Reid, Joel M.

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.

9017 Background: Bevacizumab is a humanized monoclonal antibody targeting the vascular endothelial growth factor (VEGF-A) that has demonstrated significant growth inhibition in several pre-clinical models of pediatric solid tumors. However, the agent has never been tested in pediatric patients. Methods: A phase I dose escalation study in children with refractory solid tumors was conducted to define the dose limiting toxicities (DLTs), and to determine the pharmacokinetics (PK) and recommended phase II dose of bevacizumab administered by IV infusion every 2 weeks in 28-day cycles. Cohorts were enrolled at dose levels of 5, 10, and 15 mg/kg; the final dose level was expanded to include at least 3 children <6 years of age. Serial blood samples were collected for PK, plasma VEGF concentration, and circulating mature and progenitor endothelial cells (CECs/CEPs). Results: 20 patients (10 male), median age 13 yrs (range 1–21), were enrolled at dose levels 5 (n=3), 10 (n=3), and 15 (n=14) mg/kg. 18 patients were fully evaluable for toxicity (one withdrew consent prior to treatment and the second was removed for rapid disease progression). A total of 67 cycles were administered with a median of 3 per patient (range 1–16). Treatment was well tolerated and no DLTs were observed. Only one grade 3 toxicity, lymphopenia, was attributed to drug. Non-dose limiting, grade 1–2 toxicities included infusional reaction (n=3), rash (n=3), mucositis (n=2), and proteinuria (n=3). There was no hypertension, hemorrhage or thrombosis reported. There were no partial or complete responses; 3 pts with Ewings and 2 pts with soft tissue sarcoma had disease stabilization for > 3 months. The serum exposure to bevacizumab as measured by AUC appeared to increase in proportion to dose. The median clearance of bevacizumab was 4.1 ml/day/kg (range 3.2–15.9), and the median T1/2 was 11.8 days (range 3.9–14.6). In some patients, a rapid rate of rise in plasma VEGF, increase in mature CECs or decrease in CEPs was observed. Conclusion: Bevacizumab at doses up to 15mg/kg every two weeks is well tolerated in children with solid tumors. No significant financial relationships to disclose.

3044 Background: XL647 is an orally bioavailable small molecule inhibitor of multiple receptor tyrosine kinases involved in tumor cell growth, angiogenesis, and metastasis, including EGFR (erbB1), erbB2, VEGFR2/KDR, and EphB4. Methods: Patients (pts) with ASM were enrolled in successive cohorts to receive XL647 orally as a single dose on day 1 with PK sampling, followed by 5 continuous daily doses starting on day 4 with additional PK sampling. Pts then continued to receive XL647 for 5 consecutive days, followed by a break, with cycles repeating every 14 days. Tumor imaging was conducted at baseline, after the first 3 or 4 cycles, and then after every 4 cycles. Pts were allowed to stay on-study in the absence of unacceptable toxicity until evidence of disease progression. Results: A total of 37 pts have been treated across 9 dose levels to date: 0.06, 0.12, 0.19, 0.28, 0.39, 0.78, 1.56, 3.12, 4.68, and 7.0 mg/kg. One pt at 3.12 mg/kg had a dose limiting toxicity (DLT) of asymptomatic QTc prolongation on electrocardiogram, resulting in expansion of that cohort. The first two pts who received 7.0 mg/kg experienced DLTs of grade 3 diarrhea, requiring dose reduction. Both pts from the 7.0 mg/kg cohort tolerated 4.68 mg/kg well. Expansion of the 4.68 mg/kg cohort to 6 pts occurred without further DLTs and this is considered the maximum tolerated dose (MTD). One serious adverse event, grade 4 pulmonary embolism, was considered possibly related to study treatment in a pt dosed at 0.28 mg/kg. PK analysis indicates that XL647 shows approximately dose-proportional exposure, a mean time to maximal concentration (tmax) of 6–9 hours and an elimination half-life of 50–70 hours. To date, 1 pt (non-small cell lung cancer [NSCLC]) from cohort 1 had a partial response and 7 others (NSCLC [2], chordoma [2], adenoid cystic carcinoma, adrenocortical carcinoma, colorectal) have had prolonged stable disease (>3 months). Conclusions: XL647 has been well tolerated. An MTD of 4.68 mg/kg oral dosing for 5 consecutive days every 14 days has been established. Exploration of additional dosing schedules is ongoing, including continuous daily dosing. [Table: see text]

