A tumor-targeted cytokine/antibody fusion protein to stimulate anti-cancer immunity

Abstract Interleukin-2 (IL-2) is a pleiotropic cytokine that has clinical utility in stimulating anti-cancer immunity. However, the clinical efficacy of IL-2 is limited by its short serum half-life, systemic toxicity, and concurrent activation of immunostimulatory natural killer (NK) and effector T (Teff) cells and immunosuppressive regulatory T (Treg) cells. IL-2 can signal down an intermediate-affinity receptor consisting of IL-2 receptor beta (IL-2Rβ) and common gamma chain (γc) or a high-affinity receptor that also includes IL-2Rα. Tregs express high levels of IL-2Rα, making them much more responsive to IL-2 than naïve NK and Teff cells. To extend the serum half-life and selectively bias the immunostimulatory functions of IL-2 in a stable unimolecular format, we created a single-chain fusion protein, denoted F10 immunocytokine (F10 IC), that intramolecularly fuses human IL-2 to an anti-IL-2 antibody that sterically blocks the IL-2/IL-2Rα interaction and allosterically enhances the IL-2/IL-2Rβ interaction. To exploit the abundance and accessibility of collagen in the tumor microenvironment for targeting, we fused collagen binding domains to F10 IC in various topographies. These novel fusion proteins occlude IL-2Rα binding and enhance IL-2Rβ binding, thereby eliminating the Treg advantage conferred by IL-2Rα and preferentially activating immune effector cells. Furthermore, these proteins selectively bind purified collagen and are capable of homing to, and being retained in, the tumor in vivo. Building on these promising results, we are assessing the in vivo therapeutic efficacy of these fusion proteins in various murine tumor models to illustrate the potential of collagen binding F10 IC as a powerful anti-cancer therapeutic. Supported by a Sanofi Innovation Award and NIH grants (R01 EB029341, T32 AI007417)