Abstract LB085: ATYR2810, a fully humanized monoclonal antibody targeting the VEGF-NRP2 pathway sensitizes highly aggressive and chemoresistant TNBC subtypes to chemotherapy
Authors: Xu Zhiwen , Barber Alison , Burkart Christoph , Goel Hira Lal , Rahman Justin , Hamel Kristina , Fogassy Zachary , Eide Lisa , Polizzi Clara , Stamps Jasmine , Savino Sofia Klopp , Burman Luke , Chong Esther , Paz Suzanne , Mercurio Arthur M. , Nangle Leslie A. 
Published: June 2022

Abstract
Introduction: Triple negative breast cancer (TNBC) represents 15% of all breast cancers, and is a notably aggressive subtype that is prone to early recurrence following initial diagnosis with a median survival of only 9 months following recurrence. One of the few treatment options for patients with advanced and metastatic TNBC is platinum-based chemotherapy, however not all tumors respond, and those that do often become refractory during the course of treatment. The cell surface receptor Neuropilin-2 (NRP2), which acts as a co-receptor for vascular endothelial growth factors (VEGFs), has been shown to be both highly expressed and associated with therapeutic resistance in TNBC. NRP2 also serves as a co-receptor for semaphorins, which may play tumor-suppressor functions in breast cancer. We have previously demonstrated that ATYR2810, a highly specific humanized monoclonal antibody which effectively blocks NRP2/VEGF signaling without disrupting NRP2/Semaphorin 3F signaling, down-regulated epithelial-mesenchymal transition (EMT) genes such as ZEB1 and sensitizes TNBC to chemotherapy both in vitro and in vivo.
Results: In this study we have further characterized the breast cancer subtypes that are most responsive to ATYR2810 treatment. Using in vitro 3D colony formation assays (CFAs), we have interrogated ~15 breast cancer cell lines covering luminal, HER2+ and various TNBC subtypes, for responsiveness to ATYR2810 treatment in combination with chemotherapy. All responsive cell lines were associated with the more aggressive subtypes of TNBC such as BL2 (basal-like 2), ML (mesenchymal-like) and MSL (mesenchymal-stem like) subtypes. Additionally, we screened five patient derived xenografts (PDXs) and again found that the responsive PDXs were associated with the more aggressive and chemoresistant subtypes of TNBC. To gain insight into the potential mechanism for enhanced chemosensitivity by ATYR2810 treatment, we performed RNAseq on the PDX tumors. Interestingly, the chemokine receptor CXCR4, which is known to promote drug resistance and tumorigenic potential, was found to be significantly downregulated in responder PDX tumors treated with ATYR2810 in combination with cisplatin as compared to those treated with cisplatin alone. Further, gene set enrichment analysis (GSEA) showed that CXCR4 was found in numerous downregulated pathways enriched in the PDX responder tumors treated with ATYR2810/cisplatin, suggesting that CXCR4 may be driving the responder phenotype of the PDXs. Flow cytometry analysis of TNBC cells treated with ATYR2810 monotherapy in vitro resulted in a reduced frequency of cells expressing CXCR4. Furthermore, ATYR2810 monotherapy inhibited spontaneous lung metastasis in experimental models of mesenchymal TNBC.
Conclusion: Taken together, our data suggest that ATYR2810 enhances chemosensitivity in highly aggressive TNBC subtypes, and that this response may be mediated through the downregulation of genes known to be associated with aggressive cancer states such as ZEB1 and CXCR4. ATYR2810 may therefore serve as a novel therapeutic agent for the treatment of advanced and metastatic TNBC and potentially other aggressive cancer types.
Zhiwen Xu and Alison Barber are co-first authors of this abstract.
Citation Format: Zhiwen Xu, Alison Barber, Christoph Burkart, Hira Lal Goel, Justin Rahman, Kristina Hamel, Zachary Fogassy, Lisa Eide, Clara Polizzi, Jasmine Stamps, Sofia Klopp Savino, Luke Burman, Esther Chong, Suzanne Paz, Arthur M. Mercurio, Leslie A. Nangle. ATYR2810, a fully humanized monoclonal antibody targeting the VEGF-NRP2 pathway sensitizes highly aggressive and chemoresistant TNBC subtypes to chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB085.