Topotecan clearance based on a single sample and a population pharmacokinetic model: Application to a pediatric high-risk neuroblastoma clinical trial.

BACKGROUND: Topotecan, an antitumor drug with systemic exposure (SE)-dependent activity against many pediatric tumors has wide interpatient pharmacokinetic variability, making it challenging to attain the desired topotecan SE. The study objectives were to update our topotecan population pharmacokinetic model, to evaluate the feasibility of determining individual topotecan clearance using a single blood sample, and to apply this approach to topotecan data from a neuroblastoma trial to explore exposure-response relationships. PROCEDURE: Our previous population pharmacokinetic and covariate model was updated using data from 13 clinical pediatric studies. A simulation-based Bayesian analysis was performed to determine if a single blood sample could be sufficient to estimate individual topotecan clearance. Following the Bayesian approach, single pharmacokinetic samples collected from a Children's Oncology Group Phase III clinical trial (ANBL0532; NCT0056767) were analyzed to estimate individual topotecan SE. Associations between topotecan SE and toxicity or early response were then evaluated. RESULTS: The updated population model included the impact of patient body surface area (BSA), age, and renal function on topotecan clearance. The Bayesian analysis with the updated model and single plasma samples showed that individual topotecan clearance values were estimated with good precision (mean absolute prediction error ≤16.2%) and low bias (mean prediction error ≤7.2%). Using the same approach, topotecan SE was derived in patients from ANBL0532. The exposure-response analysis showed an increased early response after concomitant cyclophosphamide and topotecan up to a topotecan SE of 45 h ng/mL. CONCLUSIONS: A simple single-sample approach during topotecan therapy could guide dosing for patients, resulting in more patients reaching target attainment.

LRRK2 Inhibition by BIIB122 in Healthy Participants and Patients with Parkinson's Disease.

BACKGROUND: Leucine-rich repeat kinase 2 (LRRK2) inhibition is a promising therapeutic approach for the treatment of Parkinson's disease (PD). OBJECTIVE: The aim of this study was to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of the potent, selective, CNS-penetrant LRRK2 inhibitor BIIB122 (DNL151) in healthy participants and patients with PD. METHODS: Two randomized, double-blind, placebo-controlled studies were completed. The phase 1 study (DNLI-C-0001) evaluated single and multiple doses of BIIB122 for up to 28 days in healthy participants. The phase 1b study (DNLI-C-0003) evaluated BIIB122 for 28 days in patients with mild to moderate PD. The primary objectives were to investigate the safety, tolerability, and plasma pharmacokinetics of BIIB122. Pharmacodynamic outcomes included peripheral and central target inhibition and lysosomal pathway engagement biomarkers. RESULTS: A total of 186/184 healthy participants (146/145 BIIB122, 40/39 placebo) and 36/36 patients (26/26 BIIB122, 10/10 placebo) were randomized/treated in the phase 1 and phase 1b studies, respectively. In both studies, BIIB122 was generally well tolerated; no serious adverse events were reported, and the majority of treatment-emergent adverse events were mild. BIIB122 cerebrospinal fluid/unbound plasma concentration ratio was ~1 (range, 0.7-1.8). Dose-dependent median reductions from baseline were observed in whole-blood phosphorylated serine 935 LRRK2 (≤98%), peripheral blood mononuclear cell phosphorylated threonine 73 pRab10 (≤93%), cerebrospinal fluid total LRRK2 (≤50%), and urine bis (monoacylglycerol) phosphate (≤74%). CONCLUSIONS: At generally safe and well-tolerated doses, BIIB122 achieved substantial peripheral LRRK2 kinase inhibition and modulation of lysosomal pathways downstream of LRRK2, with evidence of CNS distribution and target inhibition. These studies support continued investigation of LRRK2 inhibition with BIIB122 for the treatment of PD. © 2023 Denali Therapeutics Inc and The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Brain delivery and activity of a lysosomal enzyme using a blood-brain barrier transport vehicle in mice.

