Monocyte Covalent Immune Recruiters: Tools to Modulate Synthetic Immune Recognition

Abstract

Immune recruiters are small molecule immunotherapeutics which redirect endogenous components of the immune system to target cells to elicit anti-cancer responses. Current immune recruiters made in the Rullo Lab are heterobispecific molecules which bind receptors on cancer cells and ligand-specific antibodies. Upon antibody binding, a proximity-induced covalent reaction with nearby nucleophilic residues installs a targeting ligand onto the protein. The resultant antibody conjugate then facilitates cancer killing through immune cell recruitment. Covalency circumvents limited binding affinity of the ligand•antibody complex, however antibody•immune receptor affinity remains an issue. This thesis presents an alternative immune recruiting strategy through direct engagement of effector immune cells; monocyte covalent immune recruiters (mCIRs). mCIRs utilize a monocyte specific peptide (cp33) to bind CD64, an activating receptor on monocytes. By incorporating a sulfonyl fluoride electrophile onto the N-terminus of cp33, selective covalent labelling of CD64 was achieved within 24 h. Furthermore, mCIRs demonstrated enhanced monocyte function relative to antibody recruiting platforms. However, these constructs have demonstrated that the order of addition to the target receptor then to CD64 is critical for bridging the two species. As a result, the effect of covalency on complex simplification and monocyte function has yet to be determined. Despite this, mCIRs represent a covalent immune recruitment strategy with the potential to address shortcomings of antibody-based therapeutics.