Phase I study of the novel taxane CT-2103 in patients with advanced solid tumors

CT-2103 (Cell Therapeutics, Seattle, Wash.) is a water-soluble macromolecular conjugate of paclitaxel to a polyglutamate backbone, designed to enhance tumor permeability and to improve intratumoral delivery of paclitaxel. Preclinical studies indicate that CT-2103 has substantial antitumor efficacy in xenograft tumor models.

We performed a phase I trial in patients with advanced solid tumors to determine the maximum tolerated doses (MTD) of CT-2103 when administered as short intravenous infusion every 3 weeks.

Seven patients received a total of 16 cycles (range 1-3) of CT-2103 at doses of 235 and 270 mg/m(2). Two of five patients treated at 235 mg/m(2) and one of two patients treated at 270 mg/m(2) experienced grade 3/4 neutropenia. Four patients experienced a marked increase in PTT within 30 min of the start of infusion. Neuropathy was more severe than expected. Two patients developed grade 3 neuropathy that prompted a 50% dose reduction of CT-2103 and persisted for 8 months in one, and over a year in the other. Three patients experienced grade 1 or 2 neuropathy. Neurotoxicity was cumulative and prevented patients from receiving prolonged administration of CT-2103.

The unexpectedly high rate of cumulative toxicity observed in our study needs to be taken into consideration in future trials of CT-2103. Prior taxane use may not be a predictor of severe neurotoxicity.