Project Funding Details

Vascular endothelial growth factor receptor-1 (VEGFR-1) is a tyrosine kinase receptor for VEGF-A and placental growth factor (PlGF), expressed by endothelial, myelomonocytic and tumor cells. Differently from VEGFR-2, VEGFR-1 is not required for physiological angiogenesis in adults. Involvement of VEGFR-1 and PlGF in pathological angiogenesis, tumor invasiveness and infiltration by protumoral M2 macrophages renders this receptor a suitable target for cancer treatment, avoiding the systemic toxicity associated with VEGFR-2/VEGF-A inhibitors. VEGFR-1 and PlGF are expressed in glioblastoma (GBM), where they promote extra-cellular matrix invasion and anti-VEGF-A resistance. GBM is a highly aggressive brain cancer with remarkable infiltrative behavior, angiogenesis, and immunosuppressive tumor microenvironment (TME). Despite treatment with surgery, radiotherapy and temozolomide, patients' survival is extremely short. We generated a murine anti-human VEGFR-1 monoclonal IgG1 antibody (D16F7 mAb) that inhibits membrane receptor signaling without affecting VEGF-A/PlGF binding. A unique property of D16F7 is its ability of preserving the decoy/anti-angiogenic function of soluble VEGFR-1, which sequesters VEGF-A/PlGF in the TME. Our data in a murine GBM orthotopic model indicate that D16F7 exerts antitumor activity without adverse effects. Since mAb humanization is a requisite for clinical development, we have obtained a humanized hD16F7 mAb. Considering VEGFR-1 expression in tumor cells, microglia, M2 macrophages, tumor endothelium, and the reported decrease of soluble VEGFR-1/VEGF-A ratio in GBM due to increased VEGF-A, we hypothesize that a treatment based on a mAb with the D16F7 properties may reduce GBM aggressiveness. Aim of the study is to validate the efficacy of VEGFR-1 targeting by hD16F7, as monotherapy or combined with temozolomide, as prototype for future clinical development. Moreover, antibody-drug conjugates (ADCs) derived from hD16F7 that selectively deliver toxic molecules to VEGFR-1 positive GBM cells, tumor-associated microglia and macrophages will be investigated. Since biologics with lower molecular weight and lacking the Fc region have improved brain penetration and lower brain efflux, the efficacy of a single-chain fragment variable (scFv) derived from hD16F7 will be also evaluated. The project comprises four work-packages, including in vitro and in vivo preclinical studies. We will characterize hD16F7 and scFv ability to inhibit invasiveness of immortalized human GBM cell lines and primary cultures in response to VEGF-A and PlGF, and to modulate the immunosuppressive TME by using organoids established from surgical tumor samples collected from patients. Immune-mediated mechanisms contributing to hD16F7 antitumor activity will be also investigated. Cytotoxicity of anti-VEGFR-1 ADCs conjugated with MMAE or PBD will be assayed against GBM cultures and organoids. In vivo testing of hD16F7 or scFv (+/- temozolomide) and an ADC will be performed in xenografts generated from GBM patient-derived organoids. Demonstration of anti-VEGFR-1 hD16F7 mAb, scFv and ADCs inhibitory activity on GBM properties that contribute to tumor aggressiveness by using in vitro and in vivo models that more closely reflect clinical response. Results may also contribute to establish the predictive role of organoids for evaluating new therapies. GBM treatment is still an unmet medical need and humanized mAb/scFv/ADCs targeting tumor cells, immunosuppressive TME and pathological angiogenesis might represent an alternative or adjunct therapy for this aggressive cancer.