An optimized IL-12-Fc expands its therapeutic window, achieving strong activity against mouse tumors at tolerable drug doses

Interleukin-12 (IL-12) has emerged as one of the most potent cytokines for tumor immunotherapy due to its ability to induce interferon γ (IFNγ) and polarize Th1 responses. Clinical use of IL-12 has been limited by a short half-life and narrow therapeutic index. We generated a monovalent, half-life-extended IL-12-Fc fusion protein, mDF6006, engineered to retain the high potency of native IL-12 while significantly expanding its therapeutic window. In vitro and in vivo activity of mDF6006 was tested against murine tumors. To translate our findings, we developed a fully human version of IL-12-Fc, designated DF6002, which we characterized in vitro on human cells and in vivo in cynomolgus monkeys in preparation for clinical trials. The extended half-life of mDF6006 modified the pharmacodynamic profile of IL-12 to one that was better tolerated systemically while vastly amplifying its efficacy. Mechanistically, mDF6006 led to greater and more sustained IFNγ production than recombinant IL-12 without inducing high, toxic peak serum concentrations of IFNγ. We showed that mDF6006’s expanded therapeutic window allowed for potent anti-tumor activity as single agent against large immune checkpoint blockade-resistant tumors. Furthermore, the favorable benefit-risk profile of mDF6006 enabled effective combination with PD-1 blockade. Fully human DF6002, similarly, demonstrated an extended half-life and a protracted IFNγ profile in non-human primates. An optimized IL-12-Fc fusion protein increased the therapeutic window of IL-12, enhancing anti-tumor activity without concomitantly increasing toxicity. This research was funded by Dragonfly Therapeutics. [Display omitted] •Recombinant IL-12 in cancer therapy is limited by a narrow therapeutic index•Extending IL-12’s half-life results in a sustained IFNγ response after a single dose•Systemic IL-12-Fc can be dosed safely and induces strong anti-tumor responses•DF6002 is an IL-12-Fc being tested in the clinic for solid cancer treatment IL-12 has great potential for cancer treatment due to its potent ability to stimulate both adaptive and innate anti-tumor immune responses. However, because of its short half-life, recombinant IL-12 necessitated frequent dosing, which led to high-amplitude IFNγ responses and ultimately dose-limiting toxicities in the clinic. Dragonfly Therapeutics has developed an engineered IL-12 therapy that is well tolerated when administered systemically and results in potent anti-tumor responses as monotherapy