Abstract 2899: Targeting regulatory T cells with HFB101110, a novel anti-human CCR8 antibody for the treatment of solid tumors

Regulatory T cells (Tregs) contribute to immunosuppression within the tumor microenvironment and have been associated with poor outcomes in a range of cancers. Targeted depletion of tumor-infiltrating Tregs (TITRs) is an attractive therapeutic strategy with the potential to enhance antitumor immunity in patients who do not respond to current treatments. However, such approaches have been limited to date by a lack of markers that are highly specific for TITRs. CCR8 is a chemokine G protein-coupled receptor (GPCR) that has recently been shown to be specifically expressed on TITRs as compared to Tregs in the periphery or other T cells within tumors. Here, we report the development and characterization of HFB101110, a humanized monoclonal antibody against CCR8 with potent and specific antibody-dependent cellular cytotoxicity (ADCC) activity. HFB101110 specifically recognizes an epitope on the N-terminus extracellular domain of CCR8 and does not recognize the closely related chemokine receptor CCR4. HFB101110 acts through a dual mechanism of action, by both depleting CCR8+ cells via ADCC and blocking binding of the CCL1 chemokine to its receptor CCR8. Blockade by HFB101110 inhibited calcium flux and chemotaxis induced by the interaction between CCL1 and CCR8. Furthermore, HFB101110 showed potent single agent anti-tumor activity associated with depletion of intratumoral Tregs in a human CCR8 knock-in mouse model. HFB101110 mediated specific ex vivo killing of Tregs from primary patient tumor samples both in the presence, and in some cases the absence, of allogeneic NK cells. HFB101110 showed favorable pharmacokinetic properties and a favorable developability profile, and was well-tolerated in both wild-type mice and cynomolgus monkeys. HFB101110 is currently being developed as a novel immunotherapy for the treatment of solid tumors coupled with a patient biomarker strategy derived from HiFiBiO’s Drug Intelligent Science (DIS™) single-cell immune profiling platform.

Citation Format: Roshan M. Kumar, Julie Prigent, Hombline Poullain, Ayrin Kok, Carine George, Sami Ellouze, Yun-Yueh Lu, Rebecca Silver, Clarisse Monchecourt, Ross B. Fulton, Qian Zhang, Nicola Beltraminelli, Bernhard Moser, Francisco Adrian, Liang Schweizer. Targeting regulatory T cells with HFB101110, a novel anti-human CCR8 antibody for the treatment of solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2899.

Abstract 1843: Dicovery and characterization of a novel anti-human CXCR5 antibody for the treatment of B cell lymphomas

CXCR5 is a seven transmembrane protein coupled to protein G(i) expressed mainly on mature, resting B cells, follicular helper T cells (TFH), tonsillar B cells, and B cell lymphoma cells. CXCR5 is activated by its ligand CXCL13 and involved in cell migration. Dysregulated CXCL13 and/or CXCR5 expression and signaling have been associated with cancer promotion, as well as autoimmune and chronic inflammatory disorders. Overexpression of CXCL13 in autoimmune and lymphoproliferative disorders has been shown to correlate with disease progression. We therefore hypothesized that an antibody that selectively depletes CXCR5+ malignant B cells through antibody dependent cell-mediated cytotoxicity (ADCC) could be developed to treat B cell lymphomas. Here, we present preclinical data supporting the rationale for indication selection, biomarker identification, dose selection, and phase I clinical trial design. Using our single-cell screening platform technology, CelliGo™, we identified a panel of monoclonal antibodies against human CXCR5. We selected HFB2-4, which binds to CXCR5 expressing cells, blocks CXCL13-induced intracellular signaling and B cell migration, and induces ADCC of Raji B cell lymphoma cells at sub-nM concentrations. HFB2-4 demonstrates good PK behavior in mice and exhibits potent anti-tumor activity in a Raji xenograft murine model. HFB2-4 efficacy in this model is comparable to that of rituximab, despite a lower number of huCXCR5 receptors compared to CD20 on the surface of Raji cells. Our data shows that HFB2-4 holds promise as a therapeutic agent for B cell lymphoproliferative diseases by depleting CXCR5+ tumor B cells in refractory B cell lymphoma and lymphomas derived from severe Sjogren syndrome. Compared to the emerging treatments for refractory B cell lymphomas such as Antibody-Drug-Conjugates, bi-specific antibodies or cell therapies, HFB2-4 may represent a well-tolerated, efficacious, cost-efficient and easy to manufacture alternative.

Citation Format: Ayrin Kok, Germain Margallducos, Stephanie Beq, Clarisse Monchecourt, Hombline Poullain, Muriel David, Carine George, Sami Ellouze, Mingjie Chen, Yun-Yueh Lu, Juying Li, Qian Zhang, Jean Wang, Francisco Adrian, Liang Schweizer, Nicola Beltraminelli. Dicovery and characterization of a novel anti-human CXCR5 antibody for the treatment of B cell lymphomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1843.

Protein arginine methyltransferase 5: A novel therapeutic target for triple-negative breast cancers

TNBC is a highly heterogeneous and aggressive breast cancer subtype associated with high relapse rates, and for which no targeted therapy yet exists. Protein arginine methyltransferase 5 (PRMT5), an enzyme which catalyzes the methylation of arginines on histone and non‐histone proteins, has recently emerged as a putative target for cancer therapy. Potent and specific PRMT5 inhibitors have been developed, but the therapeutic efficacy of PRMT5 targeting in TNBC has not yet been demonstrated. Here, we examine the expression of PRMT5 in a human breast cancer cohort obtained from the Institut Curie, and evaluate the therapeutic potential of pharmacological inhibition of PRMT5 in TNBC. We find that PRMT5 mRNA and protein are expressed at comparable levels in TNBC, luminal breast tumors, and healthy mammary tissues. However, immunohistochemistry analyses reveal that PRMT5 is differentially localized in TNBC compared to other breast cancer subtypes and to normal breast tissues. PRMT5 is heterogeneously expressed in TNBC and high PRMT5 expression correlates with poor prognosis within this breast cancer subtype. Using the small‐molecule inhibitor EPZ015666, we show that PRMT5 inhibition impairs cell proliferation in a subset of TNBC cell lines. PRMT5 inhibition triggers apoptosis, regulates cell cycle progression and decreases mammosphere formation. Furthermore, EPZ015666 administration to a patient‐derived xenograft model of TNBC significantly deters tumor progression. Finally, we reveal potentiation between EGFR and PRMT5 targeting, suggestive of a beneficial combination therapy. Our findings highlight a distinctive subcellular localization of PRMT5 in TNBC, and uphold PRMT5 targeting, alone or in combination, as a relevant treatment strategy for a subset of TNBC.