Long-term, continuous infusion of single-agent dinutuximab beta for relapsed/refractory neuroblastoma: an open-label, single-arm, Phase 2 study

BACKGROUND

Short-term infusions of dinutuximab beta plus isotretinoin and cytokines administered in previous immunotherapy studies in neuroblastoma were associated with severe pain. Here, long-term, continuous infusion of single-agent dinutuximab beta was evaluated in patients with relapsed/refractory neuroblastoma.

METHODS

In this open-label, single-arm, Phase 2 study, patients with either refractory or relapsed high-risk neuroblastoma received dinutuximab beta by continuous infusion over 10 days of each cycle, for up to five cycles. The primary endpoint was objective response rate 24 weeks after the end of cycle 5. Secondary endpoints included adverse events, intravenous morphine use, best response, duration of response, and three-year progression-free and overall survival.

RESULTS

Of the 40 patients included, 38 had evaluable response. Objective response rate was 26% and best response rate 37%. Median duration of response was 238 days (IQR 108-290). Three-year progression-free and overall survival rates were 31% (95% CI 17-47) and 66% (95% CI 47-79), respectively. Prophylactic intravenous morphine use and duration of use decreased with increasing cycles. The most common grade 3 treatment-related adverse events were pain, diarrhea, and hypokalemia.

CONCLUSION

Long-term continuous infusion of single-agent dinutuximab beta is tolerable and associated with clinically meaningful responses in patients with relapsed/refractory high-risk neuroblastoma.

CLINICAL TRIAL REGISTRATION

The study is registered with ClinicalTrials.gov (NCT02743429) and EudraCT (2014-000588-42).

Effect and Tolerance of N5 and N6 Chemotherapy Cycles in Combination with Dinutuximab Beta in Relapsed High-Risk Neuroblastoma Patients Who Failed at Least One Second-Line Therapy

The anti-disialoganglioside (GD2) monoclonal antibody dinutuximab beta is approved for the maintenance treatment of high-risk neuroblastoma. Dinutuximab beta combined with different chemotherapy regimens is being investigated in various clinical settings. We conducted a retrospective clinical chart review of 25 patients with relapsed/refractory neuroblastoma who had failed ≥1 second-line therapy and received compassionate use treatment with dinutuximab beta long-term infusion combined with the induction chemotherapy regimens N5 (cisplatin, etoposide, vindesine) and N6 (vincristine, dacarbazine, ifosfamide, doxorubicin) recommended by the German Pediatric Oncology and Hematology Group [GPOH] guidelines. The treatment did not result in any unexpected severe toxicities or in any major treatment delays. Grade 3/4 pain was reported by 4/25 patients in cycle 1, decreasing to 0/9 patients in cycles 3 and 4. The median follow-up was 0.6 years. The best response in this group was 48% (12/25 patients), which included three patients with minor responses. At 1 year, the estimated event-free survival was 27% (95% confidence interval [CI] 8-47) and overall survival was 44% (95% CI 24-65). Combining long-term infusion of dinutuximab beta with N5 and N6 chemotherapy demonstrated an acceptable safety profile and encouraging objective response rates in heavily pretreated patients with high-risk neuroblastoma, warranting further evaluation in clinical trials.

Combined Blockade of TIGIT and PD-L1 Enhances Anti-Neuroblastoma Efficacy of GD2-Directed Immunotherapy with Dinutuximab Beta

Immunotherapies against high-risk neuroblastoma (NB), using the anti-GD2 antibody (Ab) dinutuximab beta (DB), significantly improved patient survival. Ab-dependent cellular cytotoxicity (ADCC) is one of the main mechanisms of action and it is primarily mediated by NK cells. To further improve antitumor efficacy, we investigated here a combinatorial immunotherapy with DB and the double immune checkpoint blockade of T-cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT) and programmed cell death ligand-1 (PD-L1). The effects of ADCC, mediated by DB against NB cells on NK-cell activity, and the expression of TIGIT and CD226 and their ligands CD112 and CD155, as well as of PD-1 and PD-L1 on NB and effector cells, were investigated using flow cytometry. ADCC was assessed with a calcein-AM-based cytotoxicity assay. The efficacy of a combinatorial immunotherapy with DB, given as a long-term treatment, and the double immune checkpoint blockade of TIGIT and PD-L1 was shown using a resistant murine model of NB, followed by an analysis of the tumor tissue. We detected both TIGIT ligands, CD112 and CD155, on all NB cell lines analyzed. Although ADCC by DB resulted in a strong activation of NK cells leading to an effective tumor cell lysis, a remarkable induction of PD-L1 expression on NB cells, and of TIGIT and PD-1 on effector cells, especially on NK cells, was observed. Additional anti-TIGIT or anti-PD-L1 treatments effectively inhibited tumor growth and improved survival of the mice treated with DB. The superior antitumor effects were observed in the "DB + double immune checkpoint blockade" group, showing an almost complete eradication of the tumors and the highest OS, even under resistant conditions. An analysis of tumor tissue revealed both TIGIT and TIGIT ligand expression on myeloid-derived suppressor cells (MDSCs), suggesting additional mechanisms of protumoral effects in NB. Our data show that the targeting of TIGIT and PD-L1 significantly improves the antitumor efficacy of anti-GD2 immunotherapy, with DB presenting a new effective combinatorial treatment strategy against high-risk tumors.

Chemotherapeutics Used for High-Risk Neuroblastoma Therapy Improve the Efficacy of Anti-GD2 Antibody Dinutuximab Beta in Preclinical Spheroid Models

Anti-disialoganglioside GD2 antibody ch14.18/CHO (dinutuximab beta, DB) improved the outcome of patients with high-risk neuroblastoma (HR-NB) in the maintenance phase. We investigated chemotherapeutic compounds used in newly diagnosed patients in combination with DB. Vincristine, etoposide, carboplatin, cisplatin, and cyclophosphamide, as well as DB, were used at concentrations achieved in pediatric clinical trials. The effects on stress ligand and checkpoint expression by neuroblastoma cells and on activation receptors of NK cells were determined by using flow cytometry. NK-cell activity was measured with a CD107a/IFN-γ assay. Long-term cytotoxicity was analyzed in three spheroid models derived from GD2-positive neuroblastoma cell lines (LAN-1, CHLA 20, and CHLA 136) expressing a fluorescent near-infrared protein. Chemotherapeutics combined with DB in the presence of immune cells improved cytotoxic efficacy up to 17-fold compared to in the controls, and the effect was GD2-specific. The activating stress and inhibitory checkpoint ligands on neuroblastoma cells were upregulated by the chemotherapeutics up to 9- and 5-fold, respectively, and activation receptors on NK cells were not affected. The CD107a/IFN-γ assay revealed no additional activation of NK cells by the chemotherapeutics. The synergistic effect of DB with chemotherapeutics seems primarily attributed to the combined toxicity of antibody-dependent cellular cytotoxicity and chemotherapy, which supports further clinical evaluation in frontline induction therapy.

BCL11B depletion induces the development of highly cytotoxic innate T cells out of IL-15 stimulated peripheral blood αβ CD8+ T cells

BCL11B, an essential transcription factor for thymopoiesis, regulates also vital processes in post-thymic lymphocytes. Increased expression of BCL11B was recently correlated with the maturation of NK cells, whereas reduced BCL11B levels were observed in native and induced T cell subsets displaying NK cell features. We show that BCL11B-depleted CD8+ T cells stimulated with IL-15 acquired remarkable innate characteristics. These induced innate CD8+ (iiT8) cells expressed multiple innate receptors like NKp30, CD161, and CD16 as well as factors regulating migration and tissue homing while maintaining their T cell phenotype. The iiT8 cells effectively killed leukemic cells spontaneously and neuroblastoma spheroids in the presence of a tumor-specific monoclonal antibody mediated by CD16 receptor activation. These iiT8 cells integrate the innate natural killer cell activity with adaptive T cell longevity, promising an interesting therapeutic potential. Our study demonstrates that innate T cells, albeit of limited clinical applicability given their low frequency, can be efficiently generated from peripheral blood and applied for adoptive transfer, CAR therapy, or combined with therapeutic antibodies.

Immune Response and Outcome of High-Risk Neuroblastoma Patients Immunized with Anti-Idiotypic Antibody Ganglidiomab: Results from Compassionate-Use Treatments

(1) Background: High-risk neuroblastoma (HR-NB) is associated with a poor prognosis despite a multimodal high-intensity treatment regimen, including immunotherapy with anti-GD2 monoclonal antibodies (mAb). Here, we investigated the effects of an anti-idiotypic vaccine based on the mAb ganglidiomab that structurally mimics GD2. (2) Methods: Patients with HR-NB treated with anti-GD2 mAb dinutuximab beta and who achieved complete remission after frontline or salvage therapy were offered the vaccine (0.5 mg ganglidiomab adsorbed to Alhydrogel^®). Side effects (CTCAE v4.03) and immune responses were determined on each visit. We also evaluated the time to relapse or progression until the last follow-up. (3) Results: Seven HR-NB patients (five frontlines, two relapsed) received 6-22 subcutaneous injections every two weeks. Six of the seven patients showed an immune response. The non-responding patient had a haploidentical stem cell transplantation as part of the previous treatment. No fever, pain, neuropathy, or toxicities ≥ grade 3 occurred during or post-treatment. All immunized patients did not experience relapses or progressions of their neuroblastoma. (4) Conclusions: This is the first-in-man use of the ganglidiomab vaccine, which was well-tolerated, and all patients not pre-treated by haploidentical transplantation developed vaccine-specific immune responses. These findings provide an important basis for the design of prospective clinical trials.

