Antibody–Lectin Chimeras Turn Tumor Sugars into Immune Targets

Checkpoint blockade has reshaped cancer care, yet a large fraction of patients never respond to the antibodies now in the clinic. One underappreciated reason is that tumors wrap themselves in sugar coatings that quietly tell immune cells to stand down. A new study reframes these sugars as druggable switches rather than passive decorations. Glycomics has long known that cell-surface glycans are not merely structural—they actively negotiate immunity.

In a report from Stark, et al. in Nature Biotechnology (2026), the authors introduce antibody-lectin chimeras, or AbLecs, a bispecific architecture that converts immunosuppressive glycans into targets a therapy can hit directly. The work arrives at a moment when the field is hungry for modalities that act on the “glyco-immune checkpoint”—the interface where sialylated glycans on cancer cells latch onto inhibitory lectin receptors on immune cells.

Why Tumor Sugars Silence Immunity

Many cancers overexpress sialoglycans, the sialic-acid-capped glycans that bind Siglec family receptors on macrophages, natural killer cells, granulocytes, and T cells. Engagement of these receptors delivers an inhibitory “don’t eat me” or “don’t kill me” signal that blunts antibody-mediated destruction. Conventional tactics to interrupt this axis have stumbled. Soluble decoy receptors built from lectin binding domains fused to an antibody Fc bind their glycan ligands only weakly, with dissociation constants in the micromolar-to-millimolar range that are far too loose for a therapeutic. Enzymatic sialidases that strip sialic acid systemically, and monoclonal antibodies against individual Siglecs, are entering the clinic but carry safety concerns—untargeted blockade can trigger immune-related adverse events in a substantial share of patients. The core gap is the inability to block a specific immunomodulatory glycan where it matters, on a defined cell, without dragging the whole sialome down with it.

A Chimera That Binds Glycans and Targets a Cell

The AbLec solves this by fusing two functions into one molecule. One arm is a conventional tumor-targeting antibody fragment; the other is a glycan-binding domain borrowed from an inhibitory lectin receptor, acting as a “decoy” that grabs the same glycans the native receptor would, but with a twist—it is tethered to the tumor cell through the antibody arm. Because the binding domain is presented at the cell surface in the context of the antibody, it engages glycans at nanomolar concentrations, orders of magnitude tighter than a free decoy receptor. The protein self-assembles through established knob-into-hole Fc engineering in a human IgG1 scaffold, so a T7 AbLec (trastuzumab against HER2 paired with the Siglec-7 binding domain) and a T9 AbLec (the same antibody with the Siglec-9 domain) can be produced as defined bispecific reagents. Precise Sialic Acid Analysis of the target glycans, and mapping of the epitope each Siglec recognizes, underpins the choice of which decoy domain to deploy.

Fig. 1 AbLecs fuse a tumor-targeting antibody domain with a lectin-derived glycan-binding decoy to block immunosuppressive glycan checkpoints at the cell surface. (Stark, et al. 2026)

Selective Blockade of the Right Glycan

In cellular assays the chimeras behaved as precise competitors. When added to tumor cells, T7 and T9 AbLecs displaced fluorescent Siglec-Fc probes from the cell surface, and each chimera blocked its cognate receptor more strongly than a non-cognate partner or the parent antibody alone. The effect rivaled that of treating cells with a sialidase to physically remove the ligands—evidence that the AbLec occupies the same glycan epitopes the endogenous receptor would use. In one elegant test, the T7 AbLec outcompeted an antibody known to bind the very sialylated CD43 epitope that Siglec-7 recognizes, confirming that the chimera and the native immunoreceptor fight over the identical binding site. This specificity is what lets the molecule interfere with one glyco-immune axis without broadly stripping sialic acid from every glycan in the microenvironment.

Amplifying Antibody Effector Functions

The functional payoff appears in standard readouts of antibody therapy. Co-culturing primary human macrophages with HER2-positive tumor cells, the researchers found that T7 and T9 AbLecs drove markedly more phagocytosis than trastuzumab or the soluble Siglec decoys. The same enhancement held across multiple donors and across cell lines with different HER2 and sialoglycan levels. Natural killer cells killed more efficiently under T7 AbLec treatment, as did polymorphonuclear leukocytes—two additional immune subsets that carry both Fc receptors and Siglecs. Importantly, the chimeras were not cytotoxic on their own; tumor cell growth was unaffected in the absence of immune cells, and the benefit dropped substantially when Fc receptor engagement was blocked, confirming that the effect depends on recruiting immune cells through the antibody arm.

