Treatment of relapsed/refractory severe aplastic anemia in children: Evidence-based recommendations.

Severe aplastic anemia (SAA) is a rare potentially fatal hematologic disorder. Although overall outcomes with treatment are excellent, there are variations in management approach, including differences in treatment between adult and pediatric patients. Certain aspects of treatment are under active investigation in clinical trials. Because of the rarity of the disease, some pediatric hematologists may have relatively limited experience with the complex management of SAA. The following recommendations reflect an up-to-date evidence-based approach to the treatment of children with relapsed or refractory SAA.

Treatment of newly diagnosed severe aplastic anemia in children: Evidence-based recommendations.

Severe aplastic anemia (SAA) is a rare potentially fatal hematologic disorder. Although overall outcomes with treatment are excellent, there are variations in management approach, including differences in treatment between adult and pediatric patients. Certain aspects of treatment are under active investigation in clinical trials. Because of the rarity of the disease, some pediatric hematologists may have relatively limited experience with the complex management of SAA. The following recommendations reflect an up-to-date evidence-based approach to the treatment of children with newly diagnosed SAA.

Diagnostic work-up for severe aplastic anemia in children: Consensus of the North American Pediatric Aplastic Anemia Consortium.

The North American Pediatric Aplastic Anemia Consortium (NAPAAC) is a group of pediatric hematologist-oncologists, hematopathologists, and bone marrow transplant physicians from 46 institutions in North America with interest and expertise in aplastic anemia, inherited bone marrow failure syndromes, and myelodysplastic syndromes. The NAPAAC Bone Marrow Failure Diagnosis and Care Guidelines Working Group was established with the charge of harmonizing the approach to the diagnostic workup of aplastic anemia in an effort to standardize best practices in the field. This document outlines the rationale for initial evaluations in pediatric patients presenting with signs and symptoms concerning for severe aplastic anemia.

A POETIC Phase II study of continuous oral everolimus in recurrent, radiographically progressive pediatric low-grade glioma.

BACKGROUND: To evaluate efficacy, pharmacokinetics (PK) and pharmacodynamics of single-agent everolimus in pediatric patients with radiographically progressive low-grade glioma (LGG). METHODS: Everolimus was administered at 5 mg/m2 once daily as a tablet or liquid for a planned 48-week duration or until unacceptable toxicity or disease progression. Patients with neurofibromatosis type 1 were excluded. PK and pharmacodynamic endpoints were assessed in consenting patients. RESULTS: Twenty-three eligible patients (median age 9.2 years) were enrolled. All patients received prior chemotherapy (median number of prior regimens two) and/or radiotherapy (two patients). By week 48, two patients had a partial response, 10 stable disease, and 11 clinical or radiographic progression; two discontinued study prior to 1 year (toxicity: 1, physician determination: 1). With a median follow up of 1.8 years (range 0.2-6.7 years), the 2-, 3-, and 5-year progression-free survivals (PFS) were 39 ± 11%, 26 ± 11%, and 26 ± 11%, respectively; two patients died of disease. The 2-, 3-, and 5-year overall survival (OS) were all 93 ± 6%. Grade 1 and 2 toxicities predominated; two definitively related grade 3 toxicities (mucositis and neutropenia) occurred. Grade 4 elevation of liver enzymes was possibly related in one patient. Predose blood levels showed substantial variability between patients with 45.5% below and 18.2% above the target range of 5-15 ng/mL. Pharmacodynamic analysis demonstrated significant inhibition in phospho-S6, 4E-BP1, and modulation of c-Myc expression. CONCLUSION: Daily oral everolimus provides a well-tolerated, alternative treatment for multiple recurrent, radiographically progressive pediatric LGG. Based on these results, everolimus is being investigated further for this patient population.

Dual functionality of the antimicrobial agent taurolidine which demonstrates effective anti-tumor properties in pediatric neuroblastoma.

