Lectikines for Immunotherapy against Ovarian Cancer - SUMMARY The goal of this project is to create a novel immunotherapeutic drug candidate against ovarian cancer (OVCA). OVCA is the leading cause of death from gynecological malignancy in the United States, with poor survival rates due to late diagnosis and chemo-resistant, fatal recurrent disease after the first-line debulking surgery and chemotherapies. Immune checkpoint inhibitors have thus far failed to show a significant clinical benefit due to highly immunosuppressive tumor microenvironment and poor infiltration of T cells. Thus, the development of effective OVCA immunotherapy requires novel strategies. To address this problem, the proposed project will create novel immunotherapeutic proteins based on Avaren lectin. It is a small, 14-kDa recombinant protein engineered in the PI’s laboratory from a natural actinomycete lectin, which selectively recognizes a cluster of high-mannose glycans that are prevalent on the surface of enveloped viruses and malignant cells. A fusion protein consisting of Avaren lectin and human IgG1 Fc (AvFc) was previously shown to exhibit potent antiviral and antitumor activities without toxicity in in vitro and in vivo animal models. Based on growing evidence indicating that high-mannose overaccumulation also occurs on the surface of OVCA cells, we hypothesize that Avaren lectin can be utilized in novel OVCA-targeting strategies. Our preliminary data show that AvFc efficiently binds to OVCA but not to adjacent normal tissues. AvFc elicited potent antibody-dependent cell-mediated cytotoxicity (ADCC) against OVCA cell lines. Furthermore, AvFc treatment exhibited moderate yet statistically significant efficacy extending the survival of animals in a syngeneic, orthotopic murine OVCA model using the ID8 cell line. Building on these data, in this project we will create immunostimulatory variants of Avaren lectin that can transform OVCA into more immunologically hot tumors, thereby exhibiting potent immunotherapeutic efficacy. Specifically, we will engineer translational fusion proteins consisting of Avaren lectin / AvFc and an antitumor cytokine (“lectikines”). In Aim 1, we will generate lectikines by fusing a variant of IL-2 devoid of CD25 binding (IL-2v) or IL-15 to AvFc, which will be produced in Nicotiana benthamiana plants using a transient overexpression system. After thorough purification, we will assess their molecular properties, OVCA cell-binding affinity and cytokine functions in a battery of biochemical, biophysical and cell-based assays. In Aim 2, we will evaluate the therapeutic effects of lectikines in comparison with AvFc in a murine ID8 OVCA model. Disease progression will be monitored through abdomen circumference, body weight, and live animal bioluminescence imaging. Immunophenotyping of peritoneal cells will be performed by flow cytometry. We anticipate that lectikines will elicit significant efficacy through increased immune activation in the tumor microenvironment. Successful completion of this pilot project will establish an initial proof-of-concept and generate a compelling data set for further investigation and development of a first-in-class OVCA immunotherapy.
