Abstract 2731: CCR5-001, a novel drug Fc-conjugate (DFC) targeting CCR5, demonstrates potent efficacy in a colorectal cancer mouse model

Abstract

Abstract Background The approval of immune checkpoint inhibitors (ICI) such as PD-(L)1 inhibitors has revolutionized cancer therapy and established a role for immune effector cells, most notably CD8+ T cells, in tumor control and destruction. While anti-PD-(L)1 therapy has demonstrated durable responses, only a small subset of patients benefit and respond to therapy. CCR5 is expressed on multiple immune cells (e.g. myeloid-derived suppressor cells) and CCR5-dependent migration of these cells contribute to an immune-suppressive tumor microenvironment (TME) thereby limiting response to ICI therapy. In addition, expression of CCR5 on cancer cells has been linked to increased metastasis and resistance to ICI therapy. Upregulation of CCL5/CCR5 has been associated with poor outcomes in multiple solid tumor indications, including colorectal cancer (CRC). Therefore, targeting CCR5 has the potential to increase response rates to ICI therapy and improve outcomes. Herein, we describe a first-in-class CCR5 targeting DFC, CCR5-001, a multivalent conjugate of a potent, small molecule CCR5 antagonist conjugated to an immune-silent proprietary human IgG1 Fc. This CCR5 targeting DFC has the potential to improve responses to ICI therapy by preventing pro-tumorigenic reprogramming of the TME induced by CCL5/CCR5 expressing tumor and myeloid cells. Methods Binding of CCR5-001 to hCCR5 was measured by surface plasmon resonance (SPR) and to CCR5+ PathHunter cells (DiscoverX) by flow cytometry. Functional activity was determined in CCR5+ PathHunter β-arrestin assay with CCL3 to induce CCR5 signaling according to manufacturer’s instructions. Efficacy was determined in an immune-competent syngeneic mouse model using the CRC cell line, MC38. CCR5-001 was dosed at 20 mg/kg twice per week for two weeks. Tumor volumes were recorded and statistical analysis was conducted by t-test (Mann-Whitney) or two-way ANOVA in Prism. Results CCR5-001 displayed a KD of 4.2 nM to immobilized hCCR5 by SPR and IC50 of 0.63-0.98 nM for binding to engineered CCR5+ PathHunter cells. This high affinity binding translated to potent functional inhibition of CCL3-induced CCR5 signaling with an IC50 of 12.7 nM in CCR5+ cell-based assay. CCR5-001 demonstrated potent, statistically significant (p = 0.0052) tumor growth inhibition of 76% by day 13 in a syngeneic mouse model. Conclusions CCR5-001 demonstrated potent CCR5 binding and functional inhibition of CCR5 signaling in cell-based assays. The in vitro activity translated to robust efficacy as a monotherapy in a syngeneic mouse model. Based on these results and other emerging data, CCR5-001 represents an exciting new avenue for targeting CCR5 with DFCs in solid cancers where the pathology is driven by the CCR5/CCL5 axis. Citation Format: Simon Döhrmann, James Levin, Nicholas Dedeic, Amanda Almaguer, Doug Zuill, Elizabeth Abelovski, Jeffrey B. Locke, Joanne Fortier, Maria Hernandez, Qiping Zhao, Karin Amundson, Madison Moniz, Hongyuan Chen, Dhanya Panickar, Thanh Lam, Grayson Hough, Thomas P. Brady, Allen Borchardt, Jason N. Cole, Leslie W. Tari. CCR5-001, a novel drug Fc-conjugate (DFC) targeting CCR5, demonstrates potent efficacy in a colorectal cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2731.