Summary
A bioRxiv preprint describes BiAb J31, an IgG-like bispecific antibody that links TNF-α to the endocytic receptor ASGPR1. In HepG2 cell experiments, the antibody recruited TNF-α-containing complexes and promoted their uptake.
Researchers have developed an IgG-like bispecific antibody that directs tumour necrosis factor alpha (TNF-α) towards an endocytic receptor on cells, creating a potential route for removing extracellular cytokine complexes through cellular uptake. In a bioRxiv preprint posted on 16 September 2026, the team reported that the antibody, named BiAb J31, recruited TNF-α to ASGPR1 and promoted uptake in HepG2 cell experiments.
The work is an in-vitro study rather than an animal or clinical investigation. Its central result is a demonstration of antibody-mediated cytokine recruitment and uptake in cultured cells.
Contents
How BiAb J31 is designed
ASGPR1 is an endocytic receptor whose extracellular region can bind engineered molecules and help bring them into cells. The researchers focused on a membrane-proximal part of ASGPR1 rather than its carbohydrate-recognition domain. Their screening work localised J31 recognition to residues 62–100 of ASGPR1.
J31 was first isolated after immunisation with an engineered ASGPR1 extracellular domain, followed by screening against wild-type ASGPR1 and HepG2 cells. The researchers then combined its variable domains with the unmodified variable regions of adalimumab, which provide TNF-α recognition. Knobs-into-holes and CrossMab methods were used to assemble the bispecific antibody, along with the Fc substitutions L234A/L235A/P329G.
The resulting molecule was designed to bind both TNF-α and ASGPR1. In effect, one part of the antibody recognises the cytokine while the other attaches the cytokine-containing complex to a cell-surface receptor capable of endocytic uptake.
Evidence of TNF-α recruitment and uptake
Binding and bridging assays showed that BiAb J31 retained binding to HepG2 cells and engaged both of its target antigens. Sequential binding experiments then demonstrated recruitment of TNF-α to cells treated with the bispecific antibody.
Live-cell imaging provided a second line of evidence. Fluorescent antibody-containing complexes were seen entering cells and overlapping with LysoTracker-positive compartments, which are acidic intracellular compartments associated with the endocytic and lysosomal pathway.
The researchers also measured fluorescent signal in the surrounding culture medium. In HepG2 cultures containing BiAb J31, TNF-α and a phycoerythrin-conjugated detection antibody, supernatant PE fluorescence fell by approximately 60% over 90 minutes. In the context of the binding and imaging experiments, the result supports removal of detectable TNF-α-containing material from the medium through the antibody-directed uptake process.
What the cell experiments show
The preprint identifies a membrane-proximal ASGPR1-binding antibody that can be incorporated into a bispecific format and used to recruit TNF-α towards cells. This is meaningful because it demonstrates a mechanism for redirecting an extracellular cytokine to an endocytic receptor, rather than relying only on conventional antibody binding or receptor blockade.
The study also provides a defined molecular starting point for further antibody-based cytokine-redirection research. The reported results are limited to HepG2 cultures, biochemical or cell-binding assays and live-cell imaging. The fluorescence experiment measured a reduction in signal in the culture medium over 90 minutes; it did not establish a downstream change in TNF-α signalling or an inflammatory outcome.
The ASGPR1 interaction site was further examined using truncation and synthetic-peptide assays. AlphaFold 3 modelling proposed an interface involving the antibody variable region, but the model is a structural prediction rather than an experimentally determined antibody–receptor structure. Whether J31 produces a functional biological effect after uptake, and how the approach behaves in primary cells or an organism, will require additional studies.