Design and Structural Requirements of the Potent and Safe TLR-9 Agonistic Immunomodulator MGN1703.
Bottom Line: 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.The CpG ODN-PT group showed severe organ damage, whereas no such or other pathologies were found in the MGN1703 group.
Affiliation: 1Mologen AG, Berlin, Germany.
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.
No MeSH data available.
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Mentions: Some reports described the requirement of nucleic acid secondary structure or the buildup of higher molecular complexes as a prerequisite of immunological efficacy [48,49]. Therefore, we designed variants of stem-loop constructs differing in number and distribution of CG motifs, stem and loop size, and number of loops and evaluated their modulatory potential. Besides MGN1703, these were a single-loop stem construct (Mod-1), a double-loop stem construct with CG motifs in only one loop (Mod-2), and another double-loop stem construct with CG motifs in its stem (Mod-3) (Fig. 2A). All molecules contained the same immunomodulatory sequence, a stretch of at least 20 nucleotides containing 3 CG motifs. Regarding expression of surface molecules CD80/B7-1 and HLA-DR, a change in structure and number of CG motifs reduced the activation potential compared with MGN1703 (Fig. 2B, C).
No MeSH data available.