Enhancement of epidermal growth factor receptor antibody tumor immunotherapy by glutaminyl cyclase inhibition to interfere with CD47/signal regulatory protein alpha interactions

Abstract

Integrin associated protein (CD47) is an important target in immunotherapy, as it is expressed as a “don't eat me” signal on many tumor cells. Interference with its counter molecule signal regulatory protein alpha (SIRPα), expressed on myeloid cells, can be achieved with blocking Abs, but also by inhibiting the enzyme glutaminyl cyclase (QC) with small molecules. Glutaminyl cyclase inhibition reduces N‐terminal pyro‐glutamate formation of CD47 at the SIRPα binding site. Here, we investigated the impact of QC inhibition on myeloid effector cell‐mediated tumor cell killing by epidermal growth factor receptor (EGFR) Abs and the influence of Ab isotypes. SEN177 is a QC inhibitor and did not interfere with EGFR Ab‐mediated direct growth inhibition, complement‐dependent cytotoxicity, or Ab‐dependent cell‐mediated cytotoxicity (ADCC) by mononuclear cells. However, binding of a human soluble SIRPα‐Fc fusion protein to SEN177 treated cancer cells was significantly reduced in a dose‐dependent manner, suggesting that pyro‐glutamate formation of CD47 was affected. Glutaminyl cyclase inhibition in tumor cells translated into enhanced Ab‐dependent cellular phagocytosis by macrophages and enhanced ADCC by polymorphonuclear neutrophilic granulocytes. Polymorphonuclear neutrophilic granulocyte‐mediated ADCC was significantly more effective with EGFR Abs of human IgG2 or IgA2 isotypes than with IgG1 Abs, proposing that the selection of Ab isotypes could critically affect the efficacy of Ab therapy in the presence of QC inhibition. Importantly, QC inhibition also enhanced the therapeutic efficacy of EGFR Abs in vivo. Together, these results suggest a novel approach to specifically enhance myeloid effector cell‐mediated efficacy of EGFR Abs by orally applicable small molecule QC inhibitors.

Targeting the CD47-SIRPα Innate Immune Checkpoint to Potentiate Antibody Therapy in Cancer by Neutrophils

“…Neutrophil-mediated ADCC of cetuximab-treated A431 cells or trastuzumab-treated Ba/F3 cells was significantly enhanced by treatment with SEN177 or knockout of QPCTL as well. These results were confirmed by other studies, showing that SEN177 treatment significantly enhanced ADCP by macrophages and neutrophil-mediated ADCC [ 232 , 233 , 234 ]. Another QPCTL inhibitor, luteolin, also abrogated the interaction between CD47 and SIRPα [ 235 ].…”

Targeting Myeloid Checkpoint Molecules in Combination With Antibody Therapy: A Novel Anti-Cancer Strategy With IgA Antibodies?

“…SEN177, a QPCTL inhibitor, or QPCTL knockout abolished the binding of an anti-CD47 antibody (CC2C6) that recognizes the same recognition site as SIRPα ( 83 ). Pre-treatment of MDA-MB-468 and A431 cells with SEN177 for three days, decreased SIRPα-Fc binding dose dependently and enhanced antibody-dependent macrophage-mediated ADCP and neutrophil-mediated ADCC ( 84 ). Traditional CD47 antibodies also bind to CD47 on healthy cells, leading to a decrease in the antibody’s bioavailability, also known as the antigen sink issue.…”

Myeloid checkpoint blockade improves killing of T-acute lymphoblastic leukemia cells by an IgA2 variant of daratumumab

“…QPCTL catalyzes the formation of pyro-glutamate, an amino acid derivative localized at the N-terminus of CD47, crucially involved in binding to SIRPα on myeloid cells ( 14 , 15 ). Inhibition of glutaminyl cyclases in tumor cells by small molecules has been shown to inhibit binding of soluble SIRPα-Fc fusion proteins and to enhance myeloid cell activation against tumor cells ( 15 – 17 ). Antibody isotype switching from human IgG1 to IgA2 can further improve myeloid cell activation, in particular when neutrophils contribute to antibody efficacy ( 18 ).…”