Stork, Linda C.

9019 Background: Pemetrexed is a new multi-targeted antifol that inhibits enzymes involved in the de novo biosynthesis of thymidine and purine nucleotides. Methods: A phase 1 dose escalation and pharmacokinetic study (PK) was performed in children with refractory solid tumors to define the dose limiting toxicities (DLTs) and a recommended phase 2 dose. Pemetrexed was administered as a 10 min iv infusion every 21 days. All patients received folic acid (400 mcg/day po), vitamin B12 (500–1000 mcg every 3rd course IM) and dexamethasone (0.1 mg/kg/dose bid × 3 days each course) . Cohorts of 3 to 6 children were enrolled at dose levels of 400, 520, 670, 870, 1,130, 1,470, 1,910 and 2,480 mg/m2. DLT was defined as any Gr. 3 or 4 non-hematological toxicity (except nausea/vomiting, alopecia, or AST/ALT elevation that returns to Gr. 1), Gr. 4 neutropenia or Gr. 4 thrombocytopenia ≥ 7 days. Results: 33 subjects (31 fully evaluable for toxicity), median age of 12 yrs (range, 1–21), with diagnoses including osteosarcoma (12), Ewing’s sarcoma (3), hepatoblastoma (2), renal cell carcinoma (2), brainstem glioma (3), glioma (3), and other (n=8) were enrolled. DLT occurred in 1/6 patients at 1,470 mg/m2 (Gr. 3 AST and ALT), and in 2/4 at 2,480 mg/m2 (Gr. 3 ANC and Gr. 3 rash in both). Other DLTs at 2,480 mg/m2 that occurred in 1 patient included Gr. 3 diarrhea and rectal hemorrhage, and Gr. 4 thrombocytopenia, lipase, GGT, hypophosphatemia, hypokalemia and hyponatremia. At 1,910 mg/m2, 0/6 patients had DLT. The median number of courses administered was 1 (range 1 to 17). No CRs or PRs have been observed. Results of PK and other correlative studies will be presented. Conclusions: The recommended phase 2 dose of pemetrexed for children and adolescents with recurrent solid tumors is 1,910 mg/m2 administered q21 days with dexamethasone, folic acid and B12 supplementation. A phase II COG study is planned. No significant financial relationships to disclose.

PurposeWe report results of a phase I trial and pharmacokinetic study of pemetrexed (LY231514) in children and adolescents with refractory solid tumors. Pemetrexed is a novel antifolate that inhibits multiple enzymes necessary for the biosynthesis of thymidine and purine nucleotides. The purpose of this study was to determine the maximum-tolerated dose (MTD), dose-limiting toxicities (DLTs), and pharmacokinetic properties of pemetrexed in children.Patients and MethodsPemetrexed was administered as a 10-minute intravenous infusion every 21 days. Patients received vitamin B12and folic acid supplementation as well as dexamethasone prophylaxis. Cohorts of three to six children were enrolled at dose levels of 400, 520, 670, 870, 1,130, 1,470, 1,910, and 2,480 mg/m2. Pharmacokinetic studies were performed during the first course of treatment.ResultsThirty-three patients (31 assessable) with a median age of 12 years were enrolled. DLT occurred in one of six patients at 1,470 mg/m2and two of four patients at 2,480 mg/m2. The MTD was 1,910 mg/m2. The primary DLTs were neutropenia and rash. No objective antitumor responses were seen. Mean plasma clearance, half-life, and steady-state volume of distribution values were 2.3 L/h/m2, 2.5 hours, and 5.4 L/m2, respectively.ConclusionPemetrexed is well-tolerated in children with refractory solid tumors at doses similar to the MTD in adults. The recommended dose for phase II studies is 1,910 mg/m2administered every 21 days with dexamethasone, folic acid, and vitamin B12supplementation.