Deflexifol (a novel formulation of 5FU): Phase 1 dose escalation study of infusional and bolus schedules after failure of standard treatment.
2529 Background: 5-Fluorouracil (5FU) is administered in combination with leucovorin (LV) to enhance clinical activity. However, simultaneous administration is not feasible as 5FU and LV are chemically incompatible, so the maximum possible interaction for benefit is not achieved Deflexifol, an all in one formulation of 5FU/LV with cyclodextrin (HP-β-CD 100mg/ml, 5-FU 15mg/ml & LV 1mg/ml) at physiological pH, was developed to improve efficacy and tolerance. Methods: A phase I dose-escalation trial to assess the safety, tolerability, MTD and DLT of Deflexifol given in two schedules has been completed. Secondary objectives included the pharmacokinetic (PK) profile and efficacy outcomes. Cohorts of patients with advanced malignancy after failure of standard treatment received Deflexifol as 46-h infusion Q2W or bolus weekly x6 in a standard 3+3 phase I design with no intra-patient dose escalation from dose level 1: 375mg/m² bolus or 1200mg/m² infusional up to dose level 5: 575mg/m² bolus or 3600mg/m² infusional. PK sampling of 5FU and dihydroFU was conducted on all patients to assess PK variability and adequacy of dosing. Results: 40 patients (21 infusional, 19 bolus) with breast (7), colorectal (24), other GI (6) & NSCLC (3) received a total 293 courses of treatment. No > grade 1 toxicity was noted at 375-475 mg/m2 bolus, or at 1200-2400 mg/m2 infusion. The DLT in bolus schedule was grade 3 diarrhea and myelosuppression at 575 mg/m2, with no DLT in the infusion schedule at the maximum dose 3600 mg/m2. The MTD have been established for both treatment arms: bolus 525mg/m²; 46-h infusion 3,600mg/m², with no grade IV toxicity observed. Other grade 3 toxicities were nausea, vomiting, and raised liver function tests. 5FU PK in this mixture is similar to 5FU alone. Encouraging efficacy results were seen with partial response in 1 patient and stable disease in 23 patients. Median PFS was (12.3 wks) and OS was (24.8 wks). Conclusions: Deflexifol has little toxicity and is effective in bolus and infusion schedules at doses equal to or greater than those feasible with 5FU and LV infused separately. A first-line phase II study in combination with oxaliplatin is planned. Clinical trial information: 044867.