Immunophenotyping of Circulating and Intratumoral Myeloid and T Cells in Glioblastoma Patients

Glioblastoma is the most common and lethal primary brain malignancy that almost inevitably recurs as therapy-refractory cancer. While the success of immune checkpoint blockade (ICB) revealed the immense potential of immune-targeted therapies in several types of cancers outside the central nervous system, it failed to show objective responses in glioblastoma patients as of now. The ability of glioblastoma cells to drive multiple modes of T cell dysfunction while exhibiting low-quality neoepitopes, low-mutational load, and poor antigen priming limits anti-tumor immunity and efficacy of antigen-unspecific immunotherapies such as ICB. An in-depth understanding of the GBM immune landscape is essential to delineate and reprogram such immunosuppressive circuits during disease progression. In this view, the present study aimed to characterize the peripheral and intratumoral immune compartments of 35 glioblastoma patients compared to age- and sex-matched healthy control probands, particularly focusing on exhaustion signatures on myeloid and T cell subsets. Compared to healthy control participants, different immune signatures were already found in the peripheral circulation, partially related to the steroid medication the patients received. Intratumoral CD4+ and CD8+ TEM cells (CD62L^low/CD45RO^high) revealed a high expression of PD1, which was also increased on intratumoral, pro-tumorigenic macrophages/microglia. Histopathological analysis further identified high PSGL-1 expression levels of the latter, which has recently been linked to increased metastasis in melanoma and colon cancer via P-selectin-mediated platelet activation. Overall, the present study comprises immunophenotyping of a patient cohort to give implications for eligible immunotherapeutic targets in neurooncology in the future.

The Immunocytokine FAP-IL-2v Enhances Anti-Neuroblastoma Efficacy of the Anti-GD2 Antibody Dinutuximab Beta

Simple Summary

Since IL-2 co-treatment did not show any therapeutic benefit in the GD₂-directed treatment of high-risk neuroblastoma (NB) but strongly induced regulatory T cells (Treg), we investigated here the immunocytokine FAP-IL-2v stimulating NK and cytotoxic T cells without induction of Treg. We first detected FAP on NB- and myeloid-derived suppressor cells (MDCS) in tumor tissue and showed a tumor-cell-dependent enhancement in FAP expression by fibroblasts. Treatment of leukocytes with FAP-IL-2v increased ADCC mediated by the anti-GD₂ antibody dinutuximab beta (DB) against NB cells. We next evaluated the antitumor efficacy of a combinatorial immunotherapy by applying DB and FAP-IL-2v and observed strongly reduced tumor growth and improved survival in experimental mice. Analysis of tumor tissue revealed increased NK and cytotoxic T cell numbers and reduced Treg compared to controls. Our data show that FAP-IL-2v is a potent immunocytokine that augments the efficacy of DB against NB, providing a promising alternative to IL-2.

Abstract

Treatment of high-risk neuroblastoma (NB) patients with the anti-GD₂ antibody (Ab) dinutuximab beta (DB) improves survival by 15%. Ab-dependent cellular cytotoxicity (ADCC) is the major mechanism of action and is primarily mediated by NK cells. Since IL-2 co-treatment did not show a therapeutic benefit but strongly induced Treg, we investigated here a DB-based immunotherapy combined with the immunocytokine FAP-IL-2v, which comprises a fibroblast activation protein α (FAP)-specific Ab linked to a mutated IL-2 variant (IL-2v) with abolished binding to the high-affinity IL-2 receptor, thus stimulating NK cells without induction of Treg. Effects of FAP-IL-2v on NK cells, Treg and ADCC mediated by DB, as well as FAP expression in NB, were investigated by flow cytometry, calcein-AM-based cytotoxicity assay and RT-PCR analysis. Moreover, the impact of soluble factors released from tumor cells on FAP expression by primary fibroblasts was assessed. Finally, a combined immunotherapy with DB and FAP-IL-2v was evaluated using a resistant syngeneic murine NB model. Incubation of leukocytes with FAP-IL-2v enhanced DB-specific ADCC without induction of Treg. FAP expression on NB cells and myeloid-derived suppressor cells (MDCS) in tumor tissue was identified. A tumor-cell-dependent enhancement in FAP expression by primary fibroblasts was demonstrated. Combination with DB and FAP-IL-2v resulted in reduced tumor growth and improved survival. Analysis of tumor tissue revealed increased NK and cytotoxic T cell numbers and reduced Treg compared to controls. Our data show that FAP-IL-2v is a potent immunocytokine that augments the efficacy of DB against NB, providing a promising alternative to IL-2.

First-line Anti-GD2 Therapy Combined With Consolidation Chemotherapy in 3 Patients With Newly Diagnosed Metastatic Ewing Sarcoma or Ewing-like Sarcoma

Despite multimodal therapy, the prognosis of patients with metastatic Ewing sarcoma (ES) remains poor, with new treatments urgently needed. The disialoganglioside GD2, a well-established tumor-associated antigen, is expressed in 40% to 90% of ES cells, making it a suitable therapeutic target. Here we report 3 cases with newly diagnosed, metastatic, GD2-positive ES or Ewing-like sarcoma treated with the anti-GD2 antibody dinutuximab beta in addition to standard chemotherapeutic regimens. Treatment was well-tolerated, and all patients achieved complete remission, without evidence of relapse. First-line anti-GD2 immunotherapy in patients with metastatic, GD2-positive ES or Ewing-like sarcoma represents a promising therapeutic option that warrants further clinical evaluation.

GMP-Compliant Manufacturing of TRUCKs: CAR T Cells targeting GD2 and Releasing Inducible IL-18

Chimeric antigen receptor (CAR)-engineered T cells can be highly effective in the treatment of hematological malignancies, but mostly fail in the treatment of solid tumors. Thus, approaches using 4^th advanced CAR T cells secreting immunomodulatory cytokines upon CAR signaling, known as TRUCKs (“T cells redirected for universal cytokine-mediated killing”), are currently under investigation. Based on our previous development and validation of automated and closed processing for GMP-compliant manufacturing of CAR T cells, we here present the proof of feasibility for translation of this method to TRUCKs. We generated IL-18-secreting TRUCKs targeting the tumor antigen GD₂ using the CliniMACS Prodigy^® system using a recently described “all-in-one” lentiviral vector combining constitutive anti-GD₂ CAR expression and inducible IL-18. Starting with 0.84 x 10⁸ and 0.91 x 10⁸ T cells after enrichment of CD4⁺ and CD8⁺ we reached 68.3-fold and 71.4-fold T cell expansion rates, respectively, in two independent runs. Transduction efficiencies of 77.7% and 55.1% was obtained, and yields of 4.5 x 10⁹ and 3.6 x 10⁹ engineered T cells from the two donors, respectively, within 12 days. Preclinical characterization demonstrated antigen-specific GD₂-CAR mediated activation after co-cultivation with GD₂-expressing target cells. The functional capacities of the clinical-scale manufactured TRUCKs were similar to TRUCKs generated in laboratory-scale and were not impeded by cryopreservation. IL-18 TRUCKs were activated in an antigen-specific manner by co-cultivation with GD₂-expressing target cells indicated by an increased expression of activation markers (e.g. CD25, CD69) on both CD4⁺ and CD8⁺ T cells and an enhanced release of pro-inflammatory cytokines and cytolytic mediators (e.g. IL-2, granzyme B, IFN-γ, perforin, TNF-α). Manufactured TRUCKs showed a specific cytotoxicity towards GD₂-expressing target cells indicated by lactate dehydrogenase (LDH) release, a decrease of target cell numbers, microscopic detection of cytotoxic clusters and detachment of target cells in real-time impedance measurements (xCELLigence). Following antigen-specific CAR activation of TRUCKs, CAR-triggered release IL-18 was induced, and the cytokine was biologically active, as demonstrated in migration assays revealing specific attraction of monocytes and NK cells by supernatants of TRUCKs co-cultured with GD₂-expressing target cells. In conclusion, GMP-compliant manufacturing of TRUCKs is feasible and delivers high quality T cell products.

Comparison of three different methods to detect bone marrow involvement in patients with neuroblastoma

Purpose

Neuroblastoma (NB) is the most frequent extracranial tumor in children. The detection of bone marrow (BM) involvement is crucial for correct staging and risk-adapted treatment. We compared three methods regarding the detection of NB involvement in BM.

Methods

Eighty-one patients with NB were included in this retrospective study. BM samples were obtained at designated time points at study entry and during treatment or follow-up. The diagnostic tools for BM analysis included cytomorphology (CM), flow cytometry (FCM) and automatic immunofluorescence plus fluorescence in situ hybridization (AIPF).

Results

We analyzed 369 aspirates in 81 patients in whom AIPF, CM, and FCM were simultaneously available. During the observation period, NB cells were detected in 86/369 (23.3%) cases, by CM in 32/369 (8.7%), by FCM in 52 (14.1%), and by AIPF in 72 (19.5%) samples. AIPF and/or FCM confirmed all positive results obtained in CM and detected 11 additional positive BM aspirates in 294 CM negative samples (p < 0,001). Survival of patients with BM involvement at study entry identified solely by FCM/AIPF was 17.4% versus 0% for patients in whom BM involvement was already identified by CM.