High-risk, relapsed and refractory neuroblastoma are associated with poor 5-years survival rates, demonstrating the need for investigational therapeutic agents to treat this disease. Taurolidine is derived from the aminosulfoacid taurine and has known anti-microbial and anti-inflammatory properties. Taurolidine has also demonstrated anti-neoplastic effects in a range of cancers, providing the rationale to investigate the activity of taurolidine against neuroblastoma in preclinical studies. We investigated the in vitro activity of taurolidine against neuroblastoma using the alamar blue cytotoxicity assay, phase-contrast light microscopy, western blotting and analysis of global gene expression by RNA-Seq. In vivo activity of taurolidine was evaluated using mouse xenograft models. In vitro pre-clinical data show that taurolidine is cytotoxic to neuroblastoma cell lines, inducing cell death by apoptosis. Analysis of global gene expression and determination of signaling pathway activation scores using the in silico Pathway Activation Network Decomposition Analysis (iPANDA) platform indicates that taurolidine has an effect on the Notch, mitogen-activated protein kinase (MAPK) and interleukin-10 (IL-10) signaling pathways. In vivo experiments in xenograft mouse models show that taurolidine decreases tumor growth and improves survival. These results provide supportive pre-clinical data on the activity of taurolidine against neuroblastoma. The findings support the rationale for further evaluation of taurolidine for the treatment of relapsed/refractory neuroblastoma patients in an early phase clinical trial.

Results from an international phase 2 study of the anti-CD22 immunotoxin moxetumomab pasudotox in relapsed or refractory childhood B-lineage acute lymphoblastic leukemia.

BACKGROUND: In a multicenter phase 1 study of children with relapsed/refractory acute lymphoblastic leukemia (ALL), moxetumomab pasudotox, an anti-CD22 immunotoxin, demonstrated a manageable safety profile and preliminary evidence of clinical activity. A phase 2 study further evaluated efficacy. PROCEDURE: This international, multicenter, phase 2 study enrolled children with relapsed/refractory B-cell precursor ALL who received moxetumomab pasudotox 40 µg/kg intravenously every other day, for six doses per 21-day cycle. The primary objective was to evaluate the complete response (CR) rate. Secondary objectives included safety, pharmacokinetics, and immunogenicity evaluations. RESULTS: Thirty-two patients (median age, 10 years) were enrolled at 16 sites; 30 received study drug and were evaluable for safety; 28 were evaluable for response. The objective response rate was 28.6%, with three patients (10.7%) achieving morphologic CR, and five patients (17.9%) achieving partial response. Disease progression occurred in 11 patients (39.3%). Ten patients (33.3%) experienced at least one treatment-related serious adverse event, including capillary leak syndrome (CLS; n = 6), hemolytic uremic syndrome (HUS; n = 4), and treatment-related death (n = 1) from pulmonary edema. No differences were observed in inflammatory markers in patients who did or did not develop CLS or HUS. CONCLUSIONS: Despite a signal for clinical activity, this phase 2 study was terminated at interim analysis for a CR rate that did not reach the stage 1 target. Preclinical data suggest enhanced efficacy of moxetumomab pasudotox via continuous infusion or in combination regimens; thus, further studies designed to optimize the efficacy and safety of moxetumomab pasudotox in pediatric ALL may be warranted.

Outcomes of Hematopoietic Cell Transplantation in Patients with Germline SAMD9/SAMD9L Mutations.

Germline mutations in SAMD9 and SAMD9L genes cause MIRAGE (myelodysplasia, infection, restriction of growth, adrenal hypoplasia, genital phenotypes, and enteropathy) (OMIM: *610456) and ataxia-pancytopenia (OMIM: *611170) syndromes, respectively, and are associated with chromosome 7 deletions, myelodysplastic syndrome (MDS), and bone marrow failure. In this retrospective series, we report outcomes of allogeneic hematopoietic cell transplantation (HCT) in patients with hematologic disorders associated with SAMD9/SAMD9L mutations. Twelve patients underwent allogeneic HCT for MDS (n = 10), congenital amegakaryocytic thrombocytopenia (n = 1), and dyskeratosis congenita (n = 1). Exome sequencing revealed heterozygous mutations in SAMD9 (n = 6) or SAMD9L (n = 6) genes. Four SAMD9 patients had features of MIRAGE syndrome. Median age at HCT was 2.8 years (range, 1.2 to 12.8 years). Conditioning was myeloablative in 9 cases and reduced intensity in 3 cases. Syndrome-related comorbidities (diarrhea, infections, adrenal insufficiency, malnutrition, and electrolyte imbalance) were present in MIRAGE syndrome cases. One patient with a familial SAMD9L mutation, MDS, and morbid obesity failed to engraft and died of refractory acute myeloid leukemia. The other 11 patients achieved neutrophil engraftment. Acute post-transplant course was complicated by syndrome-related comorbidities in MIRAGE cases. A patient with SAMD9L-associated MDS died of diffuse alveolar hemorrhage. The other 10 patients had resolution of hematologic disorder and sustained peripheral blood donor chimerism. Ten of 12 patients were alive with a median follow-up of 3.1 years (range, 0.1 to 14.7 years). More data are needed to refine transplant approaches in SAMD9/SAMD9L patients with significant comorbidities and to develop guidelines for their long-term follow-up.

