Ahern, Charlotte H.

2538 Background: Trebananib is a first-in-class peptibody (peptide-Fc fusion protein) that selectively inhibits Angiopoietin 1 and Angiopoietin 2 to inhibit interaction with the Tie2 receptor tyrosine kinase and prevent angiogenesis by a VEGF independent mechanism. A pediatric phase 1 trial was performed to define the dose limiting toxicities (DLT), maximum tolerated dose (MTD) and pharmacokinetics (PK) of trebananib. Methods: Trebananib was administered as a weekly 30 - 60 minute IV infusion. Three dose levels (10, 15 or 30 mg/kg/dose) were evaluated using a rolling-six design. PK sampling and analysis of peripheral blood biomarkers was performed during the first 4 weeks of therapy. Results: Fifteen eligible patients (14 evaluable for toxicity) with a median age of 14 yrs (range, 3 to 20) and diagnoses of neuroblastoma (n=4), rhabdomyosarcoma (n=3), Ewing sarcoma (n=3), osteosarcoma (n=2), other soft tissue sarcoma (n=2), or nasopharyngeal carcinoma (n=1) have been enrolled. There were no DLTs observed at either the 10 mg/kg (n=6 pts) or 15 mg/kg (n=3 pts) dose. 1/6 pts receiving 30 mg/kg/dose developed DLT (venous thrombosis at a central line site). Non-dose limiting grade 3 or 4 toxicities included lymphopenia (n=2) hypertension (n=1), and neutropenia (n=1). Response in evaluable patients after eight weeks of therapy included stable disease (n=6 pts) and progressive disease (n=7 pts). PK were linear over the 3 dose levels, with t1/2 and Clpvalues of 69±18 h and 1.6±0.5 ml/h/kg, respectively. Conclusions: Trebananib is well tolerated in pediatric patients with recurrent or refractory solid tumors with recommended Phase 2 dose of 30 mg/kg. Correlative biology studies will be presented. Further study is planned to evaluate tolerability and changes in vascular permeability in patients with primary CNS tumors. Clinical trial information: NCT01538095.

9581 Background: AKT, a serine threonine protein kinase, is activated downstream of phosphatidylinositol 3-kinase (PI3K) which transmits signals from cytokines, growth factors and oncoproteins to multiple targets. Activated AKT regulates survival, proliferation, and growth. The PI3K/AKT pathway is downstream of most of the common growth factor tyrosine kinase receptors in cancer, e.g., EGFR, HER2, IGFR, etc., and is a driver of tumor progression in many cancers. AKT protein kinase is activated in many pediatric solid tumors, including glioblastoma, malignant rhabdoid tumors, neuroblastoma, synovial sarcoma, rhabdomyosarcoma and medulloblastoma. MK2206, an oral allosteric AKT1, 2,3 inhibitor, has demonstrated antitumor activity in in vitro and in vivo cancer models.A phase I trial evaluating MK2206 was conducted in children with refractory solid tumors. Methods: Using a rolling-6 design, MK2206 was administered either once every 7 days (schedule 1), or once every other day (schedule 2) in a 28-day cycle. Serial PK studies were obtained on day 1, cycle 1 and trough samples were obtained on days 7, 14, 21 and 28. Biological studies included analysis of PI3K/PTEN/AKT-cell signaling pathway in pre and post-therapy in PBMC and in tumors at diagnosis or recurrence. Results: Forty-five patients [23 males, median age 13.6 years (range 3.1-21.9)] with malignant glioma (14), ependymoma (4), hepatocellular carcinoma (3), gliomatosis cereberi (2) or other tumors (22) were enrolled; 34 were fully evaluable for toxicity (schedule 1 n=17; schedule 2 n=17). Schedule 1 DLTs included: grade 3 dehydration in 1/6 patients at 28 mg/m2; grade 4 hyperglycemia and neutropenia in 1/6 patients at 45 mg/m2. There were no DLTs at 35 mg/m2 and dose level 4 (58 mg/m2) is currently open for patient accrual with one enrollment. Schedule 2 DLTs included: grade 3 alkaline phosphatase in 1/6 patients at 90 mg/m2; grade 3 rash in 1/6 patients at 120 mg/m2), and grade 3 rash in 2/6 patients at 155 mg/m2. Conclusions: The recommended pediatric phase II dose of weekly MK2206 is 120 mg/m2 and the last cohort of patients to the every other day dosing schedule of MMK206 is enrolling. PK and PD data are currently being analyzed and will be presented.

Abstract Purpose: To determine the MTD, dose-limiting toxicities (DLT), pharmacokinetics, and biologic effects of cixutumumab administered in combination with temsirolimus to children with refractory solid tumors. Experimental Design: Cixutumumab and temsirolimus were administered intravenously once every 7 days in 28-day cycles. Pharmacokinetic and biology studies, including assessment of mTOR downstream targets in peripheral blood mononuclear cells, were performed during the first cycle. Results: Thirty-nine patients, median age 11.8 years (range, 1–21.5), with recurrent solid or central nervous system tumors were enrolled, of whom 33 were fully assessable for toxicity. There were four dose levels, which included two dose reductions and a subsequent intermediated dose escalation: (i) IMC-A12 6 mg/kg, temsirolimus 15 mg/m2; (ii) IMC-A12 6 mg/kg, temsirolimus 10 mg/m2; (iii) IMC-A12 4 mg/kg, temsirolimus 8 mg/m2; and (iv) IMC-A12 6 mg/kg, temsirolimus 8 mg/m2. Mucositis was the predominant DLT. Other DLTs included hypercholesterolemia, fatigue, thrombocytopenia, and increased alanine aminotransferase. Target inhibition (decreased S6K1 and PAkt) in peripheral blood mononuclear cells was noted at all dose levels. Marked interpatient variability in temsirolimus pharmacokinetic parameters was noted. At 8 mg/m2, the median temsirolimus AUC was 2,946 ng • h/mL (range, 937–5,536) with a median sirolimus AUC of 767 ng • h/mL (range, 245–3,675). Conclusions: The recommended pediatric phase II doses for the combination of cixutumumab and temsirolimus are 6 mg/kg and 8 mg/m2, respectively. Clin Cancer Res; 21(7); 1558–65. ©2014 AACR.

