Design and Structural Requirements of the Potent and Safe TLR-9 Agonistic Immunomodulator MGN1703

Abstract

Single-stranded oligodeoxynucleotides (ODN), containing nonmethylated cytosine–guanine motifs (CpG ODN), are recognized by the innate immune system as “danger signals.” CpG ODN are efficacious immunomodulators but require phosphorothioate (PT) or other backbone modifications for metabolic stability, which cause toxicities in mice and primates. We therefore designed a covalently closed DNA molecule (dSLIM®) where two single-stranded loops containing CG motifs are connected through a double-stranded stem in the absence of any nonnatural DNA component. The most promising immunomodulator, MGN1703, comprises two loops of 30 nucleotides containing three CG motifs each, and a connecting stem stem of 28 base pairs. MGN1703 stimulates cytokine secretion [interferon (IFN)-α, IFN-γ, interleukin (IL)-12, IL-6, and IL-2] and activates immune cells by increased expression of CD80, CD40, human leukocyte antigen (HLA)-DR and ICAM-1. Efficacy of immunomodulation strictly depends on the descriptive dumbbell shape and size of the molecule. Variations in stem length and loop size lead to reduced potency of the respective members of the dSLIM® class. In a representative mouse model, toxicities from injections of high amounts of a CpG ODN-PT and of MGN1703 were evaluated. The CpG ODN-PT group showed severe organ damage, whereas no such or other pathologies were found in the MGN1703 group. Oncological clinical trials of MGN1703 already confirmed our design.

Natural killer cells in HIV-1 infection and therapy

“…Several studies have shown that TLRs agonists can directly activate NK cells and boost their anti-viral potentials [172–174]. One possible candidate is MGN1703, a novel TLR9 agonist currently under clinical testing for the treatment of metastatic colorectal cancer [175–178]. Indeed, MGN1703 is able to stimulate plasmacytoid DCs to produce IFN-α that, in turn, increase the expression of NKp46 on NK cells and induce the killing of HIV-1 infected T cell targets [22, 60, 174].…”

CpG oligodeoxynucleotide nanomedicines for the prophylaxis or treatment of cancers, infectious diseases, and allergies

“…74,75 CpG ODNs with this structure do not have 75 Induction of these cytokines suggests that MGN1703 has the potential to activate both cellular immunity and humoral immunity. Furthermore, MGN1703 upregulated the expression of human leukocyte antigen D related and intercellular adhesion molecule-1 in B-lineage RPMI-8226 cells.…”

“…In a recent preclinical study, major liver damage and spleen damage were observed in mice administered a CpG-B ODN (ODN1826). 75 Moreover, in the Phase III clinical trial in which a CpG-B ODN (PF-3512676, also known as ODN2006 or CpG-7909) was combined with standard chemotherapy, it was reported that patients administered with the CpG-B ODN had a high probability of developing adverse events. 114,115 The results of these preclinical and clinical studies suggest that CpG ODNs with a phosphodiester backbone would be preferable to those with a phosphorothioate backbone.…”

A Novel Toll-Like Receptor 9 Agonist, MGN1703, Enhances HIV-1 Transcription and NK Cell-Mediated Inhibition of HIV-1-Infected Autologous CD4 + T Cells

“…MGN1703 is a novel, dumbbell-shaped, covalently closed DNA construct, synthesized from nonmodified natural DNA, that we used to agonize TLR9 (7)(8)(9), and we refer to cells activated via this TLR9-triggered pathway as "MGN1703-activated" cells here.…”