Abstract A119: Antibody blockade of Semaphorin 4D neutralizes barrier to immune infiltration and facilitates immune-mediated tumor rejection

• Published in: Cancer immunology research 2016-01, Vol.4 (1_Supplement), p.A119-A119
• Main Authors: Evans, Elizabeth E., Bussler, Holm, Torno, Sebold, Mallow, Crystal, Winters, Laurie A., Reilly, Christine, Klimatcheva, Ekaterina, Veeraraghavan, Janaki, Jonason, Alan S., Scrivens, Maria, Kirk, Renee, Howell, Alan, Balch, Leslie, Leonard, John E., Paris, Mark, Fisher, Terrence L., Smith, Ernest S., Zauderer, Maurice
• Format: Article
• Language: English
• ISSN: 2326-6066; 2326-6074
• DOI: 10.1158/2326-6074.CRICIMTEATIAACR15-A119

Semaphorin 4D (SEMA4D, CD100) and its receptor plexin-B1 are broadly expressed in cancer and expression correlates with invasive disease in several human tumors. SEMA4D normally functions to regulate the motility and differentiation of multiple cell types, including those of the immune, vascular, and nervous systems. In the setting of cancer, we describe a novel immunomodulatory function of SEMA4D in regulation of immune cell infiltration and activity in the tumor microenvironment (TME). Purpose: Characterize immune-related and anti-tumor activity mediated by antibody neutralization of SEMA4D, as a single agent and in combination with other immunomodulatory therapies. Methods: Blockade of SEMA4D with monoclonal murine antibody was evaluated in subcutaneous models, as well as an orthotopic ERBB2+ breast carcinoma syngeneic model. Anti-tumor immune response in pre-clinical models was characterized by selective in vivo immune cell depletions, as well as immunohistochemistry, flow cytometry, and functional assays. The safety and tolerability of a humanized anti-SEMA4D antibody VX15/2503 was assessed in Phase I clinical trials in oncology. Results: SEMA4D restricts migration of macrophage cell lines in vitro. Strong expression of SEMA4D at the invasive margins of actively growing in vivo tumors modulates the infiltration and spatial distribution of leukocytes in the TME. Antibody neutralization of SEMA4D disrupts this gradient and facilitates recruitment of potent antigen presenting cells and T lymphocytes into the TME, shifting the balance of cytokines toward increased Th1 and reduced immunosuppressive cytokines. This orchestrated change in the tumor architecture was associated with durable tumor rejection and immunologic memory in preclinical models. Immune-mediated tumor rejection may enhance the disruption of ERBB2 transactivation with SEMA4D receptors, which has been reported for ERBB2 and Met oncogenes. Importantly, the immunomodulatory activity of anti-SEMA4D antibody can also be further enhanced by combination with other immunotherapies, including immune checkpoint inhibition and chemotherapy. Strikingly, the combination of anti-SEMA4D antibody with antibody to CTLA-4 acts synergistically to promote complete tumor rejection and survival, with significant 58% increase in tumor regression and maximal increase in survival, as compared to monotherapy. Treatment with anti-SEMA4D antibodies was well tolerated in nonclinical and clinical studies, including com