Intravenous administration of 9-aminocamptothecin to dogs with lymphoma

A colloidal dispersion formulation of 9-aminocamptothecin (9-AC) was administered intravenously to 10 dogs with previously untreated, spontaneously occurring, multicentric lymphoma. The dogs received a 72-h infusion of 9-AC at a rate of 46.5-51.25 microg m(-2) h(-1) (total dose range 3.35-3.69 mg m(-2)). This dose range was associated with myelosuppression, consisting principally of neutropenia with a nadir at 7 days following the start of infusion. Neutropenia and thrombocytopenia were the most common toxicoses and are most likely to be dose-limiting toxicities; low-grade gastrointestinal signs were rarely seen. Concentrations of 9-AC lactone, as well as clinical toxicities, compare favourably with those found in humans. Tumour responses were seen in all treated dogs. Response to other chemotherapy, following cessation of 9-AC treatment, was not obviously compromised even in dogs clinically resistant to 9-AC. 9-AC is a novel treatment drug for canine lymphoma, which appears to show great promise.