Abstract 2913: Personalized ovarian cancer therapy using in vivo assembled bi-specific antibodies targeting Her2 and FSHR

Abstract

Abstract According to The American Cancer Society, ovarian cancer will cause ~14,000 deaths in the US in 2021. Despite recent advances in therapy, clinical outcomes remain poor and there is a great unmet need for newer therapies for ovarian cancer patients. Bispecific T cell engagers (BiTEs) consist of two single chain variable fragments (scFVs) linked via a peptide linker and are being studied as a tool against many different cancers. BiTEs redirect T cell activity towards tumor cells in an MHC independent manner by bringing T cells close to a tumor associated antigen (TAA). A BiTE targeting CD19 has been approved for treating ALL, however the success of BiTEs in treating solid tumor remains limited. Two reasons that reduce the efficacy of BiTEs in solid tumors are 1) their short half-life which drastically reduces their availability 2) tumor heterogeneity preventing targeting by a single BiTE. Tumors downregulate TAA expression in response to targeted therapy allowing treatment escape. Development of novel BiTEs with longer serum half-lives and in vivo delivery strategies which allow rapid customization of BiTEs is important. Here we describe a strategy for in vivo assembly using the Knob-in-hole (KIH) approach. We designed two different DNA encoded KIH (dKIH), targeting Her2 and FSHR, and studied their ability to be assembled in vivo into functional therapeutics. The knobs encoded full length antibodies engineered to target either Her2 or FSHR. We designed a third construct as the hole to target CD3. Following in vitro characterization, we injected NSG mice with KIH pairs for Her2+CD3 or FSHR+ CD3 and studied their expression and function. Sera from mice injected with Her2 or FSHR dKIH bound tumor cells expressing Her2 or FSHR respectively. Sera from mice from both groups also bound to T cells. We observed that both dKIH resulted in mouse sera with high potency (pg level) killing of ovarian cancer cell lines expressing Her2 and FSHR in an in vitro killing assay. A single injection of either dKIH allowed for in vivo expression and tumor killing for over a month post injection which is a significant improvement over delivery of protein KIH. This study demonstrates the potential of in vivo assembly of KIH. The patients produce their own therapy, which allows to skip complex bioprocessing steps and makes KIH delivery simpler and cheaper. This study illustrates the potential to improve immunotherapy outcomes for ovarian cancer patients via in vivo assembly of multiple BiTEs. Citation Format: Pratik Sanjivkumar Bhojnagarwala, Ali Raza Ali, Drew Frase, Abhijeet Kulkarni, Devivasha Bordoloi, David B. Weiner. Personalized ovarian cancer therapy using in vivo assembled bi-specific antibodies targeting Her2 and FSHR [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2913.