Safety evaluation of combination vinblastine and toceranib phosphate (Palladia®) in dogs: a phase I dose-finding study


  • Presented in abstract form at the 30th Annual Conference of the Veterinary Cancer Society, San Diego, CA, USA, October 2010.

D. M. Vail

School of Veterinary Medicine

University of Wisconsin-Madison

Madison, WI 53706, USA



Combining drugs with known single-agent activity that lack overlapping dose-limiting toxicities (DLT) and exert antitumour activity through different mechanisms could improve clinical outcome. As toceranib and vinblastine meet these requisites, a phase I trial was performed in combination in dogs with mast cell tumours. The DLT for the simultaneous combination was neutropenia and the maximally tolerated dose was vinblastine (1.6 mg m−2 every other week) concurrent with toceranib (3.25 mg kg−1 PO, every other day). This represents greater than a 50% reduction in dose intensity for vinblastine (compared with single-agent use) and as such does not support this combination based on current drug combination paradigms. Although a strict adherence to dose paradigms speaks against the combination, evidence of significant activity (71% objective response) and enhanced myelosuppression suggest additive or synergistic activity. A prospective randomized evaluation comparing this combination with standard single-agent treatments would seem prudent to interrogate this potential.