Most lysosomal storage diseases (LSDs) involve progressive central nervous system (CNS) impairment, resulting from deficiency of a lysosomal enzyme. Treatment of neuronopathic LSDs remains a considerable challenge, as approved intravenously administered enzyme therapies are ineffective in modifying CNS disease because they do not effectively cross the blood-brain barrier (BBB). We describe a therapeutic platform for increasing the brain exposure of enzyme replacement therapies. The enzyme transport vehicle (ETV) is a lysosomal enzyme fused to an Fc domain that has been engineered to bind to the transferrin receptor, which facilitates receptor-mediated transcytosis across the BBB. We demonstrate that ETV fusions containing iduronate 2-sulfatase (ETV:IDS), the lysosomal enzyme deficient in mucopolysaccharidosis type II, exhibited high intrinsic activity and degraded accumulated substrates in both IDS-deficient cell and in vivo models. ETV substantially improved brain delivery of IDS in a preclinical model of disease, enabling enhanced cellular distribution to neurons, astrocytes, and microglia throughout the brain. Improved brain exposure for ETV:IDS translated to a reduction in accumulated substrates in these CNS cell types and peripheral tissues and resulted in a complete correction of downstream disease-relevant pathologies in the brain, including secondary accumulation of lysosomal lipids, perturbed gene expression, neuroinflammation, and neuroaxonal damage. These data highlight the therapeutic potential of the ETV platform for LSDs and provide preclinical proof of concept for TV-enabled therapeutics to treat CNS diseases more broadly.

Phase I expansion cohort to evaluate the combination of bevacizumab, sorafenib and low-dose cyclophosphamide in children and young adults with refractory or recurrent solid tumours.

BACKGROUND: Angiogenesis is critical for tumour growth and metastasis. Dual inhibition of vascular endothelial growth factors and platelet-derived growth factor receptors suppresses angiogenesis. This expansion cohort of a phase I study targeted angiogenesis with sorafenib, bevacizumab and low-dose cyclophosphamide in children and young adults with recurrent solid tumours. METHODS: An expansion cohort including patients with refractory or recurrent solid tumours was enrolled and received bevacizumab (15 mg/kg IV, day 1), sorafenib (90 mg/m2 po twice daily, days 1-21) and low-dose cyclophosphamide (50 mg/m2 po daily, days 1-21). Each course was 21 days. Toxicities were assessed using Common Terminology Criteria for Adverse Events, v3.0, and responses were evaluated by Response Evaluation Criteria in Solid Tumors criteria. Serial bevacizumab pharmacokinetic (PK) studies were performed during course 1. RESULTS: Twenty-four patients (15 males; median age 14.5 yrs; range 1-22 yr) received a median of 6 courses (range 1-18). Twelve patients had a bone or soft tissue sarcoma. The most common grade III/IV non-haematologic toxicities were hypertension (N = 4), hand/foot rash (N = 3) and elevated lipase (N = 3). The most common grade III/IV haematologic toxicities were neutropenia (N = 7) and lymphopenia (N = 17). Three patients (2 synovial sarcoma, 1 rhabdoid tumour) achieved a partial response and 18 had stable disease. The progression-free survival at 3 and 6 months were 78.1% (95% confidence interval [CI] 60.6-95.6%) and 54% (95% CI 30.2-78.2%), respectively. Bevacizumab PKs in 15 patients was similar to published adult PK results. CONCLUSIONS: Intravenous bevacizumab combined with oral sorafenib and low-dose cyclophosphamide was tolerated and demonstrated promising activity in a subset of childhood solid tumours.

Pharmacokinetic basis for dosing high-dose methotrexate in infants and young children with malignant brain tumours.

AIMS: No population pharmacokinetic studies of high-dose methotrexate (HDMTX) have been conducted in infants with brain tumours, which are a vulnerable population. The aim of this study was to evaluate HDMTX disposition in these children to provide a rational basis for MTX dosing. METHODS: Patients received 4 monthly courses of HDMTX (5 g/m2 or 2.5 g/m2 for infants aged ≤31 days) as a 24-h infusion. Serial samples were analysed for MTX by an enzyme immunoassay method. Pharmacokinetic parameters were estimated using nonlinear mixed effects population modelling. Demographics, concomitant medications and genetic polymorphisms were considered as pharmacokinetic covariates while MTX exposure and patient age were considered as covariates for Grade 3 and 4 toxicities. RESULTS: The population pharmacokinetics of HDMTX were estimated in 178 patients (age range 0.02-4.7 years) in 648 courses. The population clearance and volume were 90 mL/min/m2 and 14.4 L/m2 , respectively. Significant covariates on body surface area adjusted MTX clearance included estimated glomerular filtration rate and co-treatment with dexamethasone or vancomycin. No significant association was observed between MTX toxicity and MTX exposure, patient age, leucovorin dosage or duration. MTX clearance in infants ≤31 days at enrolment was 44% lower than in older infants, but their incidence of toxicity was not higher since they also received a lower MTX dosage. CONCLUSIONS: By aggressively following institutional clinical guidelines, HDMTX-related toxicities were low, and using covariates from the population pharmacokinetic model enabled the calculation of a rational dosage for this patient population for future clinical trials.

