with enhanced cytostatic activity versus liver tumors.

Cisplatin-bile acid derivatives belonging to the Bamet-family maintain both liver organotropism and cytostatic activity. "In vivo" toxicity and usefulness as chemotherapeutic agent versus liver tumors of a novel drug, Bamet-UD2 [cis-diamminechlorocholylglycinate platinum (II)], with enhanced "in vitro" cytostatic activity was investigated. Using orthotopically implanted mouse Hepa 1-6 hepatoma in the liver of Nude mice, the antitumor effect of Bamet-UD2 was compared with that of a previously characterized compound of this family, Bamet-R2 [cis-diamminebis-ursodeoxycholate platinum(II)], and cisplatin. Life span was significantly prolonged in mice treated with both Bamets (Bamet-UD2 > Bamet-R2), compared with animals receiving saline or cisplatin. All these drugs inhibit tumor growth (Bamet-UD2 = cisplatin > Bamet-R2). However, toxicity-related deaths only occurred under cisplatin treatment. Using rats maintained in metabolic cages, organ-specific toxicity and drug accumulation in tissues were investigated. The amount of both Bamets in the liver was severalfold higher than that of cisplatin. By contrast, a significantly higher amount of cisplatin in kidney and nerve was found. In lung, heart, muscle, brain, and bone marrow the amount of drug was small and also significantly lower in animals receiving Bamets. Signs of neurotoxicity (altered nerve conduction velocity), nephrotoxicity (increased serum urea and creatinine concentrations and decreased creatinine clearance), and bone marrow toxicity (decreased platelet and white blood counts) in animals treated with cisplatin but not with the Bamets were found. These results indicate that, owing to strong antitumor activity together with absence of side effects, Bamet-UD2 may be useful in the treatment of liver tumors.