Leveraging Covalency to Stabilize Ternary Complex Formation For Cell-Cell "Induced Proximity"

Area of Science:

• Translational chemical biology
• Synthetic modalities
• Event-driven pharmacology

Background:

• Heterobifunctional molecules like PROTACs and ARMs induce targeted protein degradation or immune clearance via reversible ternary complexes.
• Key parameters for efficacy include affinity, residence time, and turnover, which are often limited by destabilizing forces in induced proximity systems.
• Covalent approaches, such as Covalent Immune Recruiters (CIRs), have been developed to kinetically stabilize these complexes.

Purpose of the Study:

• To address challenges in inducing cell-cell proximity using the CIR strategy in antibody recruitment and engineered T cell models.
• To investigate the mechanism and functional enhancements of covalent chimeras compared to non-covalent analogs.

Main Methods:

• Applied the CIR strategy to convert Antibody Recruiting Molecules (ARMs) into covalent chimeras for irreversible antibody recruitment to tumor cells.
• Utilized electrophile preorganization and kinetic effective molarity for selective covalent engagement of serum antibodies.
• Investigated analogous CIR modalities with peptidic/carbohydrate ligands and SuFEx electrophiles, and studied T cells engineered with specific receptors.

Main Results:

• Covalent chimeras demonstrated significant functional enhancements over non-covalent ARMs in immune assays.
• Enhanced efficacy was attributed to increased kinetic stability of ternary complexes, not just concentration.
• Covalent receptor engagement in T cells uniquely enforced downstream activation signaling compared to non-covalent interactions.

Conclusions:

• Covalent Immune Recruiters (CIRs) offer a strategy to overcome destabilizing forces and enhance the kinetic stability of induced proximity complexes.
• Covalent engagement, beyond cysteine residues, provides a robust mechanism for improved therapeutic outcomes in cell-cell proximity applications.
• Further optimization of covalent chimeric/bifunctional molecules holds promise for diverse cell-cell proximity-based therapeutic applications.