Combinatorial screening using orthotopic patient derived xenograft-expanded early phase cultures of osteosarcoma identify novel therapeutic drug combinations.

Lead discovery in osteosarcoma has been hampered by the lack of new agents, limited representative clinical samples and paucity of accurate preclinical models. We developed orthotopic patient-derived xenografts (PDXs) that recapitulated the molecular, cellular and histologic features of primary tumors, and screened PDX-expanded short-term cultures and commercial cell lines of osteosarcoma against focused drug libraries. Osteosarcoma cells were most sensitive to HDAC, proteasome, and combination PI3K/MEK and PI3K/mTOR inhibitors, and least sensitive to PARP, RAF, ERK and MEK inhibitors. Correspondingly, PI3K signaling pathway genes were up-regulated in metastatic tumors compared to primary tumors. In combinatorial screens, as a class, HDAC inhibitors showed additive effects when combined with standard-of-care agents gemcitabine and doxorubicin. This lead discovery strategy afforded a means to perform high-throughput drug screens of tumor cells that accurately recapitulated those from original human tumors, and identified classes of novel and repurposed drugs with activity against osteosarcoma.

Derivation of new equations to estimate glomerular filtration rate in pediatric oncology patients.

BACKGROUND AND OBJECTIVE: Monitoring renal function is critical in treating pediatric patients, especially when dosing nephrotoxic agents. We evaluated the validity of the bedside Schwartz and Brandt equations in pediatric oncology patients and developed new equations for estimated glomerular filtration rate (eGFR) in these patients. METHODS: A retrospective analysis was conducted comparing eGFR using the bedside Schwartz and Brandt equations to measured GFR (mGFR) from technetium-99m diethylenetriamine pentaacetic acid (99mTc-DTPA) between January 2007 and August 2013. An improved equation to estimate GFR was developed, simplified, and externally validated in a cohort of patients studied from September 2013 to June 2015. Carboplatin doses calculated from 99mTc-DTPA were compared with doses calculated by GFR-estimating equations. RESULTS: Overall, the bedside Schwartz and Brandt equations did not precisely or accurately predict measured GFR (mGFR). Using a data subset, we developed a five-covariate equation, which included height, serum creatinine, age, blood urea nitrogen (BUN), and gender, and a simplified version (two-covariates), which contained height and serum creatinine. These equations were used to estimate GFR in 2036 studies, resulting in precise and accurate predictors of mGFR values. Equations were validated in an external cohort of 570 studies; both new equations were more accurate in calculating carboplatin doses than either the bedside Schwartz or Brandt equation. CONCLUSIONS: Two new equations were developed to estimate GFR in pediatric oncology patients, both of which did a better job at estimating mGFR than published equations.

A phase II trial evaluating the feasibility of adding bevacizumab to standard osteosarcoma therapy.

