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

Background: Interleukin- 12 (IL-12) has emerged as one of the most potent cytokines for tumor immunotherapy due to its ability to induce interferon gamma (IFN gamma) and polarize Th1 responses. Clinical use of IL-12 has been limited by a short half-life and narrow therapeutic index. Methods: 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. Findings: 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 IFNg production than recombinant IL-12 without inducing high, toxic peak serum concentrations of IFNg. 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 IFNg profile in non-human primates. Conclusion: An optimized IL-12-Fc fusion protein increased the therapeutic window of IL-12, enhancing anti-tumor activity without concomitantly increasing toxicity.