Direct and indirect immune effects of CMP-001, a virus-like particle containing a TLR9 agonist

Abstract

BackgroundCMP-001, also known as vidutolimod, is a virus-like particle containing a TLR9 agonist that is showing promise in early clinical trials. Our group previously demonstrated that the immunostimulatory effects of CMP-001 are dependent on an anti-Qβ antibody response which results in opsonization of CMP-001 and uptake by plasmacytoid dendritic cells (pDCs) that then produce interferon (IFN)-α. IFN-α then leads to an antitumor T-cell response that is responsible for the in vivo efficacy of CMP-001. Here, we explore mechanisms by which the initial effects of CMP-001 on pDCs activate other cells that can contribute to development of an antitumor T-cell response.MethodsUptake of CMP-001 by various peripheral blood mononuclear cell (PBMC) populations and response to anti-Qβ-coated CMP-001 were evaluated by flow cytometry and single-cell RNA sequencing. Purified monocytes were treated with anti-Qβ-coated CMP-001 or recombinant IFN-α to evaluate direct and secondary effects of anti-Qβ-coated CMP-001 on monocytes.ResultsMonocytes had the highest per cell uptake of anti-Qβ-coated CMP-001 with lower levels of uptake by pDCs and other cell types. Treatment of PBMCs with anti-Qβ-coated CMP-001 induced upregulation of IFN-responsive genes including CXCL10, PDL1, and indoleamine-2,3-dioxygenase (IDO) expression by monocytes. Most of the impact of anti-Qβ-coated CMP-001 on monocytes was indirect and mediated by IFN-α, but uptake of anti-Qβ-coated CMP-001 altered the monocytic response to IFN-α and resulted in enhanced expression of PDL1, IDO, and CD80 and suppressed expression of CXCL10. These changes included an enhanced ability to induce autologous CD4 T-cell proliferation.ConclusionsAnti-Qβ-coated CMP-001 induces IFN-α production by pDCs which has secondary effects on a variety of cells including monocytes. Uptake of anti-Qβ-coated CMP-001 by monocytes alters their response to IFN-α, resulting in enhanced expression of PDL1, IDO and CD80 and suppressed expression of CXCL10. Despite aspects of an immunosuppressive phenotype, these monocytes demonstrated increased ability to augment autologous CD4 T-cell proliferation. These findings shed light on the complexity of the mechanism of action of anti-Qβ-coated CMP-001 and provide insight into pathways that may be targeted to further enhance the efficacy of this novel approach to immunotherapy.

Monocytes Exposed to Immune Complexes Reduce pDC Type 1 Interferon Response to Vidutolimod

“…Figure 7 A involved addition of soluble anti-Qβ to a sample containing a set amount of vidutolimod allowing for development of immune complex in the sample while Figure 7 B involved addition of varying amounts of immune complex itself. We previously reported that uptake of antibody-coated vidutolimod by monocytes is significantly higher than that of pDCs even though pDC uptake is responsible for the resulting production of Type I Interferon [ 3 ]. There is likely competition for uptake of vidutolimod in the experiments illustrated in Figure 7 A between monocytes and pDCs that impacts on TLR9 agonist activation of pDCs.…”

“…This uptake leads to robust production of Type 1 Interferon by pDCs. Monocytes phagocytose more anti-Qβ-coated vidutolimod particles on a per cell basis than do pDCs which, in the context of a Type 1 Interferon inflammatory milieu, enhances their ability to induce T cell proliferation [ 3 ]. The result of these changes is generation of a T-cell dependent anti-tumor immune response [ 2 ].…”

“…Antibody-coated vidutolimod induced robust production of Type 1 Interferon by pDCs that, in turn, induced changes in multiple cell types. These additional changes included enhancing the ability of monocytes to induce CD4 T cell proliferation [2,3]. We recently reported promising results from a clinical trial of vidutolimod plus anti-PD1 therapy in patients with melanoma demonstrating the potential clinical relevance of these findings [4].…”

In situ vaccination using unique TLR9 ligand K3-SPG induces long-lasting systemic immune response and synergizes with systemic and local immunotherapy

“…A/D- and P-type CpG ODNs are potent type I IFN inducers, because the higher structure formed by base paring between their palindromic sequences causes their localization to early endosome that is prerequisites for robust type I IFN induction 9 – 11 . A general challenge for their clinical application is that their higher structure results in aggregation, while CpG-A ODN designated as CMP-001 that is packaged in a virus-like particle has been developed and tested in clinical trials 12 , 13 . B/K- and C-type CpG ODNs are also applied for clinical use, and among them, the B/K type has been the most extensively studied 9 , 14 , 15 .…”

In situ delivery of nanoparticles formulated with micron-sized crystals protects from murine melanoma

“…The patient experienced regression of all treated cutaneous lesions, in addition to 50% regression of distant metastases. 6 Some recent examples of intratumoral treatment in melanoma includes CMP-001, a bacteriophage virus-like particle (VLP) loaded with A-type CpGs (NCT02680184/NCT03084640, formerly called QßG10 7 ) without any tumor antigens. This therapy is currently being examined in combination with systemic anti-programmed cell death protein-1(PD-1) in several clinical trials for patients with advanced melanoma with previous resistance to anti-PD-1 treatment.…”