Increased vascular endothelial growth factor (VEGF) expression in osteosarcoma correlates with a poor outcome. We conducted a phase II trial to evaluate the feasibility and efficacy of combining bevacizumab, a monoclonal antibody against VEGF, with methotrexate, doxorubicin and cisplatin (MAP) in patients with localized osteosarcoma. Eligible patients received two courses of MAP chemotherapy before definitive surgery at week 10. Bevacizumab (15 mg/kg) was administered 3 days before starting chemotherapy then on day 1 of weeks 3 and 5 of chemotherapy. After surgery, patients received MAP for a total of 29 weeks; bevacizumab was added every 2 or 3 weeks on day 1 of chemotherapy at least 5 weeks after surgery. Group sequential monitoring rules were used to monitor for unacceptable bevacizumab-related targeted toxicity (grade 4 hypertension, proteinuria or bleeding, grade 3 or 4 thrombosis/embolism, and grade 2-4 major wound complications). Thirty-one patients (median age 12.8 years) with localized osteosarcoma were enrolled. No unacceptable targeted toxicities were observed except for wound complications (9 minor and 6 major), which occurred in 15 patients; none required removal of prosthetic hardware or amputation. The estimated 4-year event-free survival (EFS) rate and overall survival rate were 57.5 ± 10.0% and 83.4 ± 7.8%, respectively. Eight (28%) of 29 evaluable patients had good histologic response (<5% viable tumor) to preoperative chemotherapy. The addition of bevacizumab to MAP for localized osteosarcoma is feasible but frequent wound complications are encountered. The observed histologic response and EFS do not support further evaluation of bevacizumab in osteosarcoma.

A molecular biology and phase II study of imetelstat (GRN163L) in children with recurrent or refractory central nervous system malignancies: a pediatric brain tumor consortium study.

Telomerase activation is critical in many cancers including central nervous system (CNS) tumors. Imetelstat is an oligonucleotide that binds to the template region of the RNA component of telomerase, inhibiting its enzymatic activity. We conducted an investigator-sponsored molecular biology (MB) and phase II study to estimate inhibition of tumor telomerase activity and sustained responses by imetelstat in children with recurrent CNS malignancies. In the MB study, patients with recurrent medulloblastoma, high-grade glioma (HGG) or ependymoma undergoing resection received one dose of imetelstat as a 2-h intravenous infusion at 285 mg/m(2), 12-24 h before surgery. Telomerase activity was evaluated in fresh tumor from surgery. Post-surgery and in the phase II study, patients received imetelstat IV (days 1 and 8 q21-days) at 285 mg/m(2). Imetelstat pharmacokinetic and pharmacodynamic studies were performed. Of two evaluable patients on the MB trial, intratumoral telomerase activity was inhibited by 95 % compared to baseline archival tissue in one patient and was inevaluable in one patient. Forty-two patients (40 evaluable for toxicity) were enrolled: 9 medulloblastomas, 18 HGG, 4 ependymomas, 9 diffuse intrinsic pontine gliomas. Most common grade 3/4 toxicities included thrombocytopenia (32.5 %), lymphopenia (17.5 %), neutropenia (12.5 %), ALT (7.5 %) and AST (5 %) elevation. Two patients died of intratumoral hemorrhage secondary to thrombocytopenia leading to premature study closure. No objective responses were observed. Telomerase inhibition was observed in peripheral blood mononuclear cells (PBMCs) for at least 8 days. Imetelstat demonstrated intratumoral and PBMC target inhibition; the regimen proved too toxic in children with recurrent CNS tumors.

Population Pharmacokinetics of Oral Topotecan in Infants and Very Young Children with Brain Tumors Demonstrates a Role of ABCG2 rs4148157 on the Absorption Rate Constant.

For infants and very young children with brain tumors, chemotherapy after surgical resection is the main treatment due to neurologic and neuroendocrine adverse effects from whole brain irradiation. Topotecan, an anticancer drug with antitumor activity against pediatric brain tumors, can be given intravenous or orally. However, high interpatient variability in oral drug bioavailability is common in children less than 3 years old. Therefore, this study aimed to determine the population pharmacokinetics of oral topotecan in infants and very young children, specifically evaluating the effects of age and ABCG2 and ABCB1 on the absorption rate constant (Ka), as well as other covariate effects on all pharmacokinetic parameters. A nonlinear mixed effects model was implemented in Monolix 4.3.2 (Lixoft, Orsay, France). A one-compartment model with first-order input and first-order elimination was found to adequately characterize topotecan lactone concentrations with population estimates as [mean (S.E.)]; Ka = 0.61 (0.11) h(-1), apparent volume of distribution (V/F) = 40.2 (7.0) l, and apparent clearance (CL/F) = 40.0 (2.9) l/h. After including the body surface area in the V/F and CL/F as a power model centered on the population median, the ABCG2 rs4148157 allele was found to play a significant role in the value of Ka Patients homozygous or heterozygous for G>A demonstrated a Ka value 2-fold higher than their GG counterparts, complemented with a 2-fold higher maximal concentration as well. These results demonstrate a possible role for the ABCG2 rs4148157 allele in the pharmacokinetics of oral topotecan in infants and very young children, and warrants further investigation.

