Current Clinical Trials of Molecularly Targeted Agents in Children With Cancer, Part 2

A number of molecularly targeted agents directed atcritical cell survival and cell proliferation pathways have recently enteredclinical evaluation in children with cancer. These agents offer the potentialfor more effective anticancer therapy while simultaneously diminishing acute andlong-term toxic effects. Systematic evaluations of targeted agents are essentialto achieving continued improvements in outcome for children with cancer. Briefsummaries of the rationale for conducting studies of several agents in childrenare provided below. Following these summaries is a listing of phase I, phaseI/II, phase II, and pilot studies of these and other agents in pediatricpopulations.

Clinical Trials Referral Resource is designed to serve as a ready reference for oncologists to help identify clinical trials that might be suitable for their patients. We hope it will also enhance accrual to clinical trials by informing practicing oncologists of ongoing protocols. Currently in the United States less than 10% of eligible adult patients are entered into clinical trials. The result is a delay in answering important therapeutic and scientific questions and disseminating therapeutic advances to the general oncology community.

It should be emphasized that including a specific trial does not imply that it is more important than another trial. Among the criteria for selection are that the trial is addressing an important question and is not expected to close in the immediate future (less than 1 year), and that initial staging or laboratory tests required for patient eligibility are widely practiced and available. Information on other protocols can be accessed via Physician’s Data Query (PDQ).*

We emphasize that this is an attempt to encourage referral of patients to these trials. We are specifically not soliciting additional members for the cooperative groups, nor are we suggesting how practicing oncologists should be treating patients who are not in a study.

This month’s installment of Clinical Trials Referral Resource, a continuation of the article begun in the previous issue, is devoted to current clinical trials of molecularly targeted agents for children with cancer.

For patient entry information, see the individual trials.

* PDQ is a comprehensive database service provided by the National Cancer Institute’s International Cancer Information Center and Office of Cancer Communications for retrieval of cancer treatment information, including peer-reviewed statements on treatment options, supportive care, screening, and prevention; and an international clinical trials registry. For more information on PDQ, online access is available at www.cancer.gov/cancer_information/pdq/, or contact the Cancer Information Service offices (1-800-4-CANCER).

G3139

G3139 (bcl-2 antisense, Genasense) is an 18-mer phosphorothioateoligonucleotide antisense molecule that binds to the first six codons of humanbcl-2 mRNA and reduces expression of the bcl-2 gene by preventing translationand production of the encoded protein.[1] By reducing levels of bcl-2 protein,G3139 increases the activation of the apoptotic pathway in response to variousstimuli such as chemotherapy, irradiation, or other DNA-damaging events. Tumorxenograft models have demonstrated single-agent activity of G3139 againstfollicular lymphoma cell lines[1] and against a neuroendocrine malignancy (ie,Merkel cell carcinoma).[2] In xenograft models in which G3139 was tested incombination with chemotherapy, enhanced antitumor activity was observed forcyclophosphamide (Cytoxan, Neosar) against non-Hodgkin lymphoma,[3] fordacarabazine (DTIC-Dome) against melanoma,[4] and for cisplatin against gastriccarcinoma.[5]

G3139 has been studied in adults with cancer, both as a single agent[6] andin combination with chemotherapy.[7,8] Because antisense-mediateddown-regulation of bcl-2 levels requires several days, G3139 is administeredintravenously as a single agent for 4 to 7 days prior to the initiation ofchemotherapy.

G3139 has been generally well tolerated, and serum levels in excess of thoseassociated with bcl-2 down-regulation and potentiation of chemotherapy have beenachieved. Combinations of G3139 with chemotherapy have not produced substantialincreases in toxicity compared to those expected for chemotherapy alone.Down-regulation of bcl-2 in peripheral blood mononuclear cells and in tumorcells has been observed in adult studies.[6,8]

G3139 may eventually have utility against several pediatric cancers in whichbcl-2 may be associated with treatment resistance, includingneuroblastoma,[9,10] synovial sarcoma,[11,12] acute lymphoblasticleukemia,[13,14] and acute myeloid leukemia.[15,16] G3139 is being evaluated incombination with doxorubicin and cyclophosphamide in a pediatric solid tumorphase I study (ADVL0211) that should begin enrollment in the first quarter of2002.

