P-01.13 SECN-15: An antisense oligonucleotide-based approach to target expression of Neuropilin-1 induces anti-tumor activity in vivo and boosts efficacy of checkpoint inhibitors Knockdown of Neuropilin-1 via antisense oligonucleotides induces anti-t

<h3>Background</h3> The approval of immune checkpoint inhibitors (ICI) has marked a significant breakthrough in the treatment of cancer. Nevertheless, the majority of patients, either is or becomes unresponsive to ICI, indicating an unmet need for new therapies. Neuropilin-1 (NRP1) is a transmembrane protein that interacts with multiple receptors and ligands fostering an immunosuppressive tumor microenvironment (TME). NRP1 is involved in the migration of tumor associated macrophages (TAMs), stabilizes the phenotype of regulatory T cells, is associated with exhaustion of effector T cells and is a mediator of neoangiogenesis. Additionally, high expression of NRP1 has been associated with a poor prognosis in several cancers including gastric, pancreatic, and breast cancer. We used locked nucleic acid (LNA) modified antisense oligonucleotides (ASOs) for the downregulation of NRP1 in murine cancer models and investigated the anti-tumor efficacy as monotherapy and in combination with anti-PD-(L)1 antibodies as an in vivo proof-of-concept. <h3>Materials and Methods</h3> We identified well tolerated NRP1-specific ASOs with high activity using our OligoCreator oligonucleotide discovery platform. The best ASOs were tested in different syngeneic tumor models with palpable tumors already established, as monotherapy as well as in combination with ICIs. We analyzed survival, immune infiltration, NRP1 expression, and transcriptome changes. <h3>Results</h3> We observed robust knockdown of NRP1 in bulk tumor tissue, as well as in individual infiltrating cell types, including T cells and macrophages. Simultaneously, transcriptomic changes in pathways related to inflammation and extracellular matrix remodeling were detected. Mice treated with ICI alone showed only low anti-tumor efficacy, whereas NRP1 specific ASOs delayed tumor growth up to complete tumor eradication. Strikingly, combination of NRP1 ASOs with ICI led to remarkable anti-tumor efficacy. Complete responders from these studies were re-challenged about three months after the last treatment. While treatment-naïve control mice showed rapid tumor growth, all re-challenged mice eradicated tumors quickly, without the need for an additional treatment. <h3>Conclusions</h3> LNA modified ASOs specific for NRP1 hold great promise as a new treatment strategy for solid cancers. We show that the limited efficacy of ICI in the models tested could be improved significantly when combined with the ASO-treatment. A robust knockdown of NRP1 was observed in multiple infiltrating cell types, together with increased expression of genes involved in inflammation and decreased expression of genes involved in extracellular matrix organization, which is currently being further analyzed. Preparations to bring the human NRP1-specific ASO ‘SECN-15’ into the clinic for the treatment of patients with solid cancers are currently underway. <b>A. Maaske:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>S. Michel:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>D. Kokotek:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>D. Kokotek Kirchhammer:</b> B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>A. Sadewasser:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>J. Festag:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>M. Buchi:</b> B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>M. Schell:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>J. Sekar:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>S. Raith:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>A. Zippelius:</b> B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. F. Consultant/Advisory Board; Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>F. Jaschinski:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. <b>R. Klar:</b> A. Employment (full or part-time); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Secarna pharmaceuticals GmbH &amp; Co. KG.