S100A9‐Targeted Cowpea Mosaic Virus as a Prophylactic and Therapeutic Immunotherapy against Metastatic Breast Cancer and Melanoma

Abstract Prognosis and treatment of metastatic cancer continues to be one of the most difficult and challenging areas of oncology. Treatment usually consists of chemotherapeutics, which may be ineffective due to drug resistance, adverse effects, and dose‐limiting toxicity. Therefore, novel approaches such as immunotherapy have been investigated to improve patient outcomes and minimize side effects. S100A9 is a calcium‐binding protein implicated in tumor metastasis, progression, and aggressiveness that modulates the tumor microenvironment into an immunosuppressive state. S100A9 is expressed in and secreted by immune cells in the pre‐metastatic niche, as well as, post‐tumor development, therefore making it a suitable targeted for prophylaxis and therapy. In previous work, it is demonstrated that cowpea mosaic virus (CPMV) acts as an adjuvant when administered intratumorally. Here, it is demonstrated that systemically administered, S100A9‐targeted CPMV homes to the lungs leading to recruitment of innate immune cells. This approach is efficacious both prophylactically and therapeutically against lung metastasis from melanoma and breast cancer. The current research will facilitate and accelerate the development of next‐generation targeted immunotherapies administered as prophylaxis, that is, after surgery of a primary breast tumor to prevent outgrowth of metastasis, as well as, therapy to treat established metastatic disease.