Feasibility of Pegylated Interferon in Children and Young Adults With Resected High-Risk Melanoma.

BACKGROUND: Pegylated interferon α-2b (IFN α-2b) improves disease-free survival in adults with resected stage III melanoma. We conducted a study to determine the feasibility and safety of incorporating pegylated IFN α-2b as adjuvant therapy in the treatment of children and adolescents with high-risk melanoma. Pharmacokinetic studies of IFN α-2b and neuropsychological and quality of life (OL) assessments were performed. PATIENT AND METHODS: Eligible patients with resected American Joint Committee on Cancer Stage IIC, IIIA, and IIIB cutaneous melanoma received nonpegylated IFN α-2b 20 million units/m(2) /day intravenously 5 days per week for 4 weeks (induction) followed by pegylated IFN α-2b 1 µg/kg/dose weekly subcutaneously (SQ) for 48 weeks (maintenance). RESULTS: Twenty-three patients (15 females, median age 10 years) were enrolled. All patients completed induction therapy; five patients did not complete maintenance therapy either because of recurrent disease (n = 2) or toxicity (n = 3). The most common grade 3 and 4 toxicities of pegylated IFN α-2b were neutropenia (35%) and elevated liver transaminases (17%). The median nonpegylated IFN α-2b AUC0-∞ (5,026 pcg⋅hr/ml) was similar to adults. The median pegylated IFN α-2b exposure (48,480 pcg⋅hr/ml) was greater than the cumulative weekly exposure for nonpegylated IFN α-2b administered SQ three times per week (TIW). Validated measures demonstrated an improvement in QOL scores and no decline in psychological functioning over the course of therapy. CONCLUSIONS: Pegylated IFN α-2b 1 µg/kg/dose SQ weekly as maintenance therapy in children and adolescents with high-risk melanoma is feasible with tolerable toxicity and appears to yield higher exposures than nonpegylated IFN α-2b administered SQ TIW.

Phase II evaluation of sunitinib in the treatment of recurrent or refractory high-grade glioma or ependymoma in children: a children's Oncology Group Study ACNS1021.

Sunitinib malate is a small multi-targeted tyrosine kinase inhibitor that inhibits vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and stem cell factor receptor (KIT), which are highly expressed by some high-grade brain tumors. We conducted a phase II study to estimate the efficacy and further characterize the pharmacokinetics of sunitinib in pediatric patients with recurrent or refractory high-grade glioma (Stratum A) or ependymoma (Stratum B). This was a prospective, multicenter Phase II trial conducted through the Children's Oncology Group (ClinicalTrials.gov Identifier NCT01462695). Sunitinib, 15 mg/m2, was orally administered once daily for 4 weeks every 6 weeks. The safety and tolerability of sunitinib, an estimate of progression-free survival (PFS), analyses of sunitinib pharmacokinetics (PK) and pharmacodynamics modulation of plasma VEGF and VEGFR2 were also assessed. Thirty eligible patients (17 patients on Stratum A, 13 patients on Stratum B) were enrolled and 29 patients were evaluable for response. Sunitinib was reasonably well tolerated in children with recurrent ependymoma or high-grade glioma. Most adverse events were of mild-to-moderate severity and manageable with supportive treatment. While there was a statistically significant modulation of plasma VEGFR2 with sunitinib exposure, there were no sustained tumor responses. Both strata were closed at time of planned interim analysis as there was not sufficient efficacy associated with sunitinib in children with recurrent brain tumors. Sunitinib was well tolerated in children and young adults with recurrent high-grade glioma or ependymoma but had no single agent objective antitumor activity in these patients.

Neurocognitive and Patient-Reported Outcomes in Adult Survivors of Childhood Osteosarcoma.

