DF6215, an α-optimized IL-2-Fc fusion, expands immune effectors and drives robust preclinical anti-tumor activity.

DF6215 is a rationally engineered interleukin-2 (IL-2) Fc-fusion protein developed to overcome efficacy and safety limitations of traditional IL-2 cancer immunotherapy. Unlike non-alpha (non-α) IL-2 variants that eliminate CD25 binding and underperform clinically, DF6215 retains moderate IL-2 receptor α (IL-2Rα) affinity while enhancing IL-2Rβγ signaling and extending the half-life via an engineered immunoglobulin (Ig)G1 Fc domain. This design preferentially expands cytotoxic CD8+ T cells and natural killer cells over regulatory T cells, resulting in favorable effector-to-regulatory cell ratios, enhanced immune activation, and robust tumor regression in mouse models. In poorly immunogenic tumors, DF6215 synergized with PD-1 blockade to achieve durable responses without added toxicity. Cynomolgus monkey studies confirm DF6215's pharmacodynamics and favorable safety profile, with no signs of vascular leak syndrome or cytokine release syndrome. These findings position DF6215 as a differentiated IL-2 capable of modulating the tumor microenvironment and achieving potent anti-tumor immunity with improved tolerability, supporting its advancement into clinical trials for solid tumors.