Effect of low-dose tumor necrosis factor-alpha in combination with STEALTH liposomal cisplatin (SPI-077) on soft-tissue- and osteosarcoma-bearing rats.

Cisplatin is a widely used agent for treatment of solid tumors, but its clinical utility is limited by toxicity. Preclinical studies have shown less acute toxicity when STEALTH liposomal cisplatin (SPI-077) is used, with antitumor effects equivalent to those of intravenously administered free cisplatin. We previously reported that systemic treatment with low-dose tumor necrosis factor-alpha (TNF) augments the activity of STEALTH liposomal doxorubicin (Doxil). In this study, we examined the effect of repeated systemic applications of low-dose TNF on the antitumor activity of SPI-077 in rats with soft-tissue sarcoma or osteosarcoma. Addition of TNF to SPI-077 treatment showed an improved tumor growth delay of the soft-tissue sarcoma. The combined SPI-077/TNF treatment resulted in a more prolonged antitumor activity, whereas free cisplatin showed a better tumor response, however with a rapid outgrowth a few days after the end of therapy. In the osteosarcoma, free cisplatin did not have an antitumor effect, but addition of TNF caused a clear tumor growth delay. SPI-077 alone resulted in a tumor growth delay, but combination with TNF had no additive effect. SPI-077 yielded less systemic toxicity than cisplatin. Depending on the type of tumor, the addition of TNF to SPI-077 results in a better tumor growth delay with a prolonged antitumor effect and, in combination with the reduced toxicity of SPI-077, this combination may be preferable to cisplatin.