Mab Designs publishes selective IL-6 trans-signalling inhibitor C20 data
Mab Designs has announced the publication of preclinical data on C20, its anti-IL-6 receptor antibody, in Communications Biology, a Nature Portfolio journal. The paper, produced in collaboration with Otto von Guericke University Magdeburg, reports that C20 selectively inhibits IL-6 trans-signalling without disrupting the classic IL-6 signalling pathway, a distinction that has eluded every antibody so far approved in the class.
The study used epitope mapping to localise a conformational epitope on domain D2 of human IL-6R, away from the IL-6 binding site itself. The authors conclude that C20 most likely blocks binding site IIIb, the interface between IL-6R and gp130. That contact appears to be required for trans-signalling but dispensable for classic signalling, suggesting the two modes of IL-6 action assemble structurally distinct receptor complexes in humans.
How C20's selectivity works
The mechanistic finding has implications beyond this candidate. C20 binds both the soluble (shed) receptor and the membrane-bound receptor with comparable, picomolar affinity, yet functional inhibition is confined to the trans-signalling arm. Mab Designs co-founder and managing director Andrew Clark described this as selectivity exercised at the level of receptor complex assembly rather than target recognition, calling it "not a binding property."
In practical terms, C20 carries an IC50 of 3.5 nM as an IgG1 and 3.2 nM as a Fab. In human liver cells the Fab form left the acute-phase response intact, consistent with classic signalling remaining active. In endothelial cells, C20 abolished trans-signalling-driven expression of CCL2 and VEGF and returned tube formation to baseline. The antibody has no measurable effect on IL-11 signalling; because it targets IL-6R rather than gp130, the subunit shared across the broader IL-6 cytokine family, selectivity for IL-6 is intrinsic to the design.
Market context and competitive positioning
The IL-6 pathway has been commercially validated for more than twenty years. Approved antibodies in the class, including tocilizumab (Roche/Chugai) and sarilumab (Sanofi/Regeneron), target either IL-6 itself or IL-6R but block both signalling modes simultaneously. Suppressing classic signalling is associated with elevated infection risk and blunted host defence, a side-effect profile that constrains use in some patient populations.
Trans-signalling selective inhibition has been a research ambition in the field for a number of years. Academics have previously used a fusion protein tool compound, sgp130Fc, to separate the two pathways in animal models, but a selective clinical-grade antibody has not previously been described in peer-reviewed literature. If C20's preclinical profile translates, it could offer a differentiated safety argument in inflammatory indications where the approved agents carry restrictions, including rheumatoid arthritis, inflammatory bowel disease, and cytokine release syndrome contexts.
Mab Designs is a privately held London company with no disclosed development partner for C20 as yet, and the compound appears to be at an early stage with no IND or clinical filing mentioned. The study was conducted under an institutional research agreement; Mab Designs had no role in study design, data collection, or publication decisions, which strengthens the independence of the reported results. The paper is open access via the DOI provided in the release, and the next milestones investors and potential partners will watch for are in vivo disease model data and any indication of a formal development programme.