ZD1839

ZD1839 (Iressa) is an orally available agent that selectively inhibits thetyrosine kinase activity of the epidermal growth factor receptor (EGFr).[17]ZD1839 inhibits ligand-induced EGFr autophosphorylation, leading generally to acytostatic effect.[17] In preclinical models, oral dosing occasionally causestumor regression but more generally causes growth inhibition of EGFr-expressingtumor xenografts.[18,19] The antitumor activity of a variety of conventionalchemotherapeutic agents can be potentiated when combined with ZD1839.[18,19]

Phase I trials of ZD1839 demonstrated that the agent is well tolerated atdoses that suppress EGFr phosphorylation in surrogate tissues.[20] When ZD1839is administered daily, the most common toxicities observed are grade 1/2diarrhea and a distinctive acneiform skin rash.[17] The pharmacokinetics ofZD1839 justify administration on a once-daily schedule. ZD1839 has inducedresponses in patients with colorectal, ovarian, non-small-cell lung cancer,head and neck, renal, and hormone-resistant prostate cancers.[17,21,22] It hasbeen safely combined with several conventional chemotherapy agents, includingcisplatin/gemcitabine (Gemzar)[23] and fluorouracil/leucovorin.[24] Another EGFrinhibitor, cetuximab (IMC-C225, Erbitux) has been safely administered incombination with cisplatin,[25,26] irinotecan (CPT-11, Camptosar),[27] andradiation therapy,[28] further supporting the feasibility of combining thisclass of agent with conventional anticancer treatments.

The expression of EGFr in neuroblastoma,[29,30] rhabdomyosarcoma,[29,31]osteosarcoma,[32] and glioma[33] provides the rationale for studying ZD1839 inchildren. A pediatric phase I trial of ZD1839 (ADVL0016) in children with solidtumors is scheduled to begin in the first quarter of 2002. For children withhigh-grade gliomas (either supratentorial or brainstem), the Pediatric BrainTumor Consortium is conducting a phase I study of ZD1839 in combination withradiation therapy (PBTC-007).

Rituximab

Rituximab (Rituxan) is a mouse/human chimeric antibody that targets the CD20antigen, which is present exclusively on B cells (pre-B and mature Blymphocytes) and on most B-cell lymphomas.[34,35] Rituximab kills cells viaseveral mechanisms, including antibody-dependent cellular toxicity, activationof the complement cascade,[36,37] and modulation of signaling pathways leadingto apoptosis.[38,39] In preclinical models, rituximab enhances the activity ofchemotherapy agents.[40-43]

Rituximab was first shown to be active against low-grade or follicularnon-Hodgkin lymphoma[44] and was subsequently found to be active against diffuselarge-cell lymphoma.[45] Toxicities attributed to rituximab are generally mildand most often associated with the first infusion. An acute tumor lysissyndrome, likely related to cytokine release, has occurred in patients with highcirculating lymphocyte count or large tumor burden.[46-48] Rituximab has beensafely combined with standard CHOP chemotherapy (cyclophosphamide, doxorubicinHCl, vincristine [Oncovin], prednisone),[49,50] with no substantial increase intoxicity above that associated with the CHOP regimen alone.

A randomized trial in elderly adults with diffuse large-cell lymphomacomparing CHOP to CHOP plus rituximab demonstrated significantly higherevent-free survival and survival rates in patients receiving rituximab pluschemotherapy.[51] Rituximab has also be been safely combined with an intensivechemotherapy regimen used to treat Burkitt lymphoma.[52]

Among the lymphomas that occur in children, diffuse large-cell lymphoma andBurkitt lymphoma both express high levels of CD20.[53-57] Rituximab inducesapoptosis in Burkitt lymphoma cell lines,[38,39] and anti-CD20 monoclonalantibodies are active in a Burkitt lymphoma xenograft model.[58] There areanecdotal reports of children with recurrent Burkitt lymphoma[59] and childrenwith post-transplant lymphoproliferative disease responding to rituximab.[60]

A Children’s Oncology Group pilot study (ANHL01P1) combining rituximab withstandard chemotherapy agents in children with newly diagnosed Burkitt lymphomaand diffuse large-cell lymphoma should begin accrual in the second quarter of2002. A second Children’s Oncology Group study (ANHL0121) will combinerituximab with ICE (ifosfamide [Ifex], carboplatin [Paraplatin], etoposide) inchildren with recurrent Burkitt lymphoma and diffuse large-cell lymphoma.Rituximab plus ICE chemotherapy has shown substantial activity in adults withrecurrent high-grade B-cell lymphomas.[61] The ANHL0121 study should open in thethird quarter of 2002.

IDEC-Y2B8

Yttrium-90-ibritumomab tiuxetan (IDEC-Y2B8, 90Y-Zevalin) is also to bestudied in children with recurrent B-cell lymphomas. Ibritumomab is a murineIgG1 kappa immunoglobulin that, like rituximab, reacts with the CD20 antigen. Itis covalently attached to the chelator tiuxetan, which can then secure eitherthe pure beta emitter yttrium-90 for therapeutic applications or secureindium-111 for imaging/dosimetry.[62]

A randomized trial in adults with relapsed or refractory low-grade,follicular, or CD20+ transformed B-cell non-Hodgkin lymphoma compared weeklyrituximab (four doses) to a regimen in which a single dose of IDEC-Y2B8 waspreceded by two doses of rituximab to clear peripheral B-cells and improvebiodistribution of IDEC-Y2B8.[62] Patients receiving IDEC-Y2B8 had a higherresponse rate compared to those receiving rituximab alone.[63] A pediatric phaseI study of IDEC-Y2B8 (ADVL0013) in children with recurrent B-cell lymphomasshould begin accruing patients in the third quarter of 2002.