Immunosuppressive therapy for pediatric aplastic anemia: a North American Pediatric Aplastic Anemia Consortium study.

Quality of response to immunosuppressive therapy and long-term outcomes for pediatric severe aplastic anemia remain incompletely characterized. Contemporary evidence to inform treatment of relapsed or refractory severe aplastic anemia for pediatric patients is also limited. The clinical features and outcomes for 314 children treated from 2002 to 2014 with immunosuppressive therapy for acquired severe aplastic anemia were analyzed retrospectively from 25 institutions in the North American Pediatric Aplastic Anemia Consortium. The majority of subjects (n=264) received horse anti-thymocyte globulin (hATG) plus cyclosporine (CyA) with a median 61 months follow up. Following hATG/CyA, 71.2% (95%CI: 65.3,76.6) achieved an objective response. In contrast to adult studies, the quality of response achieved in pediatric patients was high, with 59.8% (95%CI: 53.7,65.8) complete response and 68.2% (95%CI: 62.2,73.8) achieving at least a very good partial response with a platelet count ≥50×109L. At five years post-hATG/CyA, overall survival was 93% (95%CI: 89,96), but event-free survival without subsequent treatment was only 64% (95%CI: 57,69) without a plateau. Twelve of 171 evaluable patients (7%) acquired clonal abnormalities after diagnosis after a median 25.2 months (range: 4.3-71 months) post treatment. Myelodysplastic syndrome or leukemia developed in 6 of 314 (1.9%). For relapsed/refractory disease, treatment with a hematopoietic stem cell transplant had a superior event-free survival compared to second immunosuppressive therapy treatment in a multivariate analysis (HR=0.19, 95%CI: 0.08,0.47; P=0.0003). This study highlights the need for improved therapies to achieve sustained high-quality remission for children with severe aplastic anemia.

Targeted Polo-like Kinase Inhibition Combined With Aurora Kinase Inhibition in Pediatric Acute Leukemia Cells.

BACKGROUND: Recent studies have shown that cell cycle events are tightly controlled by complex and shared activities of a select group of kinases. Among these, polo-like kinases (Plks) are regulatory mitotic proteins that are overexpressed in several types of cancer and are associated with poor prognosis. MATERIALS AND METHODS: We have evaluated, in preclinical in vitro studies, the activity of a panel of Plk inhibitors against cell lines derived from refractory pediatric leukemia, as well as primary leukemia cells, in culture. Through in vitro growth inhibition studies, Western blot analysis for the expression and activation of key regulators of cell growth and survival and gene silencing studies, we specifically examined the ability of these agents to induce cytotoxicity through the activation of apoptosis and their capacity to interact and modulate the expression and phosphorylation of Aurora kinases. RESULTS: Our findings show that the various Plk-1 inhibitors in development show potential utility for the treatment of pediatric leukemia and exhibit a wide range of phosphorylation and target modulatory capabilities. Finally, we provide evidence for a complex interregulatory relationship between Plk-1 and Aurora kinases enabling the identification of synergy and biologic correlates of drug combinations targeting the 2 distinct enzyme systems. DISCUSSION: This information provide the rationale for the evaluation of Plk-1 as an effective target for therapeutics in refractory pediatric leukemia and indicate compensatory activities between Plk-1 and Aurora kinases, providing insight into some of the complex mechanisms involved in the process of cell division.

