Pixantrone (BBR 2778) has reduced cardiotoxic potential in mice pretreated with doxorubicin: comparative studies against doxorubicin and mitoxantrone.

Anthracyclines and anthracenediones are important oncotherapeutics; however, their use is associated with irreversible and cumulative cardiotoxicity. A novel aza-anthracenedione, pixantrone (BBR 2778), was developed to reduce treatment-related cardiotoxicity while retaining efficacy. This study evaluates the cumulative cardiotoxic potential of pixantrone compared with equiactive doses of doxorubicin and mitoxantrone in both doxorubicin-pretreated and doxorubicin-naïve mice. CD1 female mice were given doxorubicin 7.5 mg/kg (once weekly for 3 weeks) followed 6 weeks later by either sterile 0.9% saline, doxorubicin 7.5 mg/kg, pixantrone 27 mg/kg, or mitoxantrone 3 mg/kg (once weekly for 3 weeks). A second group of CD1 female mice were given 2 cycles of either sterile 0.9% saline, pixantrone 27 mg/kg, doxorubicin 7.5 mg/kg, or mitoxantrone 3 mg/kg (once weekly for 3 weeks). Animals were sacrificed at different time points for histopathologic examination of the heart. In the doxorubicin-pretreated mice, further exposure to doxorubicin or mitoxantrone resulted in a significant worsening of pre-existing degenerative cardiomyopathy. In contrast, pixantrone did not worsen pre-existing cardiomyopathy in these animals. Only minimal cardiac changes were observed in mice given repeated cycles of pixantrone, while 2 cycles of doxorubicin or mitoxantrone resulted in marked or severe degenerative cardiomyopathy. These animal studies demonstrate the reduced cardiotoxic potential of pixantrone compared with doxorubicin and mitoxantrone. Exposure to pixantrone did not worsen pre-existing cardiomyopathy in doxorubicin-pretreated mice, suggesting that pixantrone may be useful in patients pretreated with anthracyclines.

Identification of phenyl-pyridine-2-carboxylic acid derivatives as novel cell cycle inhibitors with increased selectivity for cancer cells.

Ro 41-4439, a phenyl-pyridine-2-carboxylic acid derivative, was identified by a cell-based screening approach that exploits the differences between normal and cancer cells in their sensitivity to cytotoxic agents. This compound showed low micromolar antiproliferative activity and cytotoxicity against a broad panel of human cancer cell lines in vitro, and over 10-fold selectivity to cancer cells when tested in parallel with a panel of proliferating normal human cells. Cytotoxicity of Ro 41-4439 is due to arrest of cell cycle progression in mitosis followed by induction of apoptosis. Four-week treatment of nude mice bearing established mammary tumor xenografts (MDA-MB-435) with well-tolerated doses of the compound showed 73% inhibition of tumor growth. Limited exploration of structure-activity relationships involving side chain length, and aryl and pyridine rings allowed for the identification of more potent analogs.