1562 Background: Prior studies have shown additive effects of CPT-11 in combination with BCNU, and radiosensitizing effects of CPT-11 in gliomas. Methods: All pts had GBM by central review prior to registration. With MTD based on a pilot study (Arm A), those not receiving anticonvulsants (non-EIAC, Arm C) received RT with concomitant CPT-11 (125 mg/M2/wk × 4, cycle 1), followed by BCNU (100 mg/M2 q 6 wk) + CPT-11 (75 mg/M2/wk × 4, q 6 wks, cycles 2–5) beginning within 4 wks of RT. Pts on EIAC (Arm B) received CPT-11 (400 mg/M2/wk × 4, cycle 1) during RT, then post-RT BCNU (100 mg/M2 q 6 wk) + CPT-11 (400 mg/M2/wk q 6 wks, cycles 2–5). Dose de-escalations (but no escalations) were allowed. Toxicity was graded by CTC v. 3.0. Primary endpoint was overall survival at 12 mo (OS12), with a interim futility analysis after 12 mos. follow up in the first 35 patients. 18 “successes” (survival > 12 mo) were required to proceed. Results: There were 56 pts treated (20 Arm A, 12 Arm B, 24 Arm C). Six pts on Arm A developed toxicity at the pilot CPT-11 cycle 2–5 dose of 125mg/M2, requiring reduction (75 mg/M2) for the remainder of Arm A and all Arm C pts. The decision rule for the first 35 patients was not met, with inclusion of the 6 Arm A pts (14 successes, 19 failures, 2 incomplete data) or without these pts ( 13 successes, 20 failures, 2 incomplete). In the 35 pts with mature data, the best confirmed response was PR in 2 (6%), REGR in 4 (11%) and stable (>4 wks, STAB) disease in 7 (20%). For the 56 pts (51 with mature data), PR, REGR and STAB were noted in 4%, 16%, and 39% respectively. Reason for end of treatment (N=56) was: completion of study treatment (13%); pt refusal (11%); adverse event (9%); progression (39%); all cause death (9%); too early (13%) or other (7%). In the 51 pts whose data is mature, progression free survival at 6 mos (PFS6) was 29.8% (95% CI: 19.1, 46.3); PFS12 was 16.5% (95% CI: 8.3, 32.9) and OS at 12 mos was 45.4% (95% CI: 32.7, 63). Overall median survival was 10.7 mos (95% CI: 7.8, 14.5). Conclusions: Although limited activity (PR+REGR+STAB) of this combination was demonstrated, the decision rule (minimum OS12 “successes”) was not reached, and tolerability of this regimen was only moderate. We consider the regimen as not superior to results obtained with other regimens in prior NCCTG studies. No significant financial relationships to disclose.

9563 Background: Both temozolomide (TEM) and vincristine (VCR) can increase the preclinical activity of low-dose protracted irinotecan (IRN) against pediatric solid tumors. Because these drugs have different dose-limiting toxicities (DLTs) and mechanisms of action, we combined these three agents and sought to determine the maximum tolerated dose (MTD) of orally administered IRN when given with fixed- dose TEM and VCR in children with relapsed or refractory solid tumors, using the antibiotic cefixime to reduce IRN-associated diarrhea. Methods: We studied two dose levels of oral IRN (35 or 50 mg/m2) administered on days 1–5 and 8–12, combined with oral TEM 100 mg/m2 on days 1–5 and intravenous VCR 1.5 mg/m2 on days 1 and 8. Courses were repeated every 21 days. Oral cefixime was started 5 days before chemotherapy and continued daily. Results: Of 21 patients enrolled, 17 (ages 3–21, median 14 yrs) were evaluable for toxicity and have to date received 46 courses (range 1–8, median 2). At the IRN dose of 50 mg/m2/d, 4 of 12 patients had DLT, including elevated ALT/AST (1), abdominal pain (1), hypokalemia (1), anorexia (1), thrombocytopenia (1), and fatal liver failure in a patient with metastatic disease in the liver and porta hepatis (1). In contrast, none of 5 patients treated at the dose of 35 mg/m2/d experienced first-course DLT, defining this dose as the MTD. UGT1A1 genotype did not correlate with DLT in this small trial. The median SN-38 lactone area under the curve (0–6h) at the IRN dose of 50 mg/m2/day was 13.5 ng/ml*h (range 3.8 to 30.9); pharmacokinetic analysis of patients treated at 35 mg/m2/day is ongoing. Six patients with the following tumors received more than 2 courses: neuroblastoma, ependymoma, hepatoblastoma, fibrillary astrocytoma, osteosarcoma, and Ewing sarcoma. Central review of response data is underway. Three patients continue on therapy at the MTD. Conclusions: Oral administration of IRN together with TEM and VCR was feasible and well tolerated at the MTD of 35 mg/m2 given dx5x2. Further study using a shorter 5-day course of oral IRN is planned. No significant financial relationships to disclose.

