Development of a precision immunovirotherapy expressing a folate receptor α bispecific immune cell engager for treatment of ovarian cancer

The biology and silent spread of ovarian cancer make systemic therapy fail rapidly while complete surgical resection is often not possible. Immunotherapies provide a much-needed alternative to standard treatment options. We developed a precision virotherapy utilising an αvβ6 integrin selective adenovirus type 5 virus, Ad5NULL-A20 expressing a bispecific T-cell engager binding Folate receptor alpha (FLOR1), both overexpressed on ovarian cancer, to activate T-cells leading to enhanced immune mediated cancer cell regression.

The efficacy of the newly developed immunovirotherapy was tested in vitro in ovarian cancer lines and ex vivo ascites co-cultured with healthy donor peripheral blood mononuclear cells (PMBCs). T-cell activation was assessed in conjunction with IFN-gamma and TNF-alpha secretion by ELISA and cell viability assays determine cancer cell killing.

Ad5NULL-A20.αFLOR1XCD3 was successfully developed and validated. Co-culture assays with PBMCs show an increase in T-cell activation of up to 80% following transduction with the engineered virotherapy. Increased levels of IFN-gamma and TNF-alpha was evident in cells expressing the bispecific compared to untreated cells. Cell viability assays indicate around 50% decrease in cancer cell viability following virus transduction. In addition, FOLR1 positive ascites-derived ovarian cancer models were established from patients and used for testing the efficacy of the viral vectors ex vivo confirming T-cell activation and cancer cell regression when treated with Ad5NULL-A20.αFLOR1XCD3.

Results indicate Ad5NULL-A20.αFLOR1XCD3 leads to T-cell activation and immune mediated tumour killing in vitro and ex vivo. This novel approach has the potential to become a much-needed alternative treatment option for patients with advanced ovarian cancer.