Phase I Study of the Tolerability and Pharmacokinetics of Palifermin in Children Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

The maximum tolerated dose of palifermin, a keratinocyte growth factor, in children is not known, and its pharmacokinetics in this population has not been well studied. This is a phase I study of palifermin was designed to evaluate its tolerability at doses of 40, 60, and 90 μg/kg/day in children age 2-18 years of age, receiving a myeloablative preparative regimen for allogeneic hematopoietic stem cell transplantation (HSCT). In each cohort, palifermin was given for 3 consecutive days before the preparative regimen and for 3 days after the stem cell infusion. Twelve patients were enrolled. Palifermin 90 μg/kg/day was tolerated in 6 patients without dose-limiting toxicity. All patients had at least 1 adverse event, mostly National Cancer Institute grade 1 or 2 severity. Skin rash, grade 2 or lower, was the most common adverse event, seen in 67% of patients. Only 3 patients (25%) had mucositis. The area under the concentration–time curve increased proportionally to the dose, and approximately 97% of palifermin exposure occurred in the first 24 hours after administration. Palifermin clearance increased linearly with body weight, supporting dosing by body weight. The mean clearance was 1893 mL/hour/kg, and it did not change significantly between administration of the first and last doses (P = .80). The mean elimination half-life was 4.6 hours. Our data show that palifermin was tolerated at a dose of 90 μg/kg/day, and exhibits linear pharmacokinetics in children undergoing allogeneic HSCT.