Conclusion

The combination of AIPF/FCM yielded the highest detection rate of NB cells in BM. AIPF was the single, most sensitive method in detecting these cells. Although CM did not provide any additional positive results, it is still a useful, readily available and cost-effective tool. The prognostic significance of FCM and AIPF should be confirmed in a prospective study with a larger number of patients.

Immunomonitoring of Stage IV Relapsed Neuroblastoma Patients Undergoing Haploidentical Hematopoietic Stem Cell Transplantation and Subsequent GD2 (ch14.18/CHO) Antibody Treatment

Haploidentical stem cell transplantation (haplo SCT) in Stage IV neuroblastoma relapsed patients has been proven efficacious, while immunotherapy utilizing the anti-GD2 antibody dinutuximab beta has become a standard treatment for neuroblastoma. The combinatorial therapy of haplo SCT and dinutuximab may potentiate the efficacy of the immunotherapy. To gain further understanding of the synergistic effects, functional immunomonitoring was assessed during the clinical trial CH14.18 1021 Antibody and IL2 After haplo SCT in Children with Relapsed Neuroblastoma (NCT02258815). Rapid immune reconstitution of the lymphoid compartment was confirmed, with clinically relevant dinutuximab serum levels found in all patients over the course of treatment. Only one patient developed human anti-chimeric antibodies (HACAs). In-patient monitoring revealed highly functional NK cell posttransplant capable of antibody-dependent cellular cytotoxicity (ADCC). Degranulation of NK cell subsets revealed a significant response increased by dinutuximab. This was irrespective of the KIR receptor–ligand constellation within the NK subsets, defined by the major KIR receptors CD158a, CD158b, and CD158e. Moreover, complement-dependent cytotoxicity (CDC) was shown to be an extremely potent effector-cell independent mechanism of tumor cell lysis, with a clear positive correlation to GD2 expression on the cancer cells as well as to the dinutuximab concentrations. The ex vivo testing of patient-derived effector cells and the sera collected during dinutuximab therapy demonstrated both high functionality of the newly established lymphoid immune compartment and provided confidence that the antibody dosing regimen was sufficient over the duration of the dinutuximab therapy (up to nine cycles in a 9-month period). During the course of the dinutuximab therapy, proinflammatory cytokines and markers (sIL2R, TNFa, IL6, and C reactive protein) were significantly elevated indicating a strong anti-GD2 immune response. No impact of FcGR polymorphism on event-free and overall survival was found. Collectively, this study has shown that in-patient functional immunomonitoring is feasible and valuable in contributing to the understanding of anti-cancer combinatorial treatments such as haplo SCT and antibody immunotherapy.

Inebilizumab in AQP4-Ab-positive neuromyelitis optica spectrum disorder

Until recently, the use of preventative immunotherapy in neuromyelitis optica spectrum disorders (NMOSD) was based on observational studies and clinical experiences. Meanwhile, the first drugs, among others the monoclonal antibody inebilizumab, were approved for the treatment of aquaporin-4 (AQP4) antibody-positive NMOSD. Inebilizumab binds to the CD19 antigen on B cells and leads to B-cell depletion. The first two dosages of 300 mg inebilizumab are administered intravenously at an interval of 2 weeks followed by further infusions every 6 months. In the placebo-controlled pivotal phase II/III study N-MOmentum, inebilizumab significantly prolonged the time to a first adjudicated relapse in AQP4 antibody-positive patients compared with placebo. The most frequent side effects were infusion reactions, urinary and respiratory tract infections, and arthralgia. This review presents data on clinical and preclinical pharmacology, administration, safety aspects and clinical trials of inebilizumab.

Nivolumab and dinutuximab beta in two patients with refractory neuroblastoma

BACKGROUND

Neuroblastoma (NB) is the most frequent extracranial solid tumor in children. More than 50% of patients present with widespread (stage M) or refractory disease. In these patients, event-free and overall survival was improved by the addition of the anti-disialoganglioside antibody dinutuximab beta (DB) following multimodal conventional therapy. However, the prognosis of patients with refractory/relapsed NB remains poor. In the past decade, immunotherapy approaches with checkpoint inhibitors were approved for patients with certain malignant diseases such as melanoma or Hodgkin lymphoma. In preclinical models, DB resulted in an upregulation of the programmed cell death protein 1 (PD-1) checkpoint in NB cell lines and a combined treatment of DB with a murine anti-PD-1 checkpoint inhibitor showed a synergistic effect in a NB mouse model.

CASE PRESENTATIONS

Two patients were admitted with refractory metastatic NB. In the 4-year-old girl, NB was diagnosed in 2013. She completed her first-line therapy with a first remission in 2015, but suffered a relapse in 2017. Treatment with chemotherapy and DB resulted in progressive disease after transient improvement. In the 17-year-old young man, NB was first diagnosed in April 2010. After two local relapses in 2011 and 2014, a metastatic relapse and a large abdominal tumor bulk were found in 2018. Despite transient improvement with multimodal therapy, progressive metastatic disease was observed in May 2019. Both patients had a satisfactory quality of life. Therefore, treatment with DB and nivolumab was performed-in the girl from October 2018 until August 2019, in the young man since June 2019. Tolerance to treatment was excellent. The girl continues to be in complete remission 6 months after therapy was stopped. In the young man, the soft tissue lesions disappeared completely, the skeletal lesions regressed substantially after 9 months of his still ongoing treatment.

CONCLUSIONS

The combination of DB with the checkpoint inhibitor nivolumab led to complete and a very good partial remission in two patients with relapsed/refractory NB. Prospective trials are warranted to clarify the role of this novel approach in a larger number of patients.

Reduction of CD11b+ myeloid suppressive cells augments anti-neuroblastoma immune response induced by the anti-GD2 antibody ch14.18/CHO

Neuroblastoma (NB) still remains a major challenge in pediatric oncology. We recently showed CD11b⁺-dependent upregulation of the PD-1/PD-L1 checkpoint on NB cells treated with the chimeric anti-GD₂ antibody (Ab) ch14.18/CHO. Here, we report effects of reduction of CD11b⁺ myeloid suppressive cells on ch14.18/CHO immunotherapy against NB. Flow cytometry, immunohistochemistry and RT-PCR were used to assess tumor infiltrating leukocytes and expression of myeloid suppressive cell-associated genes. XTT assay was used to show impact of 5-FU on tumor and effector cells. Antitumor effects of the combined treatment with ch14.18/CHO and reduction of myeloid suppressive cells were evaluated in a syngeneic NB mouse model. Tumor tissue of untreated mice showed a strong infiltration by CD11b⁺ cells (53% of all tumor infiltrating leukocytes). RT-PCR analysis of tumors revealed strong expression of the myeloid suppressive cell-associated genes analyzed with the strongest induction of M-CSFr, CCL2, IL-1β, IL-4, IL-6 r, IL-8, Arg1, and NOS2. Compared to controls, application of anti-CD11b Ab resulted in reduction of both CD11b⁺ cells in tumors and expression of myeloid suppressive cell-associated genes as well as delayed tumor growth and prolonged survival. These effects could be further improved by 5-FU. Importantly, the combinatorial immunotherapy with ch14.18/CHO and 5-FU showed the strongest antitumor effects and superior survival rates. In conclusion, reduction of immune suppressive myeloid cells augments anti-NB efficacy of a ch14.18/CHO-based immunotherapy representing a new effective treatment strategy against GD₂-positive cancers.

Impact of IL-2 on Treatment Tolerance in Patients With High-Risk Neuroblastoma Treated With Dinutuximab Beta-Based Immunotherapy

Patients with high-risk neuroblastoma treated with continuous long-term infusion of anti-GD2 antibody dinutuximab beta (DB) in combination with IL-2 show an acceptable safety profile. Here, we compared treatment tolerance with and without IL-2. Ninety-nine patients with high-risk neuroblastoma received up to five cycles of DB given as long-term infusion (10 mg/m²/d, 100 mg/m²; per cycle) with IL-2 (53 patients; regimen A; 6 × 10⁶ IU/m²/d; 60 × 10⁶ IU/m²/cycle) and without IL-2 (46 patients; regimen B) in a single-center compassionate use program. Clinical parameters (body temperature, vital signs, Lansky performance score), laboratory values [C-reactive protein, IFN-γ, IL-6, and IL-18 (cycle 1)], and requirement of i.v. co-medication (e.g., morphine, metamizole) were systematically assessed. Patients with stable clinical parameters and that did not require co-medication were defined as potential "outpatient candidates." Patients showed higher levels of body temperature and CRP in regimen A compared to B. However, IL-6 serum concentrations were similar in pts of both cohorts in the first cycle. Patients receiving regimen B showed a shorter time to achieve normal vital parameters and required less co-medication compared to patients in regimen A that resulted in a shorter median time period to discharge and to achieve a potential outpatient status (6d regimen A and 3-5d regimen B after start of antibody infusion, respectively). This study shows that omitting IL-2 from immunotherapy with DB allows reduced co-medication and hospitalization time and therefore results in improved quality of life in patients with high-risk neuroblastoma.

Neuroblastoma with intracerebral metastases and the need for neurosurgery: a single-center experience

OBJECTIVE

Intracerebral metastases in neuroblastoma patients are rare, and information about the indication for and the outcome of neurosurgical procedures in this setting is scarce in the literature. The authors' aim in the present study was to report a single-center experience with the neurosurgical treatment of intracerebral metastases in neuroblastoma.

METHODS

This study is a retrospective single-center analysis of all neurosurgical strategies used in the treatment of intracerebral metastases in neuroblastoma patients.