BackgroundWe report results of a phase I trial designed to estimate the maximum tolerated dose (MTD), describe dose‐limiting toxicities (DLT), and characterize the pharmacokinetic profile of MK‐2206, an AKT inhibitor, in children with refractory or recurrent malignancies.ProcedureMK‐2206 was administered either every other day (Schedule 1), or once a week (Schedule 2) in a 28‐day cycle. Dose escalations in increments of ∼30% were independently made in each part using the rolling‐six design. Serial pharmacokinetic (PK) studies were obtained. Biological studies include analysis of PI3K/PTEN/AKT‐cell signaling pathway in pre and post‐therapy in PBMC and in tumors at diagnosis or recurrence.ResultsFifty patients (26 males, median age 12.6 years [range, 3.1–21.9]) with malignant glioma (16), ependymoma (4), hepatocellular carcinoma (3), gliomatosis cereberi (2), or other tumors (22) were enrolled; 40 were fully evaluable for toxicity (Schedule 1, n = 23; Schedule 2, n = 17). Schedule 1 DLTs included: grade 3 dehydration in 1/6 patients at 28 mg/m2; grade 4 hyperglycemia and neutropenia in 1/6 patients at 45 mg/m2; and grade 3 rash in 3/6 patients at dose level 4 (58 mg/m2). Schedule 2 DLTs included: grade 3 alkaline phosphatase in 1/6 patients at 90 mg/m2; grade 3 rash in 1/6 patients at 120 mg/m2; and grade 3 rash in 2/6 patients at 155 mg/m2.ConclusionsThe recommended pediatric phase 2 dose of MK‐2206 is 45 mg/m2/dose every other day or 120 mg/m2/dose weekly. PK appeared linear over the dose range studied. Pediatr Blood Cancer 2014;61:1246–1251. © 2014 Wiley Periodicals, Inc.

Abstract Purpose: Imetelstat is a covalently-lipidated 13-mer thiophosphoramidate oligonucleotide that acts as a potent specific inhibitor of telomerase. It binds with high affinity to the template region of the RNA component of human telomerase (hTERC) and is a competitive inhibitor of telomerase enzymatic activity. The purpose of this study was to determine the recommended phase II dose of imetelstat in children with recurrent or refractory solid tumors. Experimental Design: Imetelstat was administered intravenously more than two hours on days 1 and 8, every 21 days. Dose levels of 225, 285, and 360 mg/m2 were evaluated, using the rolling-six design. Imetelstat pharmacokinetic and correlative biology studies were also performed during the first cycle. Results: Twenty subjects were enrolled (median age, 14 years; range, 3–21). Seventeen were evaluable for toxicity. The most common toxicities were neutropenia, thrombocytopenia, and lymphopenia, with dose-limiting myelosuppression in 2 of 6 patients at 360 mg/m2. Pharmacokinetics is dose dependent with a lower clearance at the highest dose level. Telomerase inhibition was observed in peripheral blood mononuclear cells at 285 and 360 mg/m2. Two confirmed partial responses, osteosarcoma (n = 1) and Ewing sarcoma (n = 1), were observed. Conclusions: The recommended phase II dose of imetelstat given on days 1 and 8 of a 21-day cycle is 285 mg/m2. Clin Cancer Res; 19(23); 6578–84. ©2013 AACR.

Purpose Pazopanib, an oral multikinase angiogenesis inhibitor, prolongs progression-free survival in adults with soft tissue sarcoma (STS). A phase I pharmacokinetic and pharmacodynamic study of two formulations of pazopanib was performed in children with STS or other refractory solid tumors. Patients and Methods Pazopanib (tablet formulation) was administered once daily in 28-day cycles at four dose levels (275 to 600 mg/m 2 ) using the rolling-six design. Dose determination for a powder suspension was initiated at 50% of the maximum-tolerated dose (MTD) for the intact tablet. Ten patients with STS underwent dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) scanning at baseline and 15 ± 2 days after initiation of pazopanib at the tablet MTD. Results Fifty-three patients were enrolled; 51 were eligible (26 males; median age, 12.9 years; range, 3.8 to 23.9 years). Hematologic and nonhematologic toxicities were generally mild, with dose-limiting lipase, amylase, and ALT elevation, proteinuria, and hypertension. One patient with occult brain metastasis had grade 4 intracranial hemorrhage. The MTD was 450 mg/m 2 for tablet and 160 mg/m 2 for suspension. Steady-state trough concentrations were reached by day 15 and did not seem to be dose dependent. One patient each with hepatoblastoma or desmoplastic small round cell tumor achieved a partial response; eight patients had stable disease for ≥ six cycles, seven of whom had sarcoma. All patients with evaluable DCE-MRI (n = 8) experienced decreases in tumor blood volume and permeability (P < .01). Placental growth factor increased, whereas endoglin and soluble vascular endothelial growth factor receptor-2 decreased (P < .01; n = 41). Conclusion Pazopanib is well tolerated in children, with evidence of antiangiogenic effect and potential clinical benefit in pediatric sarcoma.