Improving IL-12 therapeutic window: New FairJourney Bio study
FairJourney Bio has announced the publication of a peer-reviewed study in mAbs describing a novel approach with the potential to improve the therapeutic window of IL-12, a potent anti-tumor cytokine.
FJBio delivered the end-to-end antibody discovery and engineering campaign for the venture-backed oncology program across its sites in Porto, Portugal, and Cambridge, UK.
IL-12, while one of the most potent anti-tumor cytokines, currently has limited development due to severe immune-related systemic toxicity. Previous strategies to improve its therapeutic window, including intratumoral dosing, half-life extension and protease-cleavable pro-drugs, have had limited clinical success.
The paper, ‘Conditional activation of IL-12 through a Fibronectin-EDB dependent switch gate’, reports the generation of a dual-specificity antigen-binding fragment (Fab) engineered to bind competitively to IL-12 and fibronectin-EDB (FN-EDB), a tumor-associated matrix antigen. This reversible switch is designed to mask IL-12 until it encounters FN-EDB, enabling its conditional activation in the tumor microenvironment.
The study describes what the authors report as the first demonstration of a reversible trans-activation logic gate for tumor-conditional cytokine delivery. In vitro data demonstrates FN-EDB-dependent IL-12 availability and activity, while quantitative systems pharmacology (QSP) modeling predicts a substantially improved therapeutic window for the approach.
The novel format combines a dual-specificity switch arm with a separate, higher-affinity FN-EDB targeting arm. QSP modeling was used to define the binding parameters required for the switch to function before a candidate existed. Working to this predefined affinity window, FJBio introduced IL-12 binding into existing FN-EDB binders using targeted mutagenesis, before optimizing both specificities through a two-stage combinatorial engineering campaign. The resulting affinities were then tuned against one another, enabling the switch arm to bind competitively to IL-12 or FN-EDB, while the targeting arm supports avidity-driven localization to the tumor and conditional activation of IL-12.