RESULTS

Between 2009 and 2017, 237 pediatric patients (94 girls, 143 boys) with a mean age of 39 months at diagnosis were treated for neuroblastoma. Five (2.1%) of the 237 patients had a neurosurgical procedure for intracerebral metastases. The metastases occurred a mean of 46 months after initial diagnosis. All of these patients had neuroblastoma stage 4. Indications for surgery were recurrent metastases after initial successful oncological treatment or progression of the metastasis under oncological treatment as well as deterioration of neurological function. Intraoperatively, the tumor usually had a distinguishable dissection plane but was infiltrative to adjacent nerves in some spots. Mean overall survival after the neurosurgical procedure was 22 months. Furthermore, in another 3 patients, a neurosurgical procedure was done for an intracranial but extracerebral metastasis.

CONCLUSIONS

Neurosurgical procedures for intracerebral metastases in neuroblastoma patients are rare and were performed in 2.1% of patients in the present study. Intracerebral metastases occurred during disease progression, and the prognosis after surgery was very limited. The main indications for surgery were rapid neurological deterioration or recurrence of the metastasis after initial successful oncological treatment. Intraoperatively, the metastases usually had a distinguishable dissection plane from the normal brain tissue.

Low CD4⁺/CD25⁺/CD127⁻ regulatory T cell- and high INF-γ levels are associated with improved survival of neuroblastoma patients treated with long-term infusion of ch14.18/CHO combined with interleukin-2

Immunotherapy with the anti-GD₂ antibody (Ab) ch14.18/CHO in combination with interleukin 2 (IL-2) has improved survival of high-risk neuroblastoma (NB) patients. Here, we report immunotherapy-related effects on circulating NK cells, regulatory T cells (T_regs), granulocytes as well as on Ab-dependent cell-mediated cytotoxicity (ADCC) and cytokines IFN-γ, IL-6, IL-10, IL-18 and CCL2 and their association with progression-free survival (PFS).

In a closed single-center program, 53 patients received five cycles of 6 × 10⁶ IU/m² subcutaneous IL-2 (d1-5; 8–12) combined with long-term infusion (LTI) of 100 mg/m² ch14.18/CHO (d8-18). Immune cells and cytokines were analyzed by flow cytometry and ADCC by calcein-AM-based cytotoxicity assay.

IL-2 administration increased cytotoxic NK cell-, eosinophil- and T_reg counts in cycle 1 (2.9-, 3.1- and 20.7-fold, respectively) followed by further increase in subsequent cycles, whereas neutrophil levels were elevated only after the ch14.18/CHO infusion (2.4-fold change). Serum concentrations of IFN-γ, IL-6, IL-10, IL-18 and CCL2 in cycle 1 were increased during the combinatorial therapy (peak levels of 3,656 ± 655 pg/ml, 162 ± 38 pg/ml, 20.91 ± 4.74 pg/ml, 1,584 ± 196 pg/ml and 2,159 ± 252 pg/ml, respectively). Surprisingly, we did not observe any correlation between NK-, eosinophil- or neutrophil levels and PFS. In contrast, patients with low T_regs showed significantly improved PFS compared to those who had high levels. T_reg counts negatively correlated with INF-γ serum concentrations and patients with high INF-γ and IL-18 had significantly improved survival compared to those with low levels.

In conclusion, LTI of ch14.18/CHO in combination with IL-2 resulted in T_reg induction that inversely correlated with IFN-γ levels and PFS.

Management of tumor rupture and abdominal compartment syndrome in an infant with bilateral high risk stage 4 neuroblastoma: A case report

RATIONALE

Tumor rupture and bleeding at initial presentation of infants with neuroblastoma (NBL) is a rare, but life threatening condition and challenge in pediatric oncology. Here, we report successful multidisciplinary management of an abdominal compartment syndrome as a result of tumor rupture and bleeding in an infant with bilateral high risk stage 4 NBL.

PATIENT CONCERNS

The patient was admitted to a cooperating hospital with vomiting, failure to thrive and a large mass in the abdomen and was then referred to our center.

DIAGNOSES

Stage 4 NBL with MYC-N amplification and 1p36 deletion was diagnosed in an 11 months old girl. Due to rapid and massive tumor growth she developed abdominal compression with renal failure, severe bleeding, and tumor lysis syndrome (TLS).

INTERVENTIONS

Surgical decompression by enterostomy, local, and systemic bleeding control with platelets and coagulation factors, antiinfective and TLS therapy were effective in stabilizing the patient's condition. This allowed initiation of the multimodal antineoplastic treatment according to protocol NB 2004.

OUTCOMES

Mechanical ventilation was stopped after 11 days, the abdominal wall was closed 3 months after the start of therapy, and treatment according to the protocol be started and successfully completed.

LESSONS

Only the immediate, coordinated multidisciplinary intervention managed to overcome the life-threatening abdominal compartment syndrome and its associated problems, eventually enabling successful curative treatment.

Randomized use of anti-GD2 antibody dinutuximab beta (DB) long-term infusion with and without subcutaneous interleukin-2 (scIL-2) in high-risk neuroblastoma patients with relapsed and refractory disease: Results from the SIOPEN LTI-trial

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Background: We determined the role of scIL-2 combined with long term infusion (LTI) of DB in patients (pts) with high-risk relapsed/refractory neuroblastoma. Methods: 160 pts were enrolled into an open label SIOPEN Phase II clinical trial (EudraCT 2009-018077-31). Pts were randomly assigned to receive up to 5 cycles of 100 mg/m2 DB-LTI (d8-17) and 160 mg/m2 oral isotretinoin (d19-32) (81 pts) with and without 6x106IU/m2 scIL-2 (d1-5; 8-12) (79 pts). Endpoints were toxicity, response rates and 2yrs-event free and -overall survival. Results: Between 07/2014 and 07/2017, 160 pts from 11 countries were randomised. Median follow-up is 2.6 years. Pts were well balanced between arms according to stage, age, MYCN amplification, patients with relapse and remission status. The 2yrs-EFS and -OS for DB (81 pts) vs. DB combined with scIL-2 (79 pts) was 59%±6% vs 65%±6% (p = 0.721) and 79%±5% vs 84%±4% (p = 0.904). In 97 pts with evaluable disease, a response rate of 49% (9% CR, 40% PR) vs 52% (26% CR, 26% PR) after treatment with DB vs DB and scIL-2 was observed. Grade 3&4 fever (16% vs 46%, P = 0.000), allergic reaction (1% vs 14%, P = 0.004), hematological toxicity (46% vs 66%, P = 0.013) and neurotoxicity (0% vs 8%, p = 0.003) were significantly worse in the combination arm, but no difference was seen for capillary leak, gastrointestinal, liver enzyme elevation and pain. Paraplegia possibly related to the treatment was observed in 2 pts in the combination arm, none in the arm without scIL-2, and one resolved to baseline. A subgroup of 34 pts who had a relapse and measurable disease at treatment start, showed a 2yrs-EFS and -OS in DB (17 pts) vs DB combined with scIL-2 (17 pts) of 35%±12% vs 69%±12% (p = 0.116) and 59%±12% vs 81%±10% (p = 0.167). However, this trend was statistically not significant. Pharmacokinetic and HACA response between both arms was not different with overlapping antibody concentration-time curves and a HACA response of 15/81 (19%) (DB) vs 16/79 (20%) (DB and scIL-2). Conclusions: No significant difference in efficacy of DB combined with scIL-2 and increased toxicity in this arm suggests that this schedule of scIL-2 is of no additional benefit. Clinical trial information: 2009-018077-31.

EZH2 Inhibition in Ewing Sarcoma Upregulates GD2 Expression for Targeting with Gene-Modified T Cells

Chimeric antigen receptor (CAR) engineering of T cells allows one to specifically target tumor cells via cell surface antigens. A candidate target in Ewing sarcoma is the ganglioside G_D2, but heterogeneic expression limits its value. Here we report that pharmacological inhibition of Enhancer of Zeste Homolog 2 (EZH2) at doses reducing H3K27 trimethylation, but not cell viability, selectively and reversibly induces G_D2 surface expression in Ewing sarcoma cells. EZH2 in Ewing sarcoma cells directly binds to the promoter regions of genes encoding for two key enzymes of G_D2 biosynthesis, and EZH2 inhibition enhances expression of these genes. G_D2 surface expression in Ewing sarcoma cells is not associated with distinct in vitro proliferation, colony formation, chemosensitivity, or in vivo tumorigenicity. Moreover, disruption of G_D2 synthesis by gene editing does not affect its in vitro behavior. EZH2 inhibitor treatment sensitizes Ewing sarcoma cells to effective cytolysis by G_D2-specific CAR gene-modified T cells. In conclusion, we report a clinically applicable pharmacological approach for enhancing efficacy of adoptively transferred G_D2-redirected T cells against Ewing sarcoma, by enabling recognition of tumor cells with low or negative target expression.