Constitutional SAMD9L mutations cause familial myelodysplastic syndrome and transient monosomy 7.

Familial myelodysplastic syndromes arise from haploinsufficiency of genes involved in hematopoiesis and are primarily associated with early-onset disease. Here we describe a familial syndrome in seven patients from four unrelated pedigrees presenting with myelodysplastic syndrome and loss of chromosome 7/7q. Their median age at diagnosis was 2.1 years (range, 1-42). All patients presented with thrombocytopenia with or without additional cytopenias and a hypocellular marrow without an increase of blasts. Genomic studies identified constitutional mutations (p.H880Q, p.R986H, p.R986C and p.V1512M) in the SAMD9L gene on 7q21, with decreased allele frequency in hematopoiesis. The non-random loss of mutated SAMD9L alleles was attained via monosomy 7, deletion 7q, UPD7q, or acquired truncating SAMD9L variants p.R1188X and p.S1317RfsX21. Incomplete penetrance was noted in 30% (3/10) of mutation carriers. Long-term observation revealed divergent outcomes with either progression to leukemia and/or accumulation of driver mutations (n=2), persistent monosomy 7 (n=4), and transient monosomy 7 followed by spontaneous recovery with SAMD9L-wildtype UPD7q (n=2). Dysmorphic features or neurological symptoms were absent in our patients, pointing to the notion that myelodysplasia with monosomy 7 can be a sole manifestation of SAMD9L disease. Collectively, our results define a new subtype of familial myelodysplastic syndrome and provide an explanation for the phenomenon of transient monosomy 7. Registered at: www.clinicaltrials.gov; #NCT00047268.

A phase 1/2 dose-finding, safety, and activity study of cabazitaxel in pediatric patients with refractory solid tumors including tumors of the central nervous system.

BACKGROUND: This phase 1/2 study (NCT01751308) evaluated cabazitaxel in pediatric patients. Phase 1 determined the maximum tolerated dose (MTD) in patients with recurrent/refractory solid tumors, including central nervous system (CNS) tumors. Phase 2 evaluated activity in pediatric recurrent high-grade glioma (HGG) or diffuse intrinsic pontine glioma (DIPG). PROCEDURE: In phase 1, a 3 + 3 dose-escalation study design was followed. Cabazitaxel was administered at a starting dose of 20 mg/m2 . Dose-limiting toxicities (DLTs) during cycle 1 were assessed to determine the MTD. Tumor response and cabazitaxel pharmacokinetics were also assessed. In phase 2, patients received cabazitaxel at the MTD determined in phase 1. Tumor responses were assessed every 9 weeks (modified Response Assessment in Neuro-oncology criteria). Progression-free survival and cabazitaxel pharmacokinetics were evaluated, and overall survival was estimated. RESULTS: In phase 1, 23 patients were treated, including 19 with CNS tumors. One patient had a partial response; five had stable disease for >3 cycles. Common adverse events included fatigue, diarrhea, nausea and vomiting, febrile neutropenia, and hypersensitivity reactions. Two of three DLTs (febrile neutropenia) occurred with a dose of 35 mg/m2 ; the MTD was 30 mg/m2 . Slightly higher cabazitaxel clearance was observed compared with adult trials. In phase 2, 16 patients (eight HGG and eight DIPG) were enrolled; 11 were evaluable for response and five withdrew (three due to anaphylaxis). All 11 patients progressed within four cycles. No responses were observed; the study was stopped due to futility. CONCLUSIONS: The safety profile of cabazitaxel was consistent with previous studies. The MTD (30 mg/m2 ) was higher than the adult MTD. Cabazitaxel did not demonstrate activity in recurrent/refractory HGG or DIPG.

Pediatric Chronic Myeloid Leukemia Presenting With Extreme Thrombocytosis Simulating Essential Thrombocythemia.

A 10-year-old boy presented with spontaneous bruising and was found to have extreme thrombocytosis without neutrophilia/shift to immaturity, basophilia or eosinophilia. While the peripheral blood and bone marrow findings initially suggested essential thrombocythemia, BCR-ABL1 translocation was detected and chronic myeloid leukemia, chronic phase, was diagnosed. Apheresis for platelet depletion was performed as a bridge given the delayed effects of medical therapy.

