An open-label clinical trial evaluating safety and pharmacokinetics of two dosing schedules of panitumumab in patients with solid tumors

Purpose: This study evaluated safety, pharmacokinetics, and efficacy of 2 dose schedules and 2 infusion times of panitumumab in patients with advanced solid malignancies. Patients and Methods: This phase I multicenter, open-label study sequentially enrolled patients with advanced solid tumors refractory to standard therapy, or for which no standard therapy exists, to receive panitumumab 6 mg/kg every 2 weeks or 9 mg/kg every 3 weeks. Patients receiving panitumumab every 2 weeks received either all infusions over 60 minutes or a 60-minute infusion for the first dose followed by 30-minute infusions if the first infusion was well tolerated. Patients in the every-3-week cohort received 60-minute infusions. Safety outcomes included the incidence of adverse events and antipanitumumab antibody formation. Pharmacokinetic properties were determined. Efficacy endpoints included response rate and duration of response. Results: Eighty-six patients were enrolled; 84 (98%) received panitumumab. Treatment-related adverse events occurred in 90% of patients. Safety profiles were similar between patients receiving 30-minute (n = 20) and 60-minute (n = 43) infusions every 2 weeks and patients receiving panitumumab every 3 weeks (n = 21). Panitumumab exposure at steady state increased dose proportionally, and peak serum concentrations were similar in patients receiving either 30- or 60-minute infusions every 2 weeks. Objective responses were seen in 4 patients (5%) with colon, rectal, esophageal, and bladder cancers. Conclusion: Similar drug exposures and safety profiles were observed in patients receiving panitumumab 6 mg/kg every 2 weeks with either 30- or 60-minute infusions and antitumor activity was seen in some patients. Exposure increased approximately dose proportionally at steady state.