Co-expression of IL-15 enhances anti-neuroblastoma effectivity of a tyrosine hydroxylase-directed DNA vaccination in mice

Long-term survival of high-risk neuroblastoma (NB) patients still remains under 50%. Here, we report the generation, in vitro characterization and anti-tumor effectivity of a new bicistronic xenogenic DNA vaccine encoding tyrosine hydroxylase (TH) that is highly expressed in NB tumors, and the immune stimulating cytokine interleukin 15 (IL-15) that induces cytotoxic but not regulatory T cells. The DNA sequences of TH linked to ubiquitin and of IL-15 were integrated into the bicistronic expression vector pIRES. Successful production and bioactivity of the vaccine-derived IL-15- and TH protein were shown by ELISA, bioactivity assay and western blot analysis. Further, DNA vaccine-driven gene transfer to the antigen presenting cells of Peyer’s patches using attenuated Salmonella typhimurium that served as oral delivery system was shown by immunofluorescence analysis. The anti-tumor effect of the generated vaccine was evaluated in a syngeneic mouse model (A/J mice, n = 12) after immunization with S. typhimurium (3× prior and 3× after tumor implantation). Importantly, TH-/IL-15-based DNA vaccination resulted in an enhanced tumor remission in 45.5% of mice compared to controls (TH (16.7%), IL-15 (0%)) and reduced spontaneous metastasis (30.0%) compared to controls (TH (63.6%), IL-15 (70.0%)). Interestingly, similar levels of tumor infiltrating CD8⁺ T cells were observed among all experimental groups. Finally, co-expression of IL-15 did not result in elevated regulatory T cell levels in tumor environment measured by flow cytometry. In conclusion, co-expression of the stimulatory cytokine IL-15 enhanced the NB-specific anti-tumor effectivity of a TH-directed vaccination in mice and may provide a novel immunological approach for NB patients.

Impact of HACA on Immunomodulation and Treatment Toxicity Following ch14.18/CHO Long-Term Infusion with Interleukin-2: Results from a SIOPEN Phase 2 Trial

GD₂-directed immunotherapies improve survival of high-risk neuroblastoma (NB) patients (pts). Treatment with chimeric anti-GD₂ antibodies (Ab), such as ch14.18, can induce development of human anti-chimeric Ab (HACA). Here, we report HACA effects on ch14.18/CHO pharmacokinetics, pharmacodynamics and pain intensity in pts treated by long-term infusion (LTI) of ch14.18/CHO combined with IL-2. 124 pts received up to 5 cycles of ch14.18/CHO 10 days (d) infusion (10 mg/m²/d; d8–18) combined with s.c. IL-2 (6 × 10⁶ IU/m²/d; d1–5, d8–12). HACA, treatment toxicity, ch14.18/CHO levels, Ab-dependent cellular- (ADCC) and complement-dependent cytotoxicity (CDC) were assessed using respective validated assays. HACA-negative pts showed a steadily decreased pain in cycle 1 (74% pts without morphine by d5 of LTI) with further decrease in subsequent cycles. Ch14.18/CHO peak concentrations of 11.26 ± 0.50 µg/mL found in cycle 1 were further elevated in subsequent cycles and resulted in robust GD₂-specific CDC and ADCC. Development of HACA (21% of pts) resulted in strong reduction of ch14.18/CHO levels, abrogated CDC and ADCC. Surprisingly, no difference in pain toxicity between HACA-positive and -negative pts was found. In conclusion, ch14.18/CHO LTI combined with IL-2 results in strong activation of Ab effector functions. Importantly, HACA response abrogated CDC but did not affect pain intensity indicating CDC-independent pain induction.

Inflammatory response and treatment tolerance of long-term infusion of the anti-GD2 antibody ch14.18/CHO in combination with interleukin-2 in patients with high-risk neuroblastoma

BACKGROUND

The monoclonal anti-GD₂ antibody ch14.18/CHO in combination with IL-2 is active and effective in high-risk neuroblastoma (NB) patients. Here, we investigated the inflammatory response and treatment tolerance of long-term infusion (LTI) of ch14.18/CHO (10 × 10 mg/m² ; 24 hr) in combination with subcutaneous (s.c.) IL-2 in a single center program.

METHODS

Fifty-three NB patients received up to six cycles of 100 mg/m² ch14.18/CHO (d8-18, where d represents day(s)) as LTI combined with 6 × 10⁶ IU/m² s.c. IL-2 (d1-5; 8-12) and 160 mg/m² oral 13-cis retinoic acid (RA) (d19-32). Side effects of ch14.18/CHO and IL-2 treatment require hospitalization of patients on d8. Treatment tolerance was evaluated daily with clinical parameters (body temperature, vital signs, Lansky performance status, requirement of i.v. concomitant medication) to define an outpatient candidate status. sIL-2-R and C-reactive protein values were determined to assess the inflammatory response.

RESULTS

LTI of ch14.18/CHO (d8-18) in combination with s.c.IL-2 (d8-12) showed an acceptable treatment tolerance that allowed all patients to receive part of the treatment as an outpatient (median time point of discharge: d15 for all cycles). The treatment tolerance improved from cycle to cycle and the time to become an outpatient candidate decreased from d15 to d13 in subsequent cycles. Clinical and laboratory parameters indicate a maximum inflammatory response at d11 of each cycle. Interestingly, the soluble IL-2 receptor remained increased at baseline of the next cycle indicating immune activation over the entire treatment period of 6 months.

CONCLUSIONS

LTI of ch14.18/CHO combined with s.c.IL-2 shows an improved tolerance in subsequent cycles allowing outpatient treatment.

Tolerability, response and outcome of high-risk neuroblastoma patients treated with long-term infusion of anti-GD2 antibody ch14.18/CHO

Immunotherapy with short term infusion (STI) of monoclonal anti-GD₂ antibody (mAb) ch14.18 (4 × 25 mg/m²/d; 8-20 h) in combination with cytokines and 13-cis retinoic acid (RA) prolonged survival in high-risk neuroblastoma (NB) patients. Here, we investigated long-term infusion (LTI) of ch14.18 produced in Chinese hamster ovary cells (ch14.18/CHO; 10 × 10 mg/m²; 24 h) in combination with subcutaneous (s.c.) interleukin-2 (IL-2) in a single center program and report clinical response, toxicity and survival. Fifty-three high-risk NB patients received up to 6 cycles of 100 mg/m² ch14.18/CHO (d8-17) as LTI combined with 6 × 10⁶ IU/m² s.c. IL-2 (d1-5; 8-12) and 160 mg/m² oral RA (d19-32). Pain toxicity was documented with validated pain scores and intravenous (i.v.) morphine usage. Response was assessed in 37/53 evaluable patients following International Neuroblastoma Risk Group criteria. Progression-free (PFS) and overall survival (OS) was analyzed by the Kaplan-Meier method and compared to a matched historical control group from the database of AIEOP, the "Italian Pediatric Ematology and Oncology Association". LTI of ch14.18/CHO showed acceptable toxicity profile indicated by low pain scores, reduced i.v. morphine usage and low frequency of Grade ≥3 adverse events that allowed outpatient treatment. We observed a best response rate of 40.5% (15/37; 5 CR, 10 PR), 4-year (4 y) PFS of 33.1% (observation 0.1- 4.9 y, mean: 2.2 y) and a 4 y OS of 47.7% (observation 0.27 - 5.20 y, mean: 3.6 y). Survival of the entire cohort (53/53) and the relapsed patients (29/53) was significantly improved compared to historical controls. LTI of ch14.18/CHO thus shows an acceptable toxicity profile, objective clinical responses and a strong signal of clinical efficacy in NB patients.

PD-1 blockade augments anti-neuroblastoma immune response induced by anti-GD2 antibody ch14.18/CHO

Immunotherapy with anti-GD₂ antibody (Ab) ch14.18/CHO is effective for treatment of high-risk neuroblastoma (NB) patients and is mainly based on GD₂-specific Ab-dependent cellular cytotoxicity (ADCC). Strategies to further enhance the efficacy are important and currently explored in prospective clinical trials randomizing ch14.18/CHO ± IL-2. Recently, expression of programmed death 1 (PD-1) inhibitory receptor by effector cells and its ligand (PD-L1) by tumor cells has been shown. Here, we report for the first time effects of PD-1 blockade on ch14.18/CHO-based immunotherapy and mechanisms involved. Expression of PD-1 and PD-L1 on NB and effector cells was analyzed by RT-PCR and flow cytometry in the presence of ch14.18/CHO and/or IL-2. The effect of PD-1 blockade on ch14.18/CHO-mediated anti-NB immune response was evaluated using anti-PD-1 Ab both in vitro (Nivolumab) and in a syngeneic PD-L1⁺/GD₂⁺ NB mouse model (anti-mouse PD-1). Culture of NB cells LA-N-1 (low PD-L1 baseline expression) with leukocytes and subtherapeutic ch14.18/CHO concentrations for 24 h induced strong upregulation of PD-L1, which was further increased by IL-2 resulting in complete inhibition of ch14.18/CHO-mediated ADCC. Importantly, blockade with Nivolumab reversed the PD-L1-dependent inhibition of ADCC. Similarly, co-incubation with anti-CD11b Ab abrogated the PD-L1 upregulation and restored ADCC. Mice treated with ch14.18/CHO in combination with PD-1 blockade showed a strong reduction of tumor growth, prolonged survival and the highest cytotoxicity against NB cells. In conclusion, ch14.18/CHO-mediated effects upregulate the inhibitory immune checkpoint PD-1/PD-L1, and combination of ch14.18/CHO with PD-1 blockade results in synergistic treatment effects in mice representing a new effective treatment strategy against GD₂-positive cancers.

