Abstract 6355: Urokinase plasminogen activator receptor-associated protein (uPARAP) is overexpressed in human glioblastomas and is a therapeutic target for antibody-drug conjugates (ADC)

Abstract

Abstract Background: Glioblastoma Multiforme (GBM), primarily arising in the brain's frontal and temporal lobes, is a devastating malignancy originating from astrocytes. Despite treatment advancements, the prognosis remains bleak, with a median survival of 15-18 months and a 10% five-year survival rate.Our study explored a novel targeted approach to combat this challenge. uPARAP is an endocytic receptor expressed at low levels on selected mesenchymal cell types but highly overexpressed on the majority of Soft-Tissue- and Bone Sarcomas. It internalizes fragments of collagen and transfers them to the lysosome for degradation. Methods & Results: First, we analyzed formalin-fixed paraffin-embedded (FFPE) tumors from GBM patients through immunohistochemistry (IHC) staining. Interestingly, a majority of the samples showed strong but varying uPARAP expression. In parallel, we detected and quantified uPARAP receptor expression in GBM cell lines by flow cytometry, underscoring its potential as a therapeutic target.Next, we generated an antibody-drug conjugate (ADC) linked to monomethyl auristatin E (MMAE), a potent antimitotic agent. Confocal microscopy showed rapid internalization of the ADC in several GBM cell lines in vitro. Cellular cytotoxicity was demonstrated in Incucyte and Alamar Blue in vitro assays. Finally, anti-tumor activity of the uPARAP-ADC was studied in a GBM patient-derived xenograft (PDX) model in vivo, where it resulted in significant tumor regression with a tumor growth inhibition (TGI) of 92 and 97% at 3 and 6 mg/kg, respectively. Conclusions: Our findings show that uPARAP is overexpressed on GBM tumors and that a uPARAP-targeted ADC has anti-tumor activity in a PDX model of GBM. This research provides initial evidence that uPARAP-ADCs could become a novel treatment option for this highly aggressive disease. Citation Format: Ida Gregersen, Cecillie R. Løkke, Jette B. Lange, Pernille Barkholt, Christophé Côme, Tina Broberg, Marianne M. Petersen, Carmel M. Lynch, Dominik Mumberg, Niels Behrendt, Lars H. Engelholm. Urokinase plasminogen activator receptor-associated protein (uPARAP) is overexpressed in human glioblastomas and is a therapeutic target for antibody-drug conjugates (ADC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6355.