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Keywords:

  • Chemotherapy;
  • Epothilones;
  • Microtubule-stabilizing agents

Background

The epothilones are microtubule-stabilizing agents with promising antitumor effect in refractory and metastatic tumors in humans. The toxicity profile is considered more favorable than in taxanes. The safety of epothilone B (patupilone) has not been evaluated in tumor-bearing dogs.

Objectives

To evaluate the inhibition of proliferation in canine tumor cells after patupilone treatment. To assess toxicity profile and maximally tolerated dose of patupilone in dogs with refractory tumors.

Animals

Twenty client-owned dogs with various malignancies.

Methods

Prospective clinical study. The inhibition of proliferation was assessed with a proliferation assay in vitro in canine hemangiosarcoma and lymphoma cell lines. Dogs received patupilone IV once a week for 2 treatments (= 1 treatment cycle). Dose was escalated with 3 dogs per cohort and 20% increments. Adverse effects were graded accor-ding to the VCOG-CTCAE v1.0.

Results

Both canine cell lines were sensitive to patupilone with approximately 50% decrease in proliferative activity at 0.2–1 nM. In vivo, dose-limiting adverse effects occurred at 3.3 mg/m2; main adverse effects were diarrhea, anorexia, vomiting, and nausea. Neither neutropenia nor peripheral neuropathy was observed. Maximally tolerated dose for 2 patupilone administrations once weekly IV is 2.76 mg/m2. Three per 11 dogs receiving more than 1 treatment cycle showed partial remission in the short period of observation.

Conclusions and Clinical Importance

Canine tumor cells show inhibition of proliferation to patupilone in vitro. Clinically, a dose of 2.76 mg/m2 IV is well tolerated in dogs with spontaneously occurring tumors.