Effect of PD1/PD-L1 checkpoint blockade on efficacy of anti-GD2 antibody ch14.18/CHO in neuroblastoma

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Background: Immunotherapy (IT) with anti-GD2 antibody (Ab) ch14.18/CHO is effective for treatment of high-risk neuroblastoma (NB) patients mainly due to induction of GD2-specific Ab-dependent cellular cytotoxicity (ADCC). Methods to further enhance the effect are important and currently explored in prospective clinical trials randomizing ch14.18/CHO ± scIL-2. Programmed death-1 (PD-1) is an inhibitory receptor expressed by activated T- and NK-cells, and cancer cells express PD-1 ligand. Here, we report for the first time effect and mechanism of PD-1/PD-L1 blockade in the context of ch14.18/CHO-based IT in preclinical models. Methods: Expression of PD-L1 and PD-1 on NB cells and leukocytes was analyzed by RT-PCR and flow cytometry in the presence of ch14.18/CHO or IL-2. Mechanism of PD-L1 induction was analyzed with anti-CD11b Ab. The effect of PD-1/PD-L1 blockade on ch14.18/CHO-mediated anti-NB immune response was evaluated using anti-PD-1 Ab both in vitro (Nivolumab) and in the syngeneic GD2+ NB NXS2 mouse model (anti-mouse PD-1). Mice (n = 10) were treated with ch14.18/CHO (5x300 µg, i.p.) in combination with anti-PD-1 (8x250 µg, i.p.), and compared to controls. Results: Culture of LA-N-1 (low PD-L1 baseline expression) in the presence of leukocytes and subtherapeutic ch14.18/CHO concentrations for 24h induced strong upregulation of PD-L1 resulting in complete inhibition of ADCC mediated by ch14.18/CHO. Co-incubation with anti-CD11b Ab abrogated this PD-L1 upregulation. Importantly, blockade with Nivolumab reversed the PD-L1-dependent inhibition of ADCC. Mice treated with ch14.18/CHO in combination with PD-1 blockade showed a strong reduction of tumor growth and prolonged survival as well as the highest level of NB cell lysis mediated by serum and leukocytes compared to controls. Conclusions: Ch14.18/CHO-mediated effects upregulate the inhibitory checkpoint PD-1/PD-L1 and combination of ch14.18/CHO with PD-1/PD-L1 blockade results in synergistic treatment effects in mice. This concept will be evaluated in a clinical trial.

Survival of neuroblastoma patients treated by long-term infusion of anti-GD2 antibody ch14.18/CHO and killer-cell Ig-like receptor (KIR) genotypes and Fcγ-receptor polymorphisms

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Background: Receptors expressed on natural killer (NK) cells and their ligands on target cells involved in antibody-dependent cell-mediated cytotoxicity (ADCC) may influence outcome in patients (pts) with high-risk relapsed/refractory neuroblastoma (NB) treated by long-term infusion (LTI) of anti-GD2 antibody ch14.18/CHO Methods: 53 pts received 6x106 IU/m2 sc IL-2 (d1-5; 8-12), LTI of 100 mg/m2 ch14.18/CHO (d8-17) and 160 mg/m2 oral 13-cis-RA (d19-32) in a closed single center program (53 pts) (APN311-303). Polymorphisms in Fcγ-receptor genes 2A (H131R), -3A (V158F) and -3B (NA1/NA2), and KIR- as well as KIR ligand expression (HLA-C1; HLA-C2; HLA-Bw4+) were determined by real-time PCR. Results: The survival update of the APN311-303 cohort revealed a 5-y OS of 56.4±7.1% (mean OS 4.35y [0.3-6.2y]) and a 5-y PFS of 29.1±6.3% (mean PFS 2.4y [0.1 - 5.9y]). Median TTP/PFS was 1.35 y (95% CI: 0.21-2.48 y). This result is clearly superior to historical controls not treated with ch14.18/CHO with a 5-y OS of 14.8±6.8% (p < 0.005), indicating clinical efficacy of the treatment. In this cohort, we identified 26/53 pts with the NK- stimulatory KIR haplotype (2DS2+) who had superior OS- and PFS-rates compared to 18/53 pts with an inhibitory haplotype and KIR/KIR-ligand match (2DS2-, 3DL1+, Bw4+) (p < 0.02). Similarly, we found 33/53 pts with low affinity FCGR alleles (FCGR2A-H131R/R and/or FCGRA3A-V158 F/F). These patients showed lower PFS rates compared to 20/53 patients with high affinity FCGR polymorphisms (p < 0.01). ADCC analysis on day 15 of cycle 1 showed higher levels in the pt group with NK- stimulatory versus NK- inhibitory KIR/KIR ligand haplotypes (23±6 % vs. 6±2%, p < 0.01). A similar effect was observed in pts with high affinity FCGR polymorphisms with an ADCC increase of 20±6% compared to 11±2% in the low affinity FCGR control. Conclusions: KIR-haplotypes and FCGR- polymorphisms correlated with the functional immune parameter ADCC and clinical outcome, and thus support the relevance of ADCC for clinical efficacy of ch14.18/CHO in neuroblastoma.

Neuroblastoma patients with high-affinity FCGR2A, -3A and stimulatory KIR 2DS2 treated by long-term infusion of anti-GD2 antibody ch14.18/CHO show higher ADCC levels and improved event-free survival

Polymorphisms in Fc-gamma-receptor (FCGR) genes as well as killer cell immunoglobulin-like receptor (KIR) and KIR ligand (KIRL) repertoires may influence antitumor effects of monoclonal antibodies (mAb). Here, we systematically analyzed high- and low-affinity FCGR2A and -3A genotypes as well as stimulating and inhibitory KIR/KIRL combinations in 53 neuroblastoma (NB) patients treated by long-term infusion (LTI) of anti-GD₂ IgG1 Ab ch14.18/CHO using validated real-time PCR methods. Patients with high-affinity FCGR2A and -3A genotypes showed a higher level of Ab-dependent cell-mediated cytotoxicity (ADCC) on day 8 after the start of ch14.18/CHO and superior event-free survival (EFS) compared to patients with low FCGR genotypes. Similar observations were made for patients with stimulatory KIR/KIRL haplotype B (combination of KIR genes including activating receptor genes) compared to inhibitory haplotype A (a fixed set of genes encoding for inhibitory receptors, except 2DS4) and stronger effects were found in patients when haplotype B and high-affinity FCGRs were combined. Surprisingly, independent analysis of KIRs showed a major role of activating KIR 2DS2 for high ADCC levels and prolongation of EFS. The greatest effect was observed in 2DS2-positive patients that also had high-affinity FCGR2A and -3A genotypes. In summary, the presence of the activating KIR 2DS2 has a major effect on ADCC levels and survival in NB patients treated by LTI of ch14.18/CHO and may therefore be a useful biomarker in combination with FCGR polymorphisms for Ab-based immunotherapies.

Generation and Characterization of a Human/Mouse Chimeric GD2-Mimicking Anti-Idiotype Antibody Ganglidiximab for Active Immunotherapy against Neuroblastoma

Vaccination with proteins mimicking GD₂ that is highly expressed on neuroblastoma (NB) cells is a promising strategy in treatment of NB, a pediatric malignancy with poor prognosis. We previously showed efficacy of ganglidiomab in vivo, a murine anti-idiotype (anti-Id) IgG1. In order to tailor immune responses to variable regions, we generated a new human/mouse chimeric anti-Id antibody (Ab) ganglidiximab by replacing murine constant fragments with corresponding human IgG1 regions. DNA sequences encoding for variable regions of heavy (VH) and light chains (VL) were synthesized by RT-PCR from total RNA of ganglidiomab-producing hybridoma cells and further ligated into mammalian expression plasmids with coding sequences for constant regions of human IgG1 heavy and light chains, respectively. We established a stable production cell line using Chinese hamster ovarian (CHO) cells co-transfected with two expression plasmids driving the expression of either ganglidiximab heavy or light chain. After purification from supernatants, anti-idiotypic characteristics of ganglidiximab were demonstrated. Binding of ganglidiximab to anti-GD₂ Abs of the 14.18 family as well as to NK-92tr cells expressing a GD₂-specific chimeric antigen receptor (scFv(ch14.18)-zeta) was shown using standard ELISA and flow cytometry analysis, respectively. Ganglidiximab binding affinities to anti-GD₂ Abs were further determined by surface plasmon resonance technique. Moreover, binding of anti-GD₂ Abs to the nominal antigen GD₂ as well as GD₂-specific Ab-mediated cytotoxicity (ADCC, CDC) was competitively inhibited by ganglidiximab. Finally, ganglidiximab was successfully used as a protein vaccine in vivo to induce a GD₂-specific humoral immune response. In summary, we report generation and characterization of a new human/mouse chimeric anti-Id Ab ganglidiximab for active immunotherapy against NB. This Ab may be useful to tailor immune responses to the paratope regions mimicking GD₂ overexpressed in NB.

