Development and applications of chimera platforms for tyrosine phosphorylation

Chimeric small molecules that induce post-translational modification (PTM) on a target protein by bringing it in proximity to a PTM-inducing enzyme are furnishing novel modalities to perturb protein function. Despite recent advances, such molecules are unavailable for a critical PTM, tyrosine phosphorylation. Furthermore, the contemporary design paradigm of chimeric molecules, formed by joining a non-inhibitory binder of the PTM-inducing enzyme with the binder of the target protein, prohibits the recruitment of most PTM-inducing enzymes as their non-inhibitory binders are unavailable. Here, we report two platforms to generate phosphorylation-inducing chimeric small molecules (PHICS) for tyrosine phosphorylation. We generate PHICS from both non-inhibitory binders (scantily available, platform 1) and kinase inhibitors (abundantly available, platform 2) using cysteine-based group transfer chemistry. PHICS triggered phosphorylation on tyrosine residues in diverse sequence contexts and target proteins (e.g., membrane-associated, cytosolic) and displayed multiple bioactivities, including initiation of a growth receptor signaling cascade and death of drug-resistant cancer cells. These studies provide an approach to induce biologically relevant PTM and lay the foundation for pharmacologic PTM editing (i.e., induction or removal) on target proteins using abundantly available inhibitors of PTM-inducing or erasing enzymes. ### Competing Interest Statement Broad Institute has filed patent applications for the work described herein, some of which were licensed to Photys Therapeutics. A.C. is the scientific founder and is on the scientific advisory board of Photys Therapeutics.