A phase 1 study of the CXCR4 antagonist plerixafor in combination with high-dose cytarabine and etoposide in children with relapsed or refractory acute leukemias or myelodysplastic syndrome: A Pediatric Oncology Experimental Therapeutics Investigators' Consortium study (POE 10-03).

BACKGROUND: Plerixafor, a reversible CXCR4 antagonist, inhibits interactions between leukemic blasts and the bone marrow stromal microenvironment and may enhance chemosensitivity. A phase 1 trial of plerixafor in combination with intensive chemotherapy in children and young adults with relapsed or refractory acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and myelodysplastic syndrome (MDS) was performed to determine a tolerable and biologically active dose. PROCEDURE: Plerixafor was administered daily for 5 days at four dose levels (6, 9, 12, and 15 mg/m2 /dose) followed 4 hr later by high-dose cytarabine (every 12 hr) and etoposide (daily). RESULTS: Nineteen patients (13 with AML, 5 with ALL, 1 with MDS) were treated. The most common grade 3 or greater nonhematologic toxicities attributable to plerixafor were febrile neutropenia and hypokalemia. There were no dose-limiting toxicities (DLTs). Plerixafor exposure increased with increasing dose levels and clearance was similar on days 1 and 5. Eighteen patients were evaluable for response. Two patients achieved complete remission (CR) and one patient achieved CR with incomplete hematologic recovery (CRi): all three had AML. No responses were seen in patients with ALL or MDS. Plerixafor mobilized leukemic blasts into the peripheral blood in 14 of 16 evaluable patients (median 3.4-fold increase), and the degree of mobilization correlated with surface CXCR4 expression. CONCLUSIONS: Plerixafor, in combination with high-dose cytarabine and etoposide, was well tolerated in children and young adults with relapsed/refractory acute leukemias and MDS. While biologic responses were observed, clinical responses in this heavily pretreated cohort were modest.

Combination of clofarabine, cyclophosphamide, and etoposide for relapsed or refractory childhood and adolescent acute myeloid leukemia.

Relapsed/refractory acute myeloid leukemia (AML) has an extremely poor prognosis. We describe 17 children and adolescents with relapsed/refractory AML who received clofarabine, cyclophosphamide, and etoposide. Seven patients (41%) responded: 4 with a complete response (CR); 1 with CR with incomplete platelet recovery; and 2 with a partial response. Additionally, 4 developed hypocellular marrow without evidence of leukemia; 5 patients had resistant disease; and 1 suffered early toxic death. After further therapy including transplantation, 4 patients (24%) are alive without evidence of disease at a median of 60 months. This anthracycline-free regimen may be studied for relapsed or refractory AML, but due to the high risk of marrow aplasia reduced doses of clofarabine and cyclophosphamide should be used.

A multi-center phase Ib study of oxaliplatin (NSC#266046) in combination with fluorouracil and leucovorin in pediatric patients with advanced solid tumors.

BACKGROUND: Platinum agents have been used for a variety of cancers, including pivotal use in pediatric tumors for many years. Oxaliplatin, a third generation platinum, has a different side effect profile and may provide improved activity in pediatric cancers. PROCEDURE: Patients 21 years or younger with progressive or refractory malignant solid tumors, including tumors of the central nervous system were enrolled on this multi-center open label, non-randomized Phase 1 dose escalation study. The study used a standard 3 + 3 dose escalation design with 2 dose levels (85 and 100 mg/m(2) ) with an expansion cohort of 15 additional patients at the recommended dose. Patients received oxaliplatin at the assigned dose level and 5-fluorouracil (5-FU) bolus 400 mg/m(2) followed by a 46-hour 5-FU infusion of 2,400 mg/m(2) every 14 days. The leucovorin dose was fixed at 400 mg/m(2) for all cohorts. RESULTS: Thirty-one evaluable patients were enrolled, 8 at 85 mg/m(2) and 23 at 100 mg/m(2) for a total of 121 courses. The median age was 12 years (range 2-19 years). The main toxicities were hematologic, primarily neutrophils and platelets. The most common non-hematologic toxicities were gastrointestinal. Stable disease was noted in 11 patients (54% of evaluable patients) and 1 confirmed partial response in a patient with osteosarcoma. CONCLUSIONS: The maximum planned dose of oxaliplatin at 100 mg/m(2) per dose in combination with 5-FU and leucovorin was safe and well tolerated and in this patient population. This combination demonstrated modest activity in patients with refractory or relapsed solid tumor and warrants further study. Pediatr Blood Cancer 2013;60:230-236. © 2012 Wiley Periodicals, Inc.

