A phase I study of T900607 given once every 3 weeks in patients with advanced refractory cancers; National Cancer Institute of Canada Clinical Trials Group (NCIC-CTG) IND 130

Background: T900607 is a novel tubulin active agent which disrupts microtubule polymerization by a unique mechanism of action. This phase I trial was conducted to determine the maximum tolerated dose, recommended phase II dose, pharmacokinetic properties and toxicities of this agent. Patients and methods: Patients with advanced and/or metastatic solid malignancies were enrolled, for an open dose escalation of T900607 administered intravenously over 30 minutes every 21-days. Results: Thirty patients were enrolled on 7 dose levels ranging from 15 to 270 mg/m(2). No DLTs were seen until 270 mg/m(2), the sixth dose level, with 1 patient experiencing Grade 3 thrombocytopenia, 1 grade 4 troponin increase and 1 grade 5 myocardial infarction in an expanded cohort of 6 patients. The dose was decreased to 180 mg/m(2) with increased cardiac monitoring and at this dose 3/4 patients experienced cardiac toxicity. Further animal cardiotoxicity studies failed to reveal any cardiac effects and the study was reopened at 130 mg/m(2); of 6 enrolled patients, 1 had grade 3 drug related lethargy considered to be a DLT and this dose was considered the RP2D. No objective responses were seen but stable disease was reported in 7/20. Pharmacokinetic analysis showed that AUC and C-max increased with dose with considerable intrapatient variability, a short half life of< 1 hour, and no apparent dose dependency clearance. Conclusions: The recommended phase II dose for T900607 is 130 mg/m(2) given as an intravenous infusion over 60 minutes on a 21-day cycle. Cardiac toxicity was seen with this schedule.