Engineered Switch-IL-12 antibody conditionally activates IL-12 only in presence of tumor antigen Fibronectin-EDB

Potent immune-activators like interleukin-12 (IL-12) hold significant promise for treating solid tumors, particularly in challenging contexts like pancreatic ductal adenocarcinoma (PDAC), which is known for its immunosuppressive tumor microenvironment. However, the clinical application of systemic IL-12 has been severely limited by high systemic toxicity, leading to a narrow therapeutic window. Current delivery platforms, including cellular encapsulation and virotherapy, attempt to localize IL-12 activity, but a more precise, conditional activation mechanism is needed to specifically target tumor sites and minimize off-target effects.

Researchers engineered a novel, reversible antibody format, termed Switch-IL-12, designed for conditional activation of IL-12. This format comprises a switch arm and a targeting arm. The switch arm is a dual-specificity Fab that competitively binds to either tethered IL-12 or the pan-tumor matrix antigen Fibronectin-EDB (FN-EDB). The FN-EDB targeting arm promotes avidity-driven unveiling of IL-12 when FN-EDB is present. A quantitative systems pharmacology (QSP) model was employed to define the necessary binding parameters for Switch-IL-12 activity. A phage screening and rational library design process was used to generate switch binders with the desired binding profiles. In vitro functional data were collected to validate the FN-EDB dependent Switch-IL-12 activity.

The engineered Switch-IL-12 antibody successfully demonstrated conditional activation of IL-12 in the presence of the tumor matrix antigen Fibronectin-EDB (FN-EDB). The QSP model was instrumental in defining the critical binding parameters required for this selective activation.

In vitro functional data unequivocally supported the FN-EDB dependent Switch-IL-12 activity, confirming the design's efficacy in a controlled environment. This conditional activation mechanism ensures that IL-12 is unveiled and becomes active only when FN-EDB is present, thereby localizing its potent immunostimulatory effects. The integration of these in vitro findings back into the QSP model allowed for further refinement and expansion of the predicted therapeutic index for Switch-IL-12, suggesting a path toward improved safety and efficacy compared to systemic IL-12 administration.