Phase I dose-escalation trial of clofarabine followed by escalating doses of fractionated cyclophosphamide in children with relapsed or refractory acute leukemias.

BACKGROUND: By inhibiting DNA repair, clofarabine (CLO) may augment cyclophosphamide (CY)-induced DNA damage and apoptosis. We performed a Phase I study for refractory and/or relapsed (R/R) leukemia in children to determine maximum-tolerated dose (MTD) of time-sequential CLO followed by CY. PROCEDURE: Thirteen patients with (R/R) ALL (n = 8) and AML (N = 5), median age 9 years (range: 2-12 years), were treated with escalating doses of CLO on days 1, 2, 3 and 8, 9, 10 and CY 200 mg/m(2) /day on days 0 and 1 then 400 mg/m(2) /day on days 2, 3, 8, 9, and 10. Ten patients were treated at dose level 1 (DL1) (CLO 20 mg/m(2) /day) and three patients at DL2 (CLO 30 mg/m(2) /day). The average number of prior chemotherapies was 8.9. DNA damage testing was performed before treatment on day 0, and 2 hours after CY on day 0, before sequential CLO, CY treatment on day 1, and 2 hours after CLO followed by CY on day 1. RESULTS: Two patients at DL2 had dose-limiting toxicities (DLTs) that included hypotension with cardio-respiratory failure (1) and hepato-renal failure (1). Complete remission (CR) was achieved in 2/11 (18.2%) and partial remission (PR) in 2/11 (18.2%) for an overall response (OR) of 36.4%. The use of CLO before CY augmented CY-induced DNA damage in leukemic blasts compared to CY alone. CONCLUSION: In pediatric patients with R/R leukemia, 20 mg/m(2) /day is the MTD for CLO in timed sequential combination with CY. Increased DNA damage with the use of this combination suggests a mechanism for the sequential timing of these two chemotherapeutic agents.

Cytotoxicity and Target Modulation in Pediatric Solid Tumors by the Proteasome Inhibitor Carfilzomib.

BACKGROUND: Most children with recurrent metastatic solid tumors have high mortality rates. Recent studies have shown that proteasome inhibition leads to effective tumor killing in cells that have acquired treatment resistance and metastatic properties. OBJECTIVE: The purpose of this study was to test the potential of Carfilzomib (CFZ), a proteasome inhibitor, in refractory pediatric solid tumors which is currently unknown. METHODS: A panel of pediatric solid tumor cell lines, including neuroblastoma, Ewing's sarcoma, osteosarcoma, rhabdomyosarcoma and atypical teratoid rhabdoid tumor (ATRT), was used to evaluate the cytotoxic and proteasomal inhibitory effects of CFZ. A drug scheduling experiment was performed to determine the optimal dose and time to obtain effective cell killing. Combination studies of CFZ with chemotherapeutic drugs of different classes were performed to determine the extent of synergy. RESULTS: CFZ showed effective cytotoxicity against all cell lines tested (mean IC50 = 7nM, range = 1-20nM) and activity in a fluorophore-tagged cell-based proteasome assay. Drug scheduling experiments showed that the minimum exposure of 4-8 hours/day is needed for effective cumulative killing. CFZ, when combined with chemotherapeutic drugs of different classes, synergistically enhanced the extent of cell death. CONCLUSION: CFZ showed cytotoxic activity against all the solid pediatric cancer cell lines tested. This study provides initial in vitro data on the potential of CFZ to treat pediatric solid tumors and supports further investigations into the components of drug scheduling, biological correlates and drug combinations for future early phase clinical trials in children.

Potentiation of reactive oxygen species is a marker for synergistic cytotoxicity of MS-275 and 5-azacytidine in leukemic cells.