Pharmacokinetics and pharmacodynamics of ch14.18/CHO in relapsed/refractory high-risk neuroblastoma patients treated by long-term infusion in combination with IL-2

Ch14.18 manufactured in Chinese hamster ovary (CHO) cells is currently being evaluated in clinical trials. Short-term infusion (STI) (8-20 h/day; 4-5 days) of 100 mg/m2 ch14.18/CHO (dinutiximab β) per cycle in combination with cytokines is standard treatment of neuroblastoma (NB) patients. As pain is a limiting factor, we investigated a novel delivery method by continuous long-term infusion (LTI) of 100 mg/m2 over 10 days. 53 NB patients were treated with 5-6 cycles of 6 × 106 IU/m2 subcutaneous interleukin-2 (d 1-5, 8-12), LTI of 100 mg/m2 ch14.18/CHO (d 8-18) and 160 mg/m2 oral 13-cis-retinoic acid (d 22-35). Human anti-chimeric antibody (HACA), antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity were determined. With LTI, we observed a maximum concentration of ch14.18/CHO (Cmax) of 12.56 ± 0.68 µg/ml and a terminal half-life time (t1/2 β) of 32.7 ± 16.2 d. The clearance values for LTI and STI of 0.54 ± 0.13 and 0.41 ± 0.29 L/d m2 and area under the serum concentration-time curve (AUC) values of 189.6 ± 41.4 and 284.8 ± 156.8 µg×d/ml, respectively, were not significantly different. Importantly, we detected ch14.18/CHO trough concentration of ≥ 1 µg/ml at time points preceding subsequent antibody infusions after cycle 1, allowing a persistent activation of antibody effector mechanisms over the entire treatment period of 6 months. HACA responses were observed in 10/53 (19%) patients, similar to STI (21%), indicating LTI had no effect on the immunogenicity of ch14.18/CHO. In conclusion, LTI of ch14.18/CHO induced effector mechanisms over the entire treatment period, and may therefore emerge as the preferred delivery method of anti-GD2 immunotherapy to NB patients.

Abstract A032: Immunotherapy with ch14.18/CHO in combination with IL2 is active and effective in high-risk relapsed/refractory neuroblastoma patients

Background: Ganglioside GD2 is a glycolipid highly expressed on neuro-ectodermal tumors including melanoma and neuroblastoma (NB). It is ranked on position 12 of the list of tumor associated antigens by the NCI. Anti-GD2 antibody (Ab) ch14.18/CHO targets this antigen and effectively orchestrates innate immune effector mechanisms against GD2 expressing malignancies. However, one on target effect of anti-GD2 Abs is the induction of neuropathic pain when applied as short term infusion (STI) requiring co-medication with intravenous morphine. Here we investigated whether long-term infusion (LTI) of anti-GD2 Ab ch14.18/CHO may have an improved pain toxicity profile and at the same time mediate an effective immune response in patients (pts) with high risk relapsed/refractory NB which translates to objective clinical responses and an improved survival.

Methods: 97 pts received 6x106 IU/m2 sc IL2 (d1-5; 8-12), LTI of 100 mg/m2 ch14.18/CHO (d8-17) and 160 mg/m2 oral 13-cis-RA (d19-32) in an ongoing SIOPEN Phase II study (APN311-202) (NCT01701479) (44 pts) and a closed single center program (53 pts) (APN311-303). Response assessments followed INRG criteria. Serum ch14.18/CHO concentration-time curves were determined by validated ELISA methods and pharmacokinetics parameter were analyzed using standard non-compartmental methods. Fcγ;-receptor polymorphisms FCGR2A (H131R), -3A (V158F) and -3B (NA1/NA2) and patient-specific antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC) and whole blood cytotoxicity (WBT) responses were determined.

Results: LTI was associated with low pain scores and a decreasing morphine usage compared to STI. Clinical overall responses were 30% (APN311-303) and 31% (APN311-202). The survival update of the APN311-303 cohort revealed a 1-y & 4-y OS of 94.2±3.2% & 60.9±9.0% (median FU 2.9y [0.7-5.2y]) and a 1-y & 4-y PFS of 54.4±6.9% & 32.3%±6.9% (median FU 2.8y [0.7 - 4.9y]). Median TTP was 571d (95% CI: 232.7d). The comparator is the reported historical gold standard for relapsed refractory NB patients with 1-y & 4-y PFS of 19±2% & 8±3% and OS of 56±3% & 14±4% and a median TTP of 63 d (95% CI: 56.8d). NB pts with high affinity FCGR alleles and an increase in ADCC (cut off 15%) are associated with longer PFS and OS rates (p&lt;0.03; p&lt;0.005), supporting NK-cell mediated ADCC as the mechanism of action.

Parameters of immune modulation (CDC, and WBT) and PK of ch14.18/CHO were comparable between APN311-202 and -303 cohorts. PK of ch14.18/CHO was analyzed in cycle 1: Cmax=12.2±0.4μg/ml, t½=8.4±1.1 d, AUC=145.3± 5.8 μg*d/ml, Vdss=9.3±0.5L/m2. A pro-inflammatory cytokine response (IL-2, IL-6, IL-8, IFNγ) translated into the expansion of effector NK- (3x) and T-cells (2x). We observed HACA in 17/97 pts (17.5%) of which only 9/97 (9.3%) were neutralizing with respect to the inhibition of CDC and WBT activity. In HACA negative patients, levels of ch14.18/CHO and functional parameters (CDC and WBT) analyzed before subsequent treatment cycles indicate persistent anti-NB activity for the entire treatment period.

Conclusion: LTI of ch14.18/CHO has an improved pain toxicity profile and at the same time is active and effective in high-risk relapsed/refractory NB.

Citation Format: Holger N. Lode, Dominique Valteau-Couanet, Alberto Garaventa, Juliet Gray, Victoria Castel, Isaac Yaniv, Nikolai Siebert, Christian Jensen, Stefanie Endres, Lena Pill, Christin Eger, Diana Seidel, Madlen Jüttner, Silke Kietz, Karoline Ehlert, Evelyne Janzek, Carla Manzitti, Ina Müller, Hans Loibner, Ruth Ladenstein. Immunotherapy with ch14.18/CHO in combination with IL2 is active and effective in high-risk relapsed/refractory neuroblastoma patients. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A032.

Disialoganglioside-specific human natural killer cells are effective against drug-resistant neuroblastoma

The disialoganglioside GD2 is a well-established target antigen for passive immunotherapy in neuroblastoma (NB). Despite the recent success of passive immunotherapy with the anti-GD2 antibody ch14.18 and cytokines, treatment of high-risk NB remains challenging. We expanded the approach of GD2-specific, antibody-based immunotherapy to an application of a GD2-specific natural killer (NK) cell line, NK-92-scFv(ch14.18)-zeta. NK-92-scFv(ch14.18)-zeta is genetically engineered to express a GD2-specific chimeric antigen receptor generated from ch14.18. Here, we show that chimeric receptor expression enables NK-92-scFv(ch14.18)-zeta to effectively lyse GD2(+) NB cells also including partially or multidrug-resistant lines. Our data suggest that recognition of GD2 by the chimeric receptor is the primary mechanism involved in NK-92-scFv(ch14.18)-zeta-mediated lysis and is independent of activating NK cell receptor/ligand interactions. Furthermore, we demonstrate that NK-92-scFv(ch14.18)-zeta is able to mediate a significant anti-tumor response in vivo in a drug-resistant GD2(+) NB xenograft mouse model. NK-92-scFv(ch14.18)-zeta is an NB-specific NK cell line that has potential for future clinical development due to its high stability and activity toward GD2(+) NB cell lines.

Abstract CT410: Immune activation, clinical response and survival following long-term infusion of anti-GD2 antibody ch14.18/CHO in combination with interleukin-2 in high-risk neuroblastoma patients

Purpose: Immunotherapy with monoclonal anti-GD2 antibody (mAb) ch14.18 in combination with cytokines effectively prolonged survival in high risk neuroblastoma (NB). We piloted a less toxic treatment using continuous infusion of ch14.18/CHO in combination with subcutaneous interleukin-2 (IL-2) and report initial clinical response and survival.

Methods and Materials: 53 high risk NB patients received up to 6 cycles of 6x106 IU/m2 s.c. IL-2 (d1-5; 8-12), continuous infusion of 100 mg/m2 ch14.18/CHO (d8-17) and 160 mg/m2 oral 13-cis-RA (d19-32) in a single center compassionate use program. Killer immunoglobulin-like receptor (KIR)/KIR-ligand (KIRL) mismatch and Fcγ-receptor (FCGR) was analyzed with a validated PCR-based analysis of KIR, HLA, FCGR2A (H131R), -3A (V158F) and -3B (NA1/NA2) polymorphisms. Antibody levels and GD2 specific killing of neurpblastoma cells by ADCC, CDC, and whole blood were sequentially analyzed. Clinical response was assessed by mIBG, MRI/CT, bone marrow- and catecholamine- analysis before, after 2/3 and after 5/6 cycles of immunotherapy in patients with measurable disease.

Results: : In the patients receiving ch14.18/CHO continuous infusions significantly less i.v. morphine was used compared to patients who receive ch14.18/CHO bolus infusions. In many patients it was possible to discontinue i.v. morphine and to treat pain with oral Gabapentin only. Response rates were 41.7 % in mIBG (15/36), 31.8 % MRI/CT (7/22), 28.6 % bone marrow- (6/21) and 38.1 % in catecholamine- (8/21) measurements. External review of mIBG responses of 28 patients confirmed a 32.1% response rate (9/28). The overall response following INRG guide lines was determined at 30% (12/40). The event-free-survival rate in the entire cohort was 32.4 % (observation 3.2 years, mean: 1.6 years) and an overall-survival rate of 66.8% (observation 3.9 years, mean: 3.1 years). Patients with KIR/KIRL mismatch and high affinity FCGR alleles showed a trend towards longer event-free survival (P = 0.08), which supports NK cell mediated antibody dependent cytotoxicity as the mechanism of action. Determination of antibody levels and functional immune parameters (ADCC, CDC and WBT) indicate persistent anti-neuroblastoma immune-activity measurable before susequent treatment cycles.

