Pharmacology of a Plant Virus Immunotherapy Candidate for Peritoneal Metastatic Ovarian Cancer.

Due to the increasing incidence of cancer, there is a need to develop new platforms that can combat this disease. Cancer immunotherapy is a platform that takes advantage of the immune system to recognize and eradicate tumors and metastases. Our lab has identified a plant virus nanoparticle, cowpea mosaic virus (CPMV) as a promising approach for cancer immunotherapy. When administered intratumorally, CPMV relieves the immune system of tumor-induced immunosuppression and reprograms the tumor microenvironment into an activated state to launch systemic antitumor immunity. The efficacy of CPMV has been tested in many tumor models and in canine cancer patients with promising results: tumor shrinkage, systemic efficacy (abscopal effect), and immune memory to prevent recurrence. To translate this drug candidate from the bench to the clinic, studies that investigate the safety, pharmacology, and toxicity are needed. In this work, we describe the efficacy of CPMV against a metastatic ovarian tumor model and investigate the biodistribution of CPMV after single or repeated intraperitoneal administration in tumor-bearing and healthy mice. CPMV shows good retention in the tumor nodules and broad bioavailability with no apparent organ toxicity based on histopathology. Data indicate persistence of the viral RNA, which remains detectable 2 weeks post final administration, a phenomenon also observed with some mammalian viral infections. Lastly, while protein was not detected in stool or urine, RNA was shed through excretion from mice; however, there was no evidence that RNA was infectious to plants. Taken together, the data indicate that systemic administration results in broad bioavailability with no apparent toxicity. While RNA is shed from the subjects, data suggest agronomical safety. This data is consistent with prior reports and provides support for translational efforts.