IMPORTANCE: This study provides the first objective data documenting neurocognitive impairment in long-term survivors of childhood osteosarcoma. OBJECTIVE: To examine neurocognitive, neurobehavioral, emotional, and quality-of-life outcomes in long-term survivors of childhood osteosarcoma. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional cohort study at an academic research hospital, with prospective treatment and chronic health predictors. Outcome data were collected from June 2008 to August 2014. Data analysis was completed in April 2015. Survivors of osteosarcoma recruited from the St Jude Lifetime Cohort Study were compared with community controls. MAIN OUTCOMES AND MEASURES: Neurocognitive function, neurobehavioral symptoms, emotional distress, and quality of life. Outcomes were examined in relation to pharmacokinetic indices of methotrexate exposure and current chronic health conditions, which were assessed through medical examination and coded according to Common Terminology Criteria for Adverse Events, Version 4.03. RESULTS: Eighty survivors of osteosarcoma (mean [SD] age, 38.9 [7.6] years; time since diagnosis, 24.7 [6.6] years; 42% female) were compared with 39 community controls (age, 39.0 [11.7] years; 56% female). Survivors demonstrated lower mean scores in reading skills (-0.21 [95% CI, -0.32 to -0.10] vs 0.05 [95% CI, -0.13 to 0.23]; P = .01), attention (-0.78 [95% CI, -1.32 to -0.24] vs 0.24 [95% CI, -0.07 to 0.55]; P = .002), memory (-0.24 [95% CI, -0.48 to 0] vs 0.27 [95% CI, -0.08 to 0.62]; P = .01), and processing speed (-0.15 [95% CI, -0.35 to 0.05] vs 0.74 [95% CI, 0.44 to 1.03]; P < .001). Results of pharmacokinetic analysis showed that high-dose methotrexate maximum plasma concentration (estimate = 0; P = .48), median clearance (estimate = -0.11; P = .76), and median/cumulative exposure (estimate = 0; P = .45) were not associated with neurocognitive outcomes. Any grade 3 or 4 Common Terminology Criteria for Adverse Events cardiac, pulmonary, or endocrine condition was associated with poorer memory (t = 2.93; P = .006) and slower processing speed (t = 3.03; P = .002). Survivor-reported poor general health was associated with decreased sustained attention (estimate = 0.24; P = .05) and processing speed (estimate = 0.34; P = .005). CONCLUSIONS AND RELEVANCE: Long-term survivors of osteosarcoma are at risk for neurocognitive impairment, which is related to current chronic health conditions and not to original treatment with high-dose methotrexate. Prospective longitudinal studies are needed to identify onset and progression of impairment to inform optimal interventions.

Pharmacokinetic Properties of Anticancer Agents for the Treatment of Central Nervous System Tumors: Update of the Literature.

Despite significant improvement in outcomes for patients with hematologic malignancies and solid tumors over the past 10 years, patients with primary or metastatic brain tumors continue to have a poor prognosis. A primary reason for this is the inability of many chemotherapeutic drugs to penetrate into the brain and brain tumors at concentrations high enough to exert an antitumor effect because of unique barriers and efflux transporters. Several studies have been published recently examining the central nervous system pharmacokinetics of various anticancer drugs in patients with primary and metastatic brain tumors. To summarize recent advances in the field, this review critically presents studies published within the last 9 years examining brain and cerebrospinal fluid penetration of clinically available anticancer agents for patients with central nervous system tumors.

Determination of Methotrexate, 7-Hydroxymethotrexate, and 2,4-Diamino-N10-methylpteroic Acid by LC-MS/MS in Plasma and Cerebrospinal Fluid and Application in a Pharmacokinetic Analysis of High-Dose Methotrexate.

A rapid and robust method for measuring methotrexate (MTX) and its two primary metabolites, 7-hydroxymethotrexate (7-OHMTX) and 2,4-diamino-N10-methylpteroic acid (DAMPA), was developed for use in pharmacokinetic studies of plasma and cerebrospinal fluid samples collected from infants with malignant brain tumors. Sample aliquots (100µL) were prepared for bioanalysis of MTX and metabolites using a Waters Oasis HLB microelution SPE plate. Chromatography was performed using a Phenomenex Synergi Polar-RP 4µ 75 × 2.0mm ID column heated to 40°C. A rapid gradient elution on a Shimadzu HPLC system was used, with mobile phase A consisting of water/formic acid (100/0.1 v/v) and mobile phase B consisting of acetonitrile/formic acid (100/0.1 v/v). Column eluent was analyzed using AB Sciex QTRAP 5500 instrumentation in electrospray ionization mode. The ion transitions (m/z) monitored were 455.2→308.1, 471.1→324.1, and 326.2→175.1 for MTX, 7-OHMTX, and DAMPA respectively. The method was linear over a range of 0.0022 - 5.5 µM for MTX, 0.0085 - 21 µM for 7-OHMTX, and 0.0031 - 7.7 µM for DAMPA. The method was applied to the analysis of serial plasma samples obtained from infants diagnosed with malignant brain tumors receiving high-dose MTX and results were compared to MTX concentrations from a TDx-FLx FPIA.