Conclusion: Continuous infusion of anti-GD2 Ab ch14.18/CHO reduces the pain side effect, shows clinical activity in NB patients and improves the outcome. Analysis of KIR/KIRL-mismatch and FCGR-polymorphisms by genotyping may predict clinical outcome in patients receiving ch14.18/CHO. Functional immune parameters indicate anti-neuroblastoma activity over the entire treatment period. These results are subject to prospective confirmation in a SIOPEN Phase II study (EudraCT: 2009-018077-31).

Citation Format: Holger Lode, Christian Jensen, Nikolai Siebert, Silke Kietz, Karoline Ehlert, Ina Müller, Ruth Ladenstein, Evelyne Janzek, Hans Loibner. Immune activation, clinical response and survival following long-term infusion of anti-GD2 antibody ch14.18/CHO in combination with interleukin-2 in high-risk neuroblastoma patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT410. doi:10.1158/1538-7445.AM2014-CT410

Functional bioassays for immune monitoring of high-risk neuroblastoma patients treated with ch14.18/CHO anti-GD2 antibody

Effective treatment of high-risk neuroblastoma (NB) remains a major challenge in pediatric oncology. Human/mouse chimeric monoclonal anti-GD₂ antibody (mAb) ch14.18 is emerging as a treatment option to improve outcome. After establishing a production process in Chinese hamster ovary (CHO) cells, ch14.18/CHO was made available in Europe for clinical trials. Here, we describe validated functional bioassays for the purpose of immune monitoring of these trials and demonstrate GD₂-specific immune effector functions of ch14.18/CHO in treated patients. Two calcein-based bioassays for complement-dependent- (CDC) and antibody-dependent cellular cytotoxicity (ADCC) were set up based on patient serum and immune cells tested against NB cells. For this purpose, we identified LA-N-1 NB cells as best suited within a panel of cell lines. Assay conditions were first established using serum and cells of healthy donors. We found an effector-to-target (E:T) cell ratio of 20∶1 for PBMC preparations as best suited for GD₂-specific ADCC analysis. A simplified method of effector cell preparation by lysis of erythrocytes was evaluated revealing equivalent results at an E:T ratio of 40∶1. Optimal results for CDC were found with a serum dilution at 1∶8. For validation, both within-assay and inter-assay precision were determined and coefficients of variation (CV) were below 20%. Sample quality following storage at room temperature (RT) showed that sodium-heparin-anticoagulated blood and serum are stable for 48 h and 96 h, respectively. Application of these bioassays to blood samples of three selected high-risk NB patients treated with ch14.18/CHO (100 mg/m²) revealed GD₂-specific increases in CDC (4.5–9.4 fold) and ADCC (4.6–6.0 fold) on day 8 compared to baseline, indicating assay applicability for the monitoring of multicenter clinical trials requiring sample shipment at RT for central lab analysis.

Validated detection of human anti-chimeric immune responses in serum of neuroblastoma patients treated with ch14.18/CHO

Human/mouse chimeric monoclonal antibody (mAb) ch14.18/CHO is directed against disialoganglioside GD2. Activity and efficacy of this mAb are currently determined in ongoing clinical Phase II and -III studies in high-risk neuroblastoma (NB). Based on the chimeric nature of this mAb, some patients may develop a human anti-chimeric immune response (Mirick et al., 2004) which impacts on pharmacokinetics and may induce anti-anti-idiotype (Id) mAb with a potential survival benefit. Therefore, a validated method of quantitative detection of human anti-chimeric antibodies (HACA) in serum samples of NB patients treated with ch14.18/CHO is an important tool for monitoring of clinical trials. Here, we report a validated sandwich enzyme-linked immunosorbent assay (ELISA) according to the one arm binding principle using ch14.18/CHO as a capture mAb and biotinylated ch14.18/CHO mAb for detection. Ganglidiomab, a monoclonal anti-Id Ab to ch14.18/CHO (Lode et al., 2013), was used as a standard for assay validation and HACA quantification. Systematic evaluation of the established ELISA procedure revealed an optimal serum sample dilution factor of 1:160. Assay validation was accomplished with a set of tailored quality controls (QC) containing distinct concentrations of ganglidiomab (3 and 15μg/ml). The coefficients of variation (CV) for all within-assay and inter-assay measurements using QCs were under 20% and the limit of detection (LOD) was 1.1μg/ml. Three patients (P1, P2, P3) treated with a 10day continuous infusion of 100mg/m(2) of ch14.18/CHO were selected for analysis with this assay. Selection was based on ch14.18/CHO drug level on day 8 in cycle 2 of >10μg/ml (expected) (P1) and of <2μg/ml (unexpected) (P2 and P3). Both patients with unexpected low ch14.18/CHO levels revealed a strong signal in the HACA ELISA. Interestingly, ch14.18/CHO-mediated complement-dependent cytotoxicity (CDC) could not be detected in P2 in contrast to P3 suggesting anti-NB activity even in the presence of HACA. We showed that neither eight freeze-thaw cycles nor storage at room temperature for up to 168h affected HACA stability in serum. In summary, we describe a validated ELISA method suitable for the assessment of HACA in NB patients treated with ch14.18/CHO.

Validated detection of anti-GD2 antibody ch14.18/CHO in serum of neuroblastoma patients using anti-idiotype antibody ganglidiomab

Human/mouse chimeric monoclonal antibody (mAb) ch14.18 is directed against disialoganglioside GD2 and has demonstrated activity and efficacy in high-risk neuroblastoma (NB). For the purpose of industrial production, ch14.18 was manufactured in Chinese hamster ovarian cells (ch14.18/CHO) in order to facilitate clinical trials in Europe. To determine immunopharmacological effects of ch14.18 in preclinical models and clinical trials, a validated method of quantitative detection of ch14.18/CHO in serum is an important tool. We recently described the generation and characterization of ganglidiomab, a monoclonal anti-idiotype Ab (AIT) of ch14.18 (Lode et al., 2013), which was used to establish quantitative and validated enzyme-linked immunosorbent assay (ELISA) methods using ganglidiomab as a capture mAb. With these ELISA methods, we first demonstrated binding of ch14.18/CHO to ganglidiomab to a similar extent as to the nominal antigen GD2 and in contrast to GD1b and GM2 precursor and metabolite gangliosides, used as negative controls. In order to determine both low (0.5-3.1 μg/ml) and high levels of ch14.18/CHO (1.0-25 μg/ml) in the serum of NB patients treated with ch14.18/CHO, we established two ELISA methods with high and low sensitivity using 1/1001, and 1/5126 sample dilutions, respectively. For validation, we used a set of tailored quality controls (QC) containing distinct concentrations of ch14.18/CHO (1.0, 2.0, 7.0, and 20.0 μg/ml). We determined the limit of detection (LOD) for both ELISA methods to be 0.50 μg/ml for the high sensitivity and 1.02 μg/ml for low sensitivity ELISA. The within-assay precision was 12% for high and 4% for low sensitivity ELISA, and the coefficients of variation (CV) were under 20% for all assays (3% for QC-1.0, 5% for QC-2.0, 7% for QC-7, and 3% for QC-20). With this method, we showed that neither eight freeze-thaw cycles nor storage at room temperature for up to 168 h affected ch14.18/CHO stability in serum. Finally, we analyzed ch14.18 Ab serum levels in selected NB patients receiving ch14.18/CHO as a continuous or bolus infusion with a peak concentration at the last day of Ab application (17.14 ± 7.20mg/ml with continuous and 19.78 ± 2.26 mg/ml with bolus infusion). In summary, we describe validated ELISA methods using ganglidiomab as a capture mAb suitable for the pharmacological evaluation of ch14.18/CHO in NB patients.

Vaccination with anti-idiotype antibody ganglidiomab mediates a GD(2)-specific anti-neuroblastoma immune response

PURPOSE

Immunotherapy targeting disialoganglioside GD(2) emerges as an important treatment option for neuroblastoma, a pediatric malignancy characterized by poor outcome. Here, we report the induction of a GD(2)-specific immune response with ganglidiomab, a new anti-idiotype antibody to anti-GD(2) antibodies of the 14.18 family.

EXPERIMENTAL DESIGN AND RESULTS

Ganglidiomab was generated following immunization of Balb/c mice with 14G2a, and splenocytes were harvested to generate hybridoma cells. Clones were screened by ELISA for mouse antibody binding to hu14.18. One positive clone was selected to purify and characterize the secreted IgG protein (κ, IgG(1)). This antibody bound to anti-GD(2) antibodies 14G2a, ch14.18/CHO, hu14.18, and to immunocytokines ch14.18-IL2 and hu14.18-IL2 as well as to NK-92 cells expressing scFv(ch14.18)-zeta receptor. Binding of these anti-GD(2) antibodies to the nominal antigen GD(2) as well as GD(2)-specific lysis of neuroblastoma cells by NK-92-scFv(ch14.18)-zeta cells was competitively inhibited by ganglidiomab, proving GD(2) surrogate function and anti-idiotype characteristics. The dissociation constants of ganglidiomab from anti-GD(2) antibodies ranged from 10.8 ± 5.01 to 53.5 ± 1.92 nM as determined by Biacore analyses. The sequences of framework and complementarity-determining regions of ganglidiomab were identified. Finally, we demonstrated induction of a GD(2)-specific humoral immune response after vaccination of mice with ganglidiomab effective in mediating GD(2)-specific killing of neuroblastoma cells.

CONCLUSION

We generated and characterized a novel anti-idiotype antibody ganglidiomab and demonstrated activity against neuroblastoma.