First-in-human phase 0 trial of oral 5-iodo-2-pyrimidinone-2′- deoxyribose in patients with advanced malignancies

Purpose: Iododeoxyuridine (IdUrd), a halogenated nucleoside analog, produced clinical responses when administered as a radiosensitizer via continuous intravenous (c.i.v.) infusion over the course of radiotherapy. We conducted a phase 0 trial of 5-iodo-2-pyrimidinone-2′-deoxyribose (IPdR), an oral prodrug of IdUrd, in patients with advanced malignancies to assess whether the oral route was a feasible alternative to c.i.v. infusion before embarking on large-scale clinical trials. Plasma concentrations of IPdR, IdUrd, and other metabolites were measured after a single oral dose of IPdR. Experimental Design: Eligible patients had advanced refractory malignancies. A single oral dose of IPdR was administered per patient and patients were followed for 14 days for safety assessments; dose escalations were planned (150, 300, 600, 1,200, and 2,400 mg) with one patient per dose level and 6 patients at the highest dose level. Blood sampling was conducted over a 24-hour period for pharmacokinetic analysis. Results: There were no drug-related adverse events. Plasma concentrations of IdUrd generally increased as the dose of IPdR escalated from 150 to 2,400 mg. All patients at the 2,400 mg dose achieved peak IdUrd levels of (mean ± SD) 4.0 μmol/L ± 1.02 mmol/ L at 1.67 ± 1.21 hours after IPdR administration. Conclusions: Adequate plasma levels of IdUrd were obtained to justify proceeding with a phase I trial of IPdR in combination with radiation. This trial shows the ability of a small, phase 0 study to provide critical information for decision-making regarding future development of a drug.