LGALS3BP antibody-drug conjugate enhances tumor-infiltrating lymphocytes and synergizes with immunotherapy to restrain neuroblastoma growth

Background: LGALS3BP, also referred as Gal-3BP, Mac2-BP, or 90 K, is a heavily glycosylated, secreted protein prominently localized at the surface of cancer-derived extracellular vesicles (EVs). Its levels are significantly elevated in various types of cancer, including neuroblastoma, and are generally associated with advanced disease and tumor progression. Our previous research has shown that LGALS3BP is an effective target for ravtansine (DM4)-based Antibody-Drug Conjugate (ADC) therapy in multiple preclinical models. Methods: We assessed total and extracellular vesicles (EVs)-associated LGALS3BP through ELISA assay in serum of a pseudometastatic neuroblastoma model to evaluate the correlation of LGALS3BP levels with tumor dissemination. We employed a syngeneic neuroblastoma mouse model using murine neuroblastoma NXS2 cells overexpressing human LGALS3BP in order to evaluate immunogenic cell death (ICD) induced by anti-LGALS3BP ADC therapy and investigated the nature of the tumor immune infiltrate by cytofluorimetry. Furthermore, we designed a six-arm in vivo experiment to evaluate the efficacy of ADC in combination with an immune check-point inhibitor (ICI) anti-PD-1. Finally, a rechallenge assay was conducted on cured mice to assess the presence of immunological memory. Results: Here, we report that circulating and EVs-associated LGALS3BP levels significantly correlate with neuroblastoma progression and dissemination. Moreover, we show that in the syngeneic NXS2 neuroblastoma model, DM4 treatment induces cell surface expression of ICD markers calreticulin, HSP70, and HSP90, and an increased PD-L1 expression in vitro, followed by enhanced tumor-infiltrating lymphocytes in vivo. Notably, the combination therapy of anti-LGALS3BP-targeting ADC with anti-PD-1 results in a higher inhibition of tumor growth and prolonged survival compared with either agent given alone. Rechallenge assay reveals that mice previously treated and cured with the ADC retain immune memory, suggesting the therapy's ability to induce a durable and protective antitumor immune response. Conclusions: Our findings establish that circulating LGALS3BP is a potential biomarker for liquid biopsy and uncover this protein as a suitable target for therapeutic strategies combining 1959-sss/DM4 ADC with an anti-PD-1 ICI for the treatment of LGALS3BP expressing neuroblastoma.