In Summary

The clinical trials of the molecularly targeted agents described above andthose described in last month’s issue of Oncology represent necessary earlysteps towards rationalizing therapy for children with cancer. Realizing thepotential benefits of targeted therapies will require increased understanding ofthe biology of pediatric cancers, as well as systematic clinical evaluations oftargeted agents. Eventual success will require the concerted efforts ofmolecular biologists elucidating key survival and cell death pathways inspecific childhood cancers, of preclinical researchers using animal models toprioritize new agents for evaluation in children, and of clinicians implementingwell-conceived development plans for those agents selected for study inchildren.

Phase II

Title: A Phase II Study of Ifosfamide, Carboplatin, Etoposide, andRituximab as Retrieval Therapy for Relapsed/Refractory NHL—A COG Study
Protocol Number: ANHL0121
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116

Phase I/II

Title: A Phase I/II Trial of ZD1839 (Iressa) and Radiation in PediatricPatients Newly Diagnosed With Brain Stem Tumors or Incompletely ResectedSupratentorial Malignant Gliomas With Phase II Limited to Brain Stem Tumors
Protocol Number: PBTC-007
Participating Institutions: Pediatric Brain Tumor Consortium
Contact: J. Russell Geyer, (206) 526-2106

Phase I

Title: Phase I Study of Rituximab Followed By Yttrium Y 90Ibritumomab Tiuxetan With or Without Autologous Peripheral Blood Stem CellTransplantation in Children With Recurrent or Refractory CD20-Positive Lymphoma
Protocol Number: COG-ADVL0013
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116
Latest Information:http://www.cancer.gov/clinical_trials/

Title: A Phase I Study of ZD1839 (Iressa), an Oral Epidermal GrowthFactor Receptor Tyrosine Kinase Inhibitor, in Children With Refractory SolidTumors
Protocol Number: ADVL0016
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116

Title: A Phase I Trial of BCL-2 Antisense Combined With CytotoxicChemotherapy in Relapsed Childhood Solid Tumors
Protocol Number: ADVL0211
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116

Pilot Studies

Title: A Pilot Study to Determine the Toxicity of the Addition ofRituximab to the Induction and Consolidation Phases and the Addition ofRasburicase to the Reduction Phase in Children With Newly Diagnosed AdvancedB-Cell Leukemia/Lymphoma Treated with LMB/FAB Therapy
Protocol Number: ANHL01P1
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116

Other Agents of Interest in Clinical Trials

Title: Phase II Study of Gemcitabine in Children With Relapsed orRefractory AcuteLymphoblastic Leukemia or Acute Myelogenous Leukemia
Protocol Number: CCG-A0999, COG-ADVL0022
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116; for a complete listingof study contacts, click hereLatest Information:http://www.cancer.gov/clinical_trials/

Title: Phase II Study of Compound 506U78 in Patients with RefractoryT-Cell Malignancies
Protocol Number: CCG-P9673, POG-9673
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116; for a complete listingof study contacts, click hereLatest Information:http://www.cancer.gov/clinical_trials/

Title: Phase II Study of Rebeccamycin Analogue in Children WithSolid Tumors or Non-Hodgkin's Lymphoma
Protocol Number: COG-P9963
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116; for a complete listingof study contacts, click hereLatest Information:http://www.cancer.gov/clinical_trials/

Title: Phase I Study of Flavopiridol in Children With Relapsed orRefractory Solid Tumors or Lymphomas
Protocol Number: CCG-AO972, COG-ADVL0017, NCI-A0972
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116; for a complete listingof study contacts, click hereLatest Information:http://www.cancer.gov/clinical_trials/

Title: Phase I Study of hu14.18-Interleukin-2 Fusion Protein inChildren With Refractory or Recurrent Neuroblastoma or Other GD2-Positive Tumors
Protocol Number: ADVL0018
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116; for a complete listingof study contacts, click hereLatest Information:http://www.cancer.gov/clinical_trials/

Title: Phase II Pilot Study of Modified MultiagentBerlin-Frankfurt-Muenster-86 Chemotherapy With or Without 506U78 in PatientsWith Newly Diagnosed T-Cell Acute Lymphoblastic Leukemia
Protocol Number: COG-AALL00P2
Participating Institutions: Children’s Oncology Group
Contact: Judith Everett, (626) 447-0064, ext 116; for a complete listingof study contacts, click hereLatest Information:http://www.cancer.gov/clinical_trials/

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