Detailed N-Glycan Profiling and O-Glycan Profiling of the target cells helps explain which sialoglycoforms are responsible for Siglec engagement, information that could guide future AbLec design. Beyond profiling, full Glycomic Characterization of tumor models provides the substrate map a decoy domain must cover.

Fig. 2 T7 AbLecs enhance phagocytosis and cytotoxicity of tumor cells by primary human immune cells and reduce tumor burden in a humanized mouse model. (Stark, et al. 2026)

Acting at the Immunological Synapse

The most striking result is where the blockade happens. Immune synapses—the tight contacts formed between an immune cell and its target—are precisely where Siglecs would otherwise cluster and deliver their inhibitory signal. The chimeras, tethered to the tumor cell by the antibody, exclude Siglecs from that synapse and shift receptor binding from a strong bivalent mode to a weak monovalent one that rapidly dissociates. A computational model trained on the binding data supported this mechanism: by reducing binding valency, AbLecs disrupt the receptor clustering thought necessary for inhibitory signaling.

This local action beats systemic approaches. Benchmarked head-to-head, a single T7 AbLec outperformed the combination of trastuzumab plus a Siglec-7 or Siglec-9 blocking antibody, and matched trastuzumab paired with a sialidase. The combination of the two arms within one molecule was essential—simply mixing the antibody with a soluble Siglec-Fc did not recapitulate the effect. The AbLec also acted in concert with blockade of the CD47 “don’t eat me” checkpoint, pointing to combination strategies that could extend benefit to more patients.

Signaling Insights from Phosphoproteomics

To understand how the chimera reprograms immune cells, the team profiled phosphorylation across the macrophage proteome after treatment. Compared with trastuzumab alone, AbLec treatment dampened phosphorylation of proteins in the Rab11a endosomal-recycling complex, a change consistent with more phagosomes maturing into degradative compartments. The chimera also enriched a sweep of pro-inflammatory signaling signatures, including upregulation of CDK2 activity, a kinase whose signaling supports macrophage activation and is held in check by inhibitory Siglec signalling. The pattern was not simply the sum of antibody plus Siglec blockade, suggesting a synergistic program arising from the fused architecture.

A Modular Platform for Many Targets

Because the design separates the targeting antibody from the decoy domain, new AbLecs can be assembled like parts. Swapping trastuzumab for rituximab (anti-CD20) or cetuximab (anti-EGFR) yielded chimeras that worked against B-cell and EGFR-driven lines, respectively, and a trastuzumab paired with a Siglec-10 domain extended the concept to a different inhibitory receptor. Crucially, the boost persisted even at low antigen density, a clinically relevant scenario where standard antibodies often lose traction. The modularity implies that, once a tumor’s Glycan Release profile and its antigen are known, an appropriate decoy can be matched to the dominant immunosuppressive glycan.

Chemoenzymatic Glycan Derivation and Sialic Acid Derivation routes supply the defined sialoglycan standards needed to validate which epitopes each decoy domain should capture—an enabling capability for platform expansion.

Dual Checkpoint Blockade

The same plug-and-play logic was extended to simultaneous blockade of protein-based and glycan-based checkpoints. Pairing an anti-PD-1 antibody with a galectin-9 binding domain produced a chimera that blocked both PD-1 and the TIM-3/galectin-9 axis on T cells at once; pairing an anti-PD-L1 or anti-CD47 antibody with a Siglec-7 domain did the same for those pathways. In each case the fused molecule occupied the binding sites of both parent agents, confirming dual action from a single bispecific. Such constructs could attack orthogonal suppressive pathways that singly targeted drugs leave intact.

Proof in Vivo

The translational signal came from a humanized, immunocompetent mouse model, where T9 AbLec significantly reduced metastatic tumour burden compared with the parent monoclonal antibody, and most comparator regimens tested; T7 AbLec showed a consistent trend toward lower burden that did not reach statistical significance in this model. Together with the in vitro data, this positions AbLecs as a candidate modality that acts on a distinct regulatory axis and therefore complements—rather than duplicates—existing checkpoint inhibitors.

Outlook

Many human cancers are driven by Siglecs or galectins and carry surface antigens amenable to targeting, so the addressable space for AbLecs is broad, spanning colorectal, prostate, pancreatic, glioblastoma, and melanoma settings. Open questions remain about durable responses, combination sequencing with approved immunotherapies, and which glyco-immune axes matter most in each tumor type. Still, by turning the tumor’s own sugar cloak into a point of therapeutic attack, AbLecs offer a modular blueprint for glycan-directed immunotherapy.

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Reference

1. Stark, J. C., et al. (2026). Antibody-lectin chimeras for glyco-immune checkpoint blockade. Nature Biotechnology. DOI: 10.1038/s41587-025-02884-6.