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

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.

Design and Characterization of an "All-in-One" Lentiviral Vector System Combining Constitutive Anti-GD2 CAR Expression and Inducible Cytokines

Genetically modified T cells expressing chimeric antigen receptors (CARs) so far have mostly failed in the treatment of solid tumors owing to a number of limitations, including an immunosuppressive tumor microenvironment and insufficient CAR T cell activation and persistence. Next-generation approaches using CAR T cells that secrete transgenic immunomodulatory cytokines upon CAR signaling, known as TRUCKs (“T cells redirected for universal cytokine-mediated killing”), are currently being explored. As TRUCKs were engineered by the transduction of T cells with two separate vectors, we developed a lentiviral modular “all-in-one” vector system that combines constitutive CAR expression and inducible nuclear factor of activated T cells (NFAT)-driven transgene expression for more efficient production of TRUCKs. Activation of the G_D2-specific CAR via GD2⁺ target cells induced NFAT promoter-driven cytokine release in primary human T cells, and indicated a tight linkage of CAR-specific activation and transgene expression that was further improved by a modified NFATsyn promoter. As proof-of-concept, we showed that T cells containing the “all-in-one” vector system secrete the immunomodulatory cytokines interleukin (IL)12 or IL18 upon co-cultivation with primary human GD2⁺ tumor cells, resulting in enhanced effector cell properties and increased monocyte recruitment. This highlights the potential of our system to simplify application of TRUCK-modified T cells in solid tumor therapy.

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.

Quantification of total dinutuximab concentrations in neuroblastoma patients with liquid chromatography tandem mass spectrometry

Neuroblastoma is one of the most commonly found solid tumors in children. The monoclonal antibody dinutuximab (DNX) targets the sialic acid-containing glycosphingolipid GD2 expressed on almost all neuroblastoma tumor cells and induces cell lysis. However, the expression of GD2 is not limited to tumor cells only, but is also present on central nerve tissue and peripheral nerve cells explaining dinutuximab toxicity. The most common adverse reactions are pain and discomfort, which may lead to discontinuation of the treatment. Furthermore, there is little to no data available on exposure and effect relationships of dinutuximab. We, therefore, developed an easy method in order to quantify dinutuximab levels in human plasma. Ammonium sulfate (AS) was used to precipitate all immunoglobulins (IgGs) in human plasma. After centrifugation, supernatant containing albumin was decanted and the precipitated IgG fraction was re-dissolved in a buffer containing 0.5% sodium dodecyl sulfate (SDS). Samples were then reduced, alkylated, and digested with trypsin. Finally, a signature peptide in complementarity determining region 1 of DNX heavy chain was quantified on LC-MS/MS using a stable isotopically labeled peptide as internal standard. AS purification efficiently removed 97.5% of the albumin fraction in the supernatant layer. The validation performed on DNX showed that within-run and between-run coefficients of variation (CV) for lower limit of quantification (LLOQ) were 5.5 and 1.4%, respectively. The overall CVs for quality control (QC) low, QC med, and QC high levels were < 5%. Linearity in the range 1-32 mg/L was excellent (r2 > 0.999). Selectivity, stability, and matrix effect were in concordance with EMA guidelines. In conclusion, a method to quantify DNX in human plasma was successfully developed. In addition, the high and robust process efficiency enabled the utilization of a stable isotopically labeled (SIL) peptide instead of SIL DNX, which was commercially unavailable. Graphical abstract.

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.

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.

A multifactorial screening strategy to identify anti-idiotypic reagents for bioanalytical support of antibody therapeutics

Antibodies are critical tools for protein bioanalysis; their quality and performance dictate the caliber and robustness of ligand binding assays. After immunization, polyclonal B cells generate a diverse antibody repertoire against constant and variable regions of the therapeutic antibody immunogen. Herein we describe a comprehensive and multifactorial screening strategy to eliminate undesirable constant region-specific antibodies and select for anti-idiotypic antibodies with specificity for the unique variable region. Application of this strategy is described for the therapeutic antibody Mab-A case study. Five different factors were evaluated to select a final antibody pair for the quantification of therapeutics in biological matrices: (i) matrix effect in preclinical and clinical matrices, (ii) assay sensitivity with lower limit of quantification goal of single-digit ng/ml (low pM) at a signal-to-background ratio greater than 5, (iii) epitope distinction or nonbridging antibody pair, (iv) competition with target and inhibitory capacity enabling measurement of free drug, and (v) neutralizing bioactivity using bioassay. The selected antibody pair demonstrated superior assay sensitivity with no or minimal matrix effect in common biological samples, recognized two distinct binding epitopes on the therapeutic antibody variable region, and featured inhibitory and neutralizing effects with respect to quantification of free drug levels.

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.