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.