Anti-PD-1 therapy has improved therapeutic outcomes of patients in multiple cancer types. However, the therapy has demonstrated clinical benefits in only a small fraction of patients. The reason of the limited response in clinical practice is not fully understood.

In an aim to improve anti-cancer drug delivery and potency, we have been developing in situ delivery and production system (i-DPS) by modifying a non-pathogenic anaerobic bacterium, Bifidobacterium, which localizes and proliferates only in the hypoxic environment like solid tumors after intravenous administration, produces anticancer proteins, enzymes or other pharmacologically active molecules selectively at the tumor site. Here we present anti-human PD-1 antibody scFv producing i-DPS in cancer immunotherapy, which could be specifically delivered to and amplified only at the hypoxic sites of solid tumors. A series of in vitro assays has been performed to confirm the stable expression and secretion of anti-human PD-1 scFv by recombinant Bifidobacterium, the binding inhibition of PD-1/PD-L1 interaction and elevated IFN gamma production in mixed lymphocyte culture by anti-human PD-1 scFv secreted from recombinant Bifidobacterium.

Anti-murine PD-1 scFv producing Bifidobacterium as surrogate systemically administered to the syngeneic mice model demonstrated significant tumor growth inhibition. Of particular interest, the suppression of tumor growth was observed in a larger fraction of the treated mice while the control anti-PD-1 antibody showed the effect on only a few mice. The analysis of tumor infiltrating lymphocytes and myeloid cells will be presented as well. Taken together, i-DPS for anti-PD-1 antibody provides a new promising immune-therapeutic modality to target hypoxic solid tumors and also provides a unique insight for antibody drug delivery in cancer immunotherapy.

Citation Format: Koichiro Shioya, Li Wang, Tomio Matsumura, Hitomi Shimizu, Yasuyoshi Kanari, Yuji Seki, Yuko Shimatani, Shun’ichiro Taniguchi, Shiro Kataoka. Anti-PD-1 antibody scFv producing recombinant Bifidobacterium exerts antitumor effect in a larger fraction of the treated mice compared to full-length anti-PD-1 antibody [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A23.