3598 Background: Drug resistance to topotecan can be the result of BCRP/ABCG2 expression. BCRP is a member of the ABC transporter family that pumps anticancer drugs out of the cell. Lapatinib is a potent and selective dual inhibitor of epidermal growth factor receptor (EGFR or ErbB1) and ErbB2 (Her2/Neu). 4-aminoquinazoline tyrosine kinase inhibitors have been shown to enhance the cytotoxicity of topotecan through inhibition of BCRP-mediated drug efflux in cancer cells. Methods: Thirty-seven patients with advanced stage cancers were enrolled at escalating dose levels of lapatinib and topotecan in cohorts IA, IB and IIB (MTD). Treatment schedule included lapatinib (750 - 1500 mg/d) daily for 21 (cohort IA) or 28 days (cohort IB) and topotecan (2.4 - 4.0 mg/ m2), days 1, 8 and 15; cycles were repeated every 28 days. Three patients were treated at each dose level, 18 on cohort IA, 9 on cohort IB and 10 at MTD (cohort IIB). Assessments of toxicity were performed with each cycle and clinical response was determined per RECIST criteria every other cycle. Results: The MTD for cohorts IA and IB was reached at a dose of 1250 mg of lapatinib and 3.2 mg/m2 of IV topotecan on days 1, 8 and 15. No DLT were seen during the dose escalation stage of cohorts IA and IB. Ten patients were enrolled at the MTD. There were no grade 4+ events. Thirteen grade 3+ events, considered to be related to treatment, were seen in 6 patients. The most common grade 3+ toxicities included dehydration (2) diarrhea (2), nausea (3), vomiting (2), neutropenia (1), thrombocytopenia (1), and fatigue (1). No abnormalities in left ventricular ejection fraction were noted. Stable disease was seen in 46% of the 37 patients. Conclusions: The combination of lapatinib and topotecan is a well-tolerated regimen. The MTD for the combination is lapatinib 1,250 mg orally once daily for 21 or 28 days and topotecan 3.2 mg/m2 on days 1, 8 and 15. Pharmacokinetic analysis for drug interaction will be available for presentation at the meeting. Supported in part by GSK and Mayo Clinic No significant financial relationships to disclose.

2039 Background: Vorinostat (V) is an oral inhibitor of histone deacetylase. In preclinical studies it inhibits growth of glioblastoma (GBM) cell lines and has supra-additive activity when combined with TMZ. Methods: The North American Brain Tumor Consortium (NABTC) is conducting a phase I study of V in combination with TMZ in patients with malignant gliomas (MG). Eligibility criteria are histologically proven GBM and anaplastic gliomas (AG) who have received radiotherapy and have not progressed on temozolomide, > 18 yrs old, life expectancy > 8 weeks, KPS > 60, adequate bone marrow reserve and organ function. There was no limitation to the type of antiepileptic drugs that could be used. All patients received TMZ at a dose of 150 mg/m2/day on days 1–5 days every 28 days. Variable doses of V were administered with food on days 1–14 every 28 days. Dose-limiting toxicities (DLT), determined during the first 4 weeks of therapy, were defined as any grade 4 hematologic toxicity except for grade 3 thrombocytopenia, and any grade 3 non-hematologic toxicities. Escalation was performed in standard groups of 3. The maximum tolerated dose (MTD) was defined as the dose at which DLTs occurred in no more than 1/6 patients. PKs were determined on cycle 1 for TMZ, V and its metabolites. Results: To date, 19 eligible patients have been enrolled (15 GBM; 4 AG). Patients’ characteristics are 11 male, 8 female; median age 54 yrs (36–78); median KPS 90 (70–100). DLTs were encountered at 300 mg bid of vorinostat (1 grade 3 thrombocytopenia; 1 grade 3 fatigue in 3 patients), 200 mg tid (1 grade 3 nausea, 1 grade 4 thrombocytopenia in 3 patients) and 200 mg twice daily (grade 3 fatigue in 2/6 patients). No DLTs were encountered in 6 patients receiving 300 mg daily. TMZ PKs included [n=16: Cmax 5.2 (± 1.55) μg/ml; AUC 20.1 (±4.66) μg x hr/ml; t1/2 1.9 (±0.32)/hr]. Vorinostat PKs (300mg dose level) were [n=4; Cmax 267 (±174) ng/ml; AUC0–8 603 (±197) ng x hr/ml]. The t1/2 for V and its glucuronide metabolite were identical (1.6 hrs) vs. 5.6 hrs for the acid metabolite. Conclusions: The MTD of vorinostat in combination with TMZ is 300 mg daily on days 1–14 every 28 days. Final PK results, and toxicities from an additional 10 patients enrolled at the MTD will be presented. [Table: see text]