Epigenetic modifiers are currently in clinical use for various tumor types. Recently, numerous studies supporting the combination of histone deacetylase inhibitors (HDACi) and DNA methyltransferase inhibitors have emerged, encouraging early clinical trials of these agents together. Here we show that MS-275, an HDACi, and 5-azacytidine, a methyltransferase inhibitor, display synergistic cytotoxicity and apoptosis in AML and ALL cells. Intracellular production of reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, is a novel marker for this synergism in ALL cells. These data suggest that assessment of oxidative stress can serve as a marker of the concerted action of MS-275 and 5-azacytidine.

Phase I pharmacokinetic and pharmacodynamic study of 17-N-allylamino-17-demethoxygeldanamycin in pediatric patients with recurrent or refractory solid tumors: a pediatric oncology experimental therapeutics investigators consortium study.

PURPOSE: Heat shock protein 90 (Hsp90) is essential for the posttranslational control of many regulators of cell growth, differentiation, and apoptosis. 17-N-Allylamino-17-demethoxygeldanamycin (17-AAG) binds to Hsp90 and alters levels of proteins regulated by Hsp90. We conducted a phase I trial of 17-AAG in pediatric patients with recurrent or refractory neuroblastoma, Ewing's sarcoma, osteosarcoma, and desmoplastic small round cell tumor to determine the maximum tolerated dose, define toxicity and pharmacokinetic profiles, and generate data about molecular target modulation. EXPERIMENTAL DESIGN: Escalating doses of 17-AAG were administered i.v. over 1 to 2 h twice weekly for 2 weeks every 21 days until patients experienced disease progression or toxicity. harmacokinetic and pharmacodynamic studies were done during cycle 1. RESULTS: Fifteen patients were enrolled onto dose levels between 150 and 360 mg/m(2); 13 patients were evaluable for toxicity. The maximum tolerated dose was 270 mg/m(2). DLTs were grade 3 transaminitis and hypoxia. Two patients with osteosarcoma and bulky pulmonary metastases died during cycle 1 and were not evaluable for toxicity. No objective responses were observed. 17-AAG pharmacokinetics in pediatric patients were linear; clearance and half-life were 21.6 +/- 6.21 (mean +/- SD) L/h/m(2) and 2.6 +/- 0.95 h, respectively. Posttherapy increases in levels of the inducible isoform of Hsp70, a marker of target modulation, were detected in peripheral blood mononuclear cells at all dose levels. CONCLUSION: 17-AAG was well tolerated at a dose of 270 mg/m(2) administered twice weekly for 2 of 3 weeks. Caution should be used in treatment of patients with bulky pulmonary disease.

Targeting the Proteasome in Refractory Pediatric Leukemia Cells: Characterization of Effective Cytotoxicity of Carfilzomib.

BACKGROUND: Leukemia accounts for 30% of all childhood cancers and although the survival rate for pediatric leukemia has greatly improved, relapse is a major cause of treatment failure. Therefore, the development and introduction of novel therapeutics to treat relapsed pediatric leukemia is urgently needed. The proteasome inhibitor bortezomib has been shown to be effective against adult hematological malignancies such as multiple myeloma and lymphoma, but is frequently associated with the development of resistance. Carfilzomib is a next-generation proteasome inhibitor that has shown promising results against refractory adult hematological malignancies. OBJECTIVE: Carfilzomib has been extensively studied in adult hematological malignancies, providing the rationale for evaluating proof-of-concept activity of carfilzomib in pediatric leukemia. METHODS: The effects of carfilzomib on pediatric leukemia cell lines and primary pediatric leukemia patient samples were investigated in vitro using the alamar blue cytotoxicity assay, western blotting, and a proteasome activity assay. Synergy with commonly used anticancer drugs was determined by calculation of combination indices. RESULTS: In vitro preclinical data show pharmacologically relevant concentrations of carfilzomib are cytotoxic to pediatric leukemia cell lines and primary pediatric leukemia cells. Target modulation studies validate the effective inhibition of the proteasome and induction of apoptosis. We also identify agents that have effective synergy with carfilzomib in these cells. CONCLUSIONS: Our data provide pre-clinical information that can be incorporated into future early-phase clinical trials for the assessment of carfilzomib as a treatment for children with refractory hematological malignancies.