Immune checkpoint inhibitors are transforming cancer care, but also cause immune-related adverse events (irAEs). A robust clinical and research framework is critical to developing effective institutional strategies for patient management, defining evidence-based management strategies, and uncovering mechanistic insights into irAEs. Here, we will present insights as we have implemented these systematic approaches, as well as clinical and translational findings gained within this framework. 

Altering the subclass of an otherwise identical monoclonal IgG lineage can significantly impact the half-life, receptor binding affinity, and effector function potential of the antibody. To date however, only a small part of the raw material that occurs naturally as IgG subclass and allotype has been used for engineering therapeutic antibodies. These allelic variants potentially offer a means of finely tuning IgG for a range of clinically desirable properties.

The development of immunotherapy drugs as an effective strategy for combating cancer is an area of intense research with the need for assays for testing biologics and small molecules that modulate immune checkpoint receptors. Here we will highlight easy-to-use, cell-based assays as an effective tool for screening and characterizing candidate therapeutics for clinically relevant inhibitory and co-stimulatory checkpoint receptor targets – SIRPα and PD-1.

Myeloid-derived suppressor cells (MDSC) are immature myeloid cells that dampen antitumor immune responses and promote tumor growth. We characterized the phenotype and function of monocytic MDSCs (M-MDSC) generated by coculture of human PBMCs with cancer cells in vitro. M-MDSCs expressed higher cell surface levels of immunoglobulin-like transcript 3 (ILT3 or LILRB4) compared with monocytes. Therefore, we investigated how ILT3 targeting could modulate M-MDSC cell function. Treatment with an anti-ILT3 antibody impaired the acquisition of the M-MDSC suppressor phenotype and reduced the capacity of M-MDSCs to cause T cell suppression. Thus, antagonism of ILT3 may enhance the efficacy of immune checkpoint inhibitors.

LILRB family of receptors transduce signals via ITIMs that lead to negative regulation of immune cell activation. The activation of LILRBs on immune cells may contribute to cancer immune evasion. Some LILRBs expressed by tumor cells may regulate cancer development. LILRBs thus have dual concordant roles in cancer – as immune checkpoint molecules and as tumor-sustaining factors. LILRBs thus represents a novel class of targets for cancer antibody therapy.

HHLA-2 (B7H7) is a member of the B7 family of ligands and mediates both co-stimulatory (via TMIGD2/CD28H) and inhibitory effects on T cells. Through a HHLA2-Fc receptor screen we identified KIR3DL3 as an inhibitory receptor expressed in T and NK cells. Given the high expression of HHLA2 in PD-L1 negative tumors we developed ligand blocking KIR3DL3 and HHLA2 antibodies and showed checkpoint inhibition in T and NK cells.

With funding from the Biden Cancer Moonshot Program, we have developed novel immunotherapeutic bi-specific proteins and CAR T cells that target two abnormal glycans expressed widely in many diverse solid and liquid cancers, termed “Glycan-dependent T cell Recruiter” or GlyTR (pronounced ‘glitter’). GlyTR therapeutics bind with high specificity to their glycan targets, robustly activate T cells only in the presence of cancer cells, induce T cell dependent killing of many diverse cancer cells (EC50 ~1pM) without killing healthy lymphocytes or primary epithelial cells, and significantly accumulate in tumor xenografts but not target expressing normal mouse organs to trigger marked tumor killing/regression without inducing “on target, off cancer” major organ toxicity in pre-clinical models.

Sialoglycans have emerged as a critical glyco-immune checkpoint that impairs antitumor response but are undruggable using conventional therapeutic approaches due to their structure heterogeneity and promiscuous ligand-receptor interactions. We have developed an engineered human sialidase-based EAGLE platform to overcome this hurdle by enzymatically cleaving the critical moiety, terminal sialic acids, and off sialoglycans. EAGLEs have demonstrated single-agent activity and a wide safety margin in preclinical models.

Removal of monosaccharides called sialic acids from the surface of either T cells or APCs increases activation of the former. We have discovered the molecular basis for this effect; CD28, the most common co-stimulatory receptor on T cells, is a sialic acid binding protein and ligation of sialic acids prevents CD28 from associating with its activatory proteinaceous ligands CD80/86. Importantly, we show that activation of T cells through removal of sialic acids is synergistic with PD-1 blockade – a result that underscores the importance of sialic acids at the immunological synapse to human health and disease.

Creation of TNF receptor superfamily agonistic and antagonistic antibodies for cancer and autoimmunity is desired. We have focused on TNFR2 as an attractive target for Treg expansion and depletion. Many therapeutic antibodies need involvement of the Fc-receptor for signal strength. It is now possible to create new classes of antibodies independent of Fc receptor binding. Fc-receptors can facilitate cross-linking and signal strength but it also creates in vivo toxicity problems.

Tumors evolve the ability to induce and maintain a microenvironment capable of shielding it from immune surveillance. Macrophage repolarization is capable of shifting the polarity of the tumor microenvironment away from tolerance and toward an immune attack. Given the prevalence of human tumors highly infiltrated with tolerogenic macrophages, targeting them is a potent strategy to broaden the clinical reach of what was possible with T cell checkpoint inhibitors. Verseau is developing a pipeline of potent novel immune modulating antibodies for clinical testing.

An understanding of the native human immune response to cancer has the potential to yield novel therapeutic strategies for cancer. We suggest that anti-tumor immunity can be initiated by tumor specific antibodies derived from select patients, which can be used to promote tumor cell death and an adaptive immune response.   

Cumulative research implicates TANs in immune-suppression and CSCs in immune-evasion. Inhibition of the dual endothelin-1/VEGF-signal peptide receptor (DEspR) using a humanized anti-DEspR IgG4^S228P-antibody, hu6g8, induces apoptosis in DEspR+ neutrophils and CSCs. This mode-of-action differentiates a therapeutic paradigm to block neutrophil/CSC-mediated resistance to immune checkpoint-inhibitors and pro-metastatic functions. Prevalence of DEspR-expression in solid tumors and emerging safety profile of hu6g8 in hyperinflammatory states delineate a rational profile for synergistic therapeutic combinations.