Phase I study of 5-fluorouracil in children and young adults with recurrent ependymoma.

BACKGROUND: We report a phase I study to examine the pharmacokinetics, safety, and recommended dosage of weekly intravenous bolus 5-fluorouracil (5-FU) in children and young adults with recurrent ependymoma. METHODS: Patients 22 years of age or less with recurrent ependymoma were treated with bolus dosage 5-FU weekly for 4 weeks followed by a 2-week rest period, defining one cycle. Patients could continue on therapy for 16 cycles. The starting 5-FU dosage was 500 mg/m(2). Dose-limiting toxicity was determined after one cycle. Patients were initially enrolled according to a rolling-6 design; subsequent dose re-escalation phase was based on a 3 + 3 design. RESULTS: We treated patients at 400 (n = 6), 500 (n = 15), and 650 (n = 5) mg/m(2), with de-escalation due to toxicity. Twenty-three of twenty-six patients enrolled were evaluable. Five patients experienced grade 4 neutropenia (n = 2: 650 mg/m(2); n = 3: 500 mg/m(2)). One patient experienced grade 3 diarrhea. At 500 mg/m(2), the median 5-FU maximal concentration, AUC0-∞, and alpha half-life were 825 µM, 205 µM × h, and 9.9 min, respectively. Interim analysis revealed an association between hematologic toxicity and prior number of chemotherapeutic regimens (P = .03). The study was amended to re-escalate the dosage in a less heavily pretreated cohort of patients. CONCLUSIONS: These phase I clinical data provide initial pharmacokinetic parameters to describe i.v. bolus 5-FU disposition in children with recurrent ependymoma. Tumor exposures effective in preclinical testing can be achieved with tolerable bolus dosages in patients. Bolus 5-FU is well tolerated and possesses antitumor activity.

Phase I trial of weekly MK-0752 in children with refractory central nervous system malignancies: a pediatric brain tumor consortium study.

PURPOSE: Amplification and high levels of NOTCH ligand expression have been identified in several types of pediatric brain tumors. A phase I trial of weekly MK-0752, an oral inhibitor of gamma-secretase, was conducted in children with recurrent central nervous system (CNS) malignancies to estimate the maximum tolerated dose, dose-limiting toxicities (DLT), pharmacokinetics (PK), and pharmacodynamics of weekly MK-0752. METHODS: MK-0752 was administered once weekly at 1000 and 1400 mg/m(2) using a rolling-6 design. PK analysis was performed during the first course. NOTCH and HES expression was assessed by immunohistochemistry and Western blot. RESULTS: Ten eligible patients were enrolled (median age 8.8 years; range 3.1-19.2) with diagnoses of brain stem glioma (n = 3), ependymoma (n = 2), anaplastic astrocytoma (n = 1), choroid plexus carcinoma (n = 2), medulloblastoma (n = 1), and primitive neuroectodermal tumor (n = 1). Nine were evaluable for toxicity. One DLT of fatigue occurred in the six evaluable patients enrolled at 1000 mg/m(2)/dose. No DLTs were experienced by three patients treated at 1400 mg/m(2)/dose. Non-dose-limiting grade 3 toxicities included lymphopenia, neutropenia, and anemia. Median number of treatment courses was 2 (range 1-10). Two patients continued on therapy for at least 6 months. The median (range) C(max) of MK-0752 was 88.2 µg/mL (40.6 to 109 µg/mL) and 60.3 µg/mL (59.2 to 91.9 µg/mL) in patients receiving 1000 and 1400 mg/m(2)/week, respectively. NOTCH expression was decreased in six of seven patients for whom tissue was available at 24 h post-MK-0752. CONCLUSION: MK-0752 is well tolerated and exhibits target inhibition at 1000 and 1400 mg/m(2)/week in children with recurrent CNS malignancies.