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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.

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.

(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.