Inhibition of LILRB2 by a Novel Blocking Antibody Designed to Reprogram Immunosuppressive Macrophages to Drive T-Cell Activation in Tumors.

Tumor-associated macrophages (TAM) play an important role in maintaining the immunosuppressive state of the tumor microenvironment (TME). High levels of CD163+ TAMs specifically are associated with poor prognosis in many solid tumor types. Targeting TAMs may represent a key approach in development of the next generation of cancer immune therapeutics. Members of the leukocyte immunoglobulin-like receptor B (LILRB) family, including LILRB2 (ILT4), are known to transmit inhibitory signals in macrophages and other myeloid cells. Leveraging bulk and single cell RNA-sequencing datasets, as well as extensive immunophenotyping of human tumors, we found that LILRB2 is highly expressed on CD163+ CD11b+ cells in the TME and that LILRB2 expression correlates with CD163 expression across many tumor types. To target LILRB2, we have developed JTX-8064, a highly potent and selective antagonistic mAb. JTX-8064 blocks LILRB2 binding to its cognate ligands, including classical and nonclassical MHC molecules. In vitro, JTX-8064 drives the polarization of human macrophages and dendritic cells toward an immunostimulatory phenotype. As a result, human macrophages treated with a LILRB2 blocker are reprogrammed to increase the activation of autologous T cells in co-culture systems. Furthermore, JTX-8064 significantly potentiates the activity of anti-PD-1 in allogeneic mixed lymphocyte reaction. In a human tumor explant culture, pharmacodynamic activity of JTX-8064 was observed in monotherapy and in combination with anti-PD-1. Collectively, our work provides strong translational and preclinical rationale to target LILRB2 in cancer.

Differential expression of CCR8 in tumors versus normal tissue allows specific depletion of tumor-infiltrating T regulatory cells by GS-1811, a novel Fc-optimized anti-CCR8 antibody.

The presence of T regulatory (Treg) cells in the tumor microenvironment is associated with poor prognosis and resistance to therapies aimed at reactivating anti-tumor immune responses. Therefore, depletion of tumor-infiltrating Tregs is a potential approach to overcome resistance to immunotherapy. However, identifying Treg-specific targets to drive such selective depletion is challenging. CCR8 has recently emerged as one of these potential targets. Here, we describe GS-1811, a novel therapeutic monoclonal antibody that specifically binds to human CCR8 and is designed to selectively deplete tumor-infiltrating Tregs. We validate previous findings showing restricted expression of CCR8 on tumor Tregs, and precisely quantify CCR8 receptor densities on tumor and normal tissue T cell subsets, demonstrating a window for selective depletion of Tregs in the tumor. Importantly, we show that GS-1811 depleting activity is limited to cells expressing CCR8 at levels comparable to tumor-infiltrating Tregs. Targeting CCR8 in mouse tumor models results in robust anti-tumor efficacy, which is dependent on Treg depleting activity, and synergizes with PD-1 inhibition to promote anti-tumor responses in PD-1 resistant models. Our data support clinical development of GS-1811 to target CCR8 in cancer and drive tumor Treg depletion in order to promote anti-tumor immunity.

Divergent role of donor dendritic cells in rejection versus tolerance of allografts.

Little is known about heart tissue/donor dendritic cells, which play a key role in mounting alloimmune responses. In this report, we focus on three primary features of donor dendritic cells: their generation, their trafficking after transplantation, and their role in regulating tolerance versus rejection. Using transgenic mice as donors of heart allografts enabled us to monitor trafficking of donor dendritic cells after transplantation. Donor dendritic cells rapidly migrated into secondary lymphoid tissues within 3 h of transplantation. We found that the chemokine receptor CX3CR1 regulates the generation of heart tissue dendritic cells constitutively. Compared with wild-type hearts, CX3CR1(-/-) hearts contained fewer dendritic cells, and heart allografts from CX3CR1(-/-) donors survived significantly longer without immunosuppression. Unexpectedly, though, co-stimulatory blockade with anti-CD154 or CTLA4-Ig induced long-term survival for wild-type heart allografts but not for CX3CR1(-/-) heart allografts. Increasing the dendritic cell frequency in CX3CR1(-/-) hearts by treatment with Flt3L restored the anti-CD154-induced prolongation of CX3CR1(-/-) heart allograft survival. Compared with wild-type donors, depleting transgenic donors of dendritic cells before heart transplantation also markedly worsened chronic rejection under anti-CD154 treatment. These data indicate the importance of the CX3CR1 pathway in the generation of heart tissue dendritic cells and the divergent role of tissue/dendritic cells in rejection versus tolerance.