2004 Background: Vorinostat is a histone deacetylase inhibitor that represents a rational therapeutic target in GBM. Methods: Recurrent GBM patients (pts) having received = 1 prior chemo regimen for progressive disease were eligible. Vorinostat dose was 200 mg bid x 14 days q 3 weeks. We applied a phase II design which had 90% power to declare the regimen active if the study PFS6 rate was 25%, a 15% rate increase over PFS6 in historical controls (10%). Results: 68 patients were treated. Grade 3+ non-hematologic toxicity consisting mainly of fatigue, diarrhea and dehydration occurred in 23% of pts; Grade 3+ hematologic toxicity consisting mainly of thrombocytopenia occurred in 25% of pts. Intra-patient dose escalation to 300 mg bid resulted in higher incidence of grade 3+ thrombocytopenia (45%) and was aborted. Pts receiving enzyme-inducing anticonvulsants (EIAC) had significantly less grade 3 + non-hematologic toxicity (p=0.01) and grade 3/4 thrombocytopenia (p=0.04). Pharmacokinetic analysis showed lower vorninostat C-max and AUC (0–24h) values and higher vorinostat-glucuronide C-max and AUC (0–24h) values in EIAC pts, although this did not reach statistical significance. The trial met the prospectively defined primary efficacy endpoint at the planned interim analysis with 5 of the first 22 patients (23%) being progression-free at 6 mo. RNA array analysis, performed in paired baseline and post-vorinostat treatment samples in a separate subgroup of 5 surgical recurrent GBM pts, who received vorinostat for 6 doses prior to surgery, showed upregulation of E-cadherin (p=0.02), thus indicating a biologic effect of the HDAC inhibitor on the glioblastoma tumors. Histone acetylation, Akt, phospho-Akt, P21Waf1/Cip1 and P27Kip1 expression analysis in all patients and correlation with outcome is ongoing. Conclusions: Vorinostat is well tolerated in recurrent GBM patients. EIAC patients have less toxicity, likely due to increased vorinostat metabolism via glucuronidation. Interim efficacy analysis is indicative of antitumor activity. Final efficacy analysis, RNA array data and correlative tissue analysis will be reported. No significant financial relationships to disclose.

Single nucleotide variants in the open reading frames (ORFs) of pharmacogenes are important causes of interindividual variability in drug response. The functional characterization of variants of unknown significance within ORFs remains a major challenge for pharmacogenomics. Deep mutational scanning (DMS) is a high‐throughput technique that makes it possible to analyze the functional effect of hundreds of variants in a parallel and scalable fashion. We adapted a “landing pad” DMS system to study the function of missense variants in the ORFs of cytochrome P450 family 2 subfamily C member 9 ( CYP2C9 ) and cytochrome P450 family 2 subfamily C member 19 ( CYP2C19 ). We studied 230 observed missense variants in the CYP2C9 and CYP2C19 ORFs and found that 19 of 109 CYP2C9 and 36 of 121 CYP2C19 variants displayed less than ~ 25% of the wild‐type protein expression, a level that may have clinical relevance. Our results support DMS as an efficient method for the identification of damaging ORF variants that might have potential clinical pharmacogenomic application.