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Neuroblastoma evolution, heterogeneity, and resistance remain inadequately defined, suggesting a role for circulating tumor DNA (ctDNA) sequencing. To define the utility of ctDNA profiling in neuroblastoma, 167 blood samples from 48 high-risk patients were evaluated for ctDNA using comprehensive genomic profiling. At least one pathogenic genomic alteration was identified in 56% of samples from 73% of evaluable patients, including clinically actionable ALK and RAS-MAPK pathway variants. Fifteen patients received ALK inhibition (ALKi) and ctDNA data revealed dynamic genomic evolution under ALKi therapeutic pressure. Serial ctDNA profiling detected disease evolution in 15 of 16 patients with a recurrently identified variant, in some cases confirming disease progression prior to standard surveillance methods. Finally, ctDNA-defined ERRFI1 loss-of-function variants were validated in neuroblastoma cellular models, with the mutant proteins exhibiting loss of wild-type ERRFI1’s tumor suppressive functions. Taken together, ctDNA is prevalent in children with high-risk neuroblastoma and should be followed throughout neuroblastoma treatment.

BackgroundAntibody–drug conjugates (ADCs) that deliver cytotoxic drugs to tumor cells have emerged as an effective and safe anticancer therapy. ADCs may induce immunogenic cell death (ICD) to promote additional endogenous antitumor immune responses. Here, we characterized the immunomodulatory properties of D3-GPC2-PBD, a pyrrolobenzodiazepine (PBD) dimer-bearing ADC that targets glypican 2 (GPC2), a cell surface oncoprotein highly differentially expressed in neuroblastoma.MethodsADC-mediated induction of ICD was studied in GPC2-expressing murine neuroblastomas in vitro and in vivo. ADC reprogramming of the neuroblastoma tumor microenvironment was profiled by RNA sequencing, cytokine arrays, cytometry by time of flight and flow cytometry. ADC efficacy was tested in combination with macrophage-driven immunoregulators in neuroblastoma syngeneic allografts and human patient-derived xenografts.ResultsThe D3-GPC2-PBD ADC induced biomarkers of ICD, including neuroblastoma cell membrane translocation of calreticulin and heat shock proteins (HSP70/90) and release of high-mobility group box 1 and ATP. Vaccination of immunocompetent mice with ADC-treated murine neuroblastoma cells promoted T cell-mediated immune responses that protected animals against tumor rechallenge. ADC treatment also reprogrammed the tumor immune microenvironment to a proinflammatory state in these syngeneic neuroblastoma models, with increased tumor trafficking of activated macrophages and T cells. In turn, macrophage or T-cell inhibition impaired ADC efficacy in vivo, which was alternatively enhanced by both CD40 agonist and CD47 antagonist antibodies. In human neuroblastomas, the D3-GPC2-PBD ADC also induced ICD and promoted tumor phagocytosis by macrophages, which was further enhanced when blocking CD47 signaling in vitro and in vivo.ConclusionsWe elucidated the immunoregulatory properties of a GPC2-targeted ADC and showed robust efficacy of combination immunotherapies in diverse neuroblastoma preclinical models.

Programmed cell death protein 1 (PD‐1) is an immunoregulatory target which is recognized by different monoclonal antibodies, approved for the therapy of multiple types of cancer. Different anti‐PD‐1 antibodies display different therapeutic properties and there is a pharmaceutical interest to generate and characterize novel anti‐PD‐1 antibodies. We screened multiple human antibody phage display libraries to target novel epitopes on the PD‐1 surface and we discovered a unique and previously undescribed binding specificity (termed D12) from a new antibody library (termed AMG). The library featured antibody fragments in single‐chain fragment variable (scFv) format, based on the IGHV3‐23*03 (VH) and IGKV1‐39*01 (Vκ) genes. The D12 antibody was characterized by surface plasmon resonance (SPR), cross‐reacted with the Cynomolgus monkey antigen and bound to primary human T cells, as shown by flow cytometry. The antibody blocked the PD‐1/PD‐L1 interaction in vitro with an EC50 value which was comparable to the one of nivolumab, a clinically approved antibody. The fine details of the interaction between D12 and PD‐1 were elucidated by x‐ray crystallography of the complex at a 3.5 Å resolution, revealing an unprecedented conformational change at the N‐terminus of PD‐1 following D12 binding, as well as partial overlap with the binding site for the cognate PD‐L1 and PD‐L2 ligands which prevents their binding. The results of the study suggest that the expansion of antibody library repertoires may facilitate the discovery of novel binding specificities with unique properties that hold promises for the modulation of